Engines - Fuel, Induction, Ignition and Starting Systems Flashcards
Out of gasoline, natural gas, propane and diesel, which fuel has the highest heat value?
diesel
What effect does the heat content of a fuel have on the power of an engine?
heat content ↑ = power ↑
True or false:
1 calorie is the amount of heat required to heat 100g of water 1℃.
false;
to heat 1g of water 1℃
True or false:
1 BTU is the amount of heat required to heat 1 lb of water by 10℉.
false;
1 lb of water 1℉
On what types of engines is octane rating important?
spark ignition engines
The _______________ rating of fuel refers to the ability of the fuel to resist ignition due to compression.
octane
low octane number = easier to ignite due to compression
The _______________ (lower/higher) the octane number, the more the fuel can resist self-ignition.
higher
What effect does a high octane rating have on a fuels burn rate?
octane rating ↑ = burn rate ↓
octane ratings give an indication of how well the fuel resists combustion
What type of fuel has an octane rating of 100?
propane
What type of fuel has octane ratings of between 86 to 91?
gasoline
What type of fuel has octane rating over 100?
natural gas
The _______________ rating of fuel is the ability of a fuel to ignite easily under compression.
cetane
What type of engines is cetane rating important?
compression ignition engines
The higher the cetane rating, the easier the fuel ignites under compression.
The _______________ (lower/higher) the cetane rating of fuel, the easier it is to ignite under compression.
higher
low cetane number = harder to ignite under pressure
In engines, what is flame propagation?
how the flame travels through the air-fuel mixture in the combustion chamber
*this is the key to correct ignition timing
What effect does ignition delay have on ignition timing in engines?
it dictates how much BTDC the ignition needs to happen;
this is done so that peak pressure rise in the cylinder occurs just as the piston reaches TDC
What effect does octane rating have on ignition timing?
octane rating ↑ = greater ignition delay = greater the ignition advances from TDC
octane rating indicates how well the fuel will resist burning ⟶ the more time it will take for the flame front to propagate out and burn all of the fuel
When is it desirable for the flame front inside an engine to burn rapidly and create peak pressure inside the cylinder?
TDC;
this allows most of the pressure to be used on the power stroke
_________________ (advancing/retarding) timing moves ignition further ahead of TDC.
advancing
_________________ (advancing/retarding) timing moves ignition closer to TDC.
retarding
With this type of SI engine combustion, there is a slight delay, followed by ignition, which starts from the plug and travels to the opposite side of the combustion chamber until combustion is complete.
normal combustion
With this type of SI engine combustion, a second ignition occurs in the combustion chamber before the primary spark, resulting in two flame fronts that cause a very fast burn of the fuel, leading to an abnormal pressure rise in the combustion chamber and subsequent knocking.
pre-ignition
What causes pre-ignition in an engine?
hot spots in the combustion chamber
What three things commonly cause hot spots in an SI engine?
- spark plugs with the wrong heat range
- glowing carbon deposits
- sharp edges ⟶ these do not cool well
- What effect does pre-ignition have on an engine?
- Why is this?
- part breakage and loss of power
- the burn tries to drive the piston back to BTDC
With this type of SI engine combustion, a normal ignition occurs, but the pressure on the opposite side of the combustion chamber becomes high enough to cause self-ignition of the fuel, resulting in two flame fronts in the combustion chamber and an excessive pressure rise in the cylinder.
detonation
With SI engines, does detonation occur before or after normal ignition of the air-fuel mixture?
after;
its caused by excessive pressures on the side of the cylinder opposite of the ignition, causing self-ignition of the fuel in that area
What are the four main causes of detonation in an engine?
- low octane fuels
- lean mixtures
- overheating of the engine
- initial timing set too early
In gasoline fuel systems, the liquid fuel must be metered, atomized, and mixed with air before it enters the engine cylinders. What are two methods of doing this?
- carburetor
- electronic fuel injection
True or false:
The average mixture for gasoline engines (by weight) is from 14 to 16 parts of air to 1 part of fuel.
true
What are the four basic parts of a carburetor fuel system?
- carburetor
- fuel pump
- fuel tank
- fuel filter
The __________________ atomizes fuel from the storage tank and mixes it with air in the proper ratio.
carburetor
The _______________ _______________ (2 words) is where the air enters the carburetor.
air horn
The _______________ maintains the correct level of fuel in the float bowl of a carburetor.
float (with needle valve and seat)
The ________________ _______________ ______________ (3 words) allows fuel to be drawn from the float bowl into the air horn of a carburetor.
main discharge tube
The _______________ is a restriction in the air horn that creates a low-pressure area in a carburetor, causing gasoline to travel up the discharge tube into the airstream.
venturi
The ____________ ____________ (2 words) is a hole or holes in the discharge tube of a carburetor that adds air to the gasoline so that the gas stream is broken up into smaller droplets for easier vaporization in the air horn.
air bleed
The ____________ ____________ ___________ (3 words) controls the amount of fuel that can go up the discharge tube of a carburetor.
metering jet size
The ______________ _____________ (2 words) is the speed control mechanism for the engine with a carburetor, controlling the amount of air and fuel that enters the cylinders.
throttle valve (butterfly valve)
The _______________ is used to block off the air horn of a carburetor, increasing the amount of fuel that enters the air horn to create a richer air-fuel mixture.
choke
What component of a carburetor determines how much of the air-fuel mixture enters the engine, directly affecting the speed and load the engine carries?
the throttle valve
This type of fuel injection system sprays the fuel directly into the engine intake system in a cone-shaped pattern for maximum distribution and atomization.
computer controlled electronic fuel injection
What are the two basic methods for metering the fuel in electronic fuel injections systems?
- continuous injection with varying fuel pressures
- opening in the injector in pulses
The _____________ _______________ is the computer that gathers information from all the sensors in a fuel injection system, determining the amount of fuel to be delivered by the injector.
control module (microprocessor)
The ______________ _______________ (2 words) contains the butterfly valve that determines the amount of air allowed in the system of an electronic fuel injection system.
throttle body
What controls the throttle body on a stationary electronic fuel injection system?
the governor
What controls the throttle body on a mobile application electronic fuel injection system?
the operator
*think gas pedal
The ______________ _______________ ______________ (3 words) tells the computer the position of the throttle butterfly valve, and is an indication of the amount of air coming into an electronic fuel injection system.
throttle position sensor
The ______________ ________________ ______________ (3 words) determines the fuel manifold or injection pressure in an electronic fuel injection system.
fuel pressure regulator
In an electronic fuel injection system, the _______________ admits fuel into the air stream as the engine is running, and is done by a steady, cone shaped stream or by pules, depending on the system.
injectors
In an electronic fuel injection system, the ______________ _______________ _______________ sensor tells the computer what the absolute pressure is in the manifold (vacuum) and is a direct indication of engine load.
manifold absolute pressure sensor
What does the manifold absolute pressure indicate on an electronic fuel injection system?
engine load
This electronic fuel injection system component has a heater attached to it so it can indicate oxygen content in the exhaust manifold sooner than the non-heated sensor.
heated oxygen sensor (exhaust gas)
This electronic fuel injection system component is attached to the block or the head to indicate whether there is pre-ignition or detonation.
knock sensor
In a continuous fuel injection system, what changes the amount of fuel that is being injected?
the pressure in the fuel rail;
this is varied depending on engine requirements
With a pulse fuel injection system, where is the fuel injected into?
the engine manifold;
remember with SI engines, the intake valve allows an air-fuel mixture, so the fuel must be mixed before this point
With a continuous fuel injection system, where is the fuel injected into?
the intake manifold or the intake port (port injection)
What is a wideband oxygen sensor?
an oxygen sensor that measures oxygen-to-fuel ratios over a wider band (lean to rich)
What are the two classifications of natural gas fuel systems found on engines?
- carbureted
- fuel injected
- Which type of fuel system is not common on natural gas engines?
- Why is this?
- fuel injected
- natural gas is already in a gaseous state
What determines the type of natural gas filtering required for each engine?
the source of the fuel
On a natural gas engine system, where is the filtering system placed?
before the regulating or metering components
Why is it critical to follow natural gas carburetor linkage set-ups, even when the final linkage may look like it has too many odd angles (2 reasons)?
- the governor has a specific range of travel
- throttle response;
there is a greater response to a change in throttle position from idle to half throttle than there is from half throttle to full throttle
With natural gas carburetor linkages, the linkages is set up so that there is a greater response to a change in the throttle position from idle to half throttle than from half throttle to full throttle. Why is this?
to prevent the governor from over-correcting for engine and load speed changes (hunting)
*small movements when at running speeds and loads will result in small movements on the throttle
**high gain at the beginning followed by changing to a low gain at over half speed
- How should the carburetor linkages be tested for balance on natural gas V-type engines after they have been set?
- Why is this critical on V-type engines?
- with a manometer attached to the manifold
- V-type engines have two manifolds ⟶ if not equal, one bank of cylinders will constantly overload
*balancing the engine ensures that all cylinder carry and equal amount of load
What effect does a leaking throttle shaft seal have on a natural gas engine?
it allows unfiltered air into the engine;
this can wear engine rings and liners, along with leaning out the air-fuel mixture
Due to the expansion rate of propane, it is mandatory to not fill propane tanks more than _____% of capacity.
80%
On a LPG engine system, this component only allows fuel to the engine once engine vacuum is high enough or when the solenoid in the fuel valve is supplied with power.
fuel lock and filter
On a LPG engine system, where is the fuel lock and filter located within the system?
between the storage tank and the converter
On a LPG engine system, this component prevents fuel from flowing if the engine has stopped, stalled, or in the event of an accident.
fuel lock and filter
On a LPG engine system, this component is used to reduce the high-pressure (tank pressure) liquid propane to a low-pressure vapour.
converter/regulator
On a LPG engine system, what is a vaporizer?
same as a converter/regulator
What are the three chambers of an LPG converter/regulator and what are their purposes?
- primary chamber ⟶ emits propane into the component
- secondary chamber ⟶ creates the pressure drop between the primary and secondary chamber needed to change the propane into a vapour
- heat exchanger ⟶ used to heat up the propane and component to prevent freezing
How is the heat exchanger on an LPG converter/regulator heated?
with engine coolant;
without this heat, the converter/regulator would freeze up and transmit liquid flow through the unit to the mixer
What happens to the LPG if the heat exchanger on a converter/regulator freezes up?
liquid propane is supplied to the carburetor (mixer) rather than a gas
What are the two types of carburetors (mixers) found on LPG engines?
- air valve carburetors
- spray bar carburetors
Which type of LPG fuel component is similar to a natural gas carburetor?
the air valve mixer
A LPG spray bar mixer uses a metering valve and throttle plate simultaneously. What does the:
- metering valve control?
- the throttle plate control?
- metering valve ⟶ amount of fuel entering the air stream
- throttle plate ⟶ amount of air entering the engine intake
*this are connected through a linkage, so they open and close together
What causes the delay in ignition in CI engines?
once the fuel is injected into the cylinder, the fuel must first both vaporize and mix with the air before it can begin to burn
Why is there no throttle valve in diesel fuel systems?
air is always present in diesel systems, rather power is throttled by controlling the fuel amount;
throttle valve ⟶ controls the amount of air emitted into the cylinder
True or false:
The fuel must be injected into a CI engine at the precisely right time and under high pressure to penetrate, atomize and mix the fuel in the compressed air.
true;
timing is more critical in a CI engine vs. an SI engine
This type of engine has an initial ignition delay, followed by a rapid uncontrolled combustion, and then finally a controlled combustion.
CI engines
This type of engine has an initial ignition delay, followed by a second stage of combustion.
SI engines
What effect does having a low compression have on a diesel engine?
they never achieve the heat required to cause the fuel to ignite;
higher compression = higher air temperatures
Why are starting aids required on diesel engines to start them in cold weather?
the cylinders absorb much of the heat generated from the compressing air;
without start aids, the engine wouldn’t heat up enough to allow for combustion
This component of a CI engine fuel system meters the fuel and brings the pressure necessary to overcome the injector’s set pressure.
the injection pump
*this is a precise, accurately built, expensive piece of equipment
This component of a CI engine fuel system delivers the high-pressure fuel into the combustion chamber, and must open and close precisely while being able to withstand the heat and pressures of combustion.
the injectors
What are the three fuel lines found on injection fuel systems and what are their purposes?
- low-pressure suction line ⟶ moves fuel from the tank to the transfer pump to the injection pump
- high-pressure fuel lines ⟶ move fuel from the injection pump to the injectors
- return line ⟶ injection pump or injectors back to the tank
What kind of engine has an injection fuel system?
CI engines;
these fuel systems are designed to inject the fuel at high pressures into the combustion chamber
What are normally operating pressures seen on the high-pressure fuel lines on injection fuel systems?
1000 to 5000 psi;
be wary of injection injuries
What are the two common types of fuel injection pumps/systems?
- mechanical injection/mechanical control
- mechanical injection/electronic control
This type of mechanical injection/mechanical control fuel system has one high-pressure pump plunger that distributes and pumps fuel to a distribution head, which is then diverted to each of the injector nozzles at each cylinder.
distributor fuel injection
What type of engines are distributor fuel injection systems found on?
small industrial and automotive diesel engines
This type of mechanical injection/mechanical control fuel injection system is a self-contained unit that has its own cam and plunger for each cylinder.
inline fuel injection systems
On an inline fuel injection system, what does the governor linkage control in order to change the amount of fuel delivered to the combustion chamber?
the fuel rack (control rack)
When the control rack on an inline fuel injection system is adjusted, what happens to the plunger pumps?
it rotates the position of the plunger in its bore, which changes the position of the plunger helix port for when fuel is delivered to the injector changes;
this is known as the port and helix metering method
This type of mechanical injection/mechanical control fuel injection system is similar to an inline system, except that the engine cam drives the pumping element through a pushrod mechanism.
unit fuel injection system
What are the three mechanical injection/mechanical control fuel systems?
- distributor fuel injection
- inline fuel injection
- unit fuel injection
What type of mechanical injection/mechanical control fuel system uses the camshaft to drive the pumping element through a pushrod mechanism.
unit fuel injection system
What type(s) of mechanical injection/mechanical control fuel systems use fuel racks to control the amount of fuel entering the combustion chamber?
inline fuel injection and unit fuel injection
- What types of mechanical injection/mechanical control fuel systems can be converted to use electronically controlled valves?
- How is this done?
- inline fuel injection and unit fuel injection systems
- by timing the fuel delivery by electronically opening and closing the needle valve in the injectors
What should be done in order to depressurize a high pressure injection fuel system?
isolate the fuel pump and run the engine until it stalls from lack of fuel
this burns off most of the fuel pressure inside the engine
How long should a CI engine be cranked over in order to ensure that any remaining pressure is cleared from the system after the system has been isolated and run until stall?
20 to 30 seconds;
this clears most or all the remaining pressure
What is the function of the induction system on an engine?
supply clean air at the proper temperature and quantity
What effect does inadequate air supply have on an industrial engine?
excessive fuel consumption and a loss in power
What should the intake air temperature be at for maximum efficiency of an engine?
between 15℃ (60℉) and 32℃ (90℉)
What effect does air that is too hot have on an engine?
power drops off (air is less dense = lean mixture)
What effect does air that is too cold have on an engine?
reduced compression temperatures, which results in poor fuel ignition and thermal shock to the engine
This component of an engine induction system is installed before the air cleaner to increase the service intervals of the air cleaner.
pre-cleaners
What is the most common type of filter found on induction systems on engines?
dry air filters ⟶ these tend to use pleated paper as the filtering medium
What is the efficiency of dry air filters?
99%
This component of an engine induction system directs air so that it must take a sharp corner, at which point the air encounters oil, which catches the dirt particles in the air.
oil bath air cleaners
What is the efficiency of oil bath air cleaners?
95% to 98%
What effect does using the improper viscosity of oil have on an oil bath air cleaner?
the cleaning ability will be reduced
This engine induction system component doesn’t use an element, rather it uses the speed of the air passing through a tube with a spiral inside to throw the dirt particles to the outside edge, where they are collected and emptied by a Venturi mechanism into the exhaust stack.
spiral rotor air cleaners
What is the most accurate method of measuring air cleaner restriction?
water manometer
How can dry air cleaner elements be cleaned?
by blowing them out with compressed air
- What is the maximum amount of sludge that should be allowed to accumulate in an oil bath cleaner before cleaning the filter?
- How can oil bath air cleaners be cleaned?
- no more than 1/2 of an inch
- cleaning/replacing the oil
What effect does having an oil bath air cleaner that is too small for the engine have on the filter?
oil can pull over into the engine
What effect does having an oil bath air cleaner that is too larger for the engine have on the filter?
it does not filter well due to reduced velocity
What are the two types of U-tube manometers?
- water-filled
- mercury-filled
This type of engine induction method relies on atmospheric pressure to push air into the cylinders.
natural aspiration
VE = less than 100%
This type of engine induction method uses some sort of mechanical means to push air into the cylinder.
artificially aspiration
VE = over 100%
What does supercharging or boost pressure refer to on an engine?
charging the air in the cylinder to above atmospheric pressure
This type of engine artificial aspiration uses the underside of the piston and a sealed crankcase to push air into the cylinder.
piston-type scavenging pumps
This type of engine artificial aspiration uses small gas radial turbines powered by exhaust gases to drive a radial compressor wheel on the opposite end of the shaft.
turbo chargers
True or false:
Turbochargers use positive displacement compressor wheels.
false;
they use non-positive displacement compressor wheels
This type of artificial induction method on engines is a positive displacement unit that is mostly used on two-stroke engines.
lobed blowers
This type of artificial induction method is a non-positive displacement units that look like turbochargers except that they are mechanically driven by the crankshaft.
centrifugal blowers
What effect does supercharging or boosting the air in an engine have on the engine weight and size for a given power output?
it decreases it;
less weight for the same power output when compared to a naturally aspirated engine
What effect does supercharging or boosting the air in an engine have on the fuel economy of the engine?
it improves it, especially at rated speed and power
What effect does supercharging or boosting the air in an engine have on the pollution of the engine?
it decreases it ⟶ due to the engine being more efficient
What effect does supercharging or boosting the air in an engine have on the internal stresses of the engine?
they increase
What effect does supercharging or boosting the air in an engine have on the heat of the engine?
they increase;
these engines must have piston cooling
Why are turbochargers consider more efficient when compared to centrifugal blowers or lobe blowers?
turbochargers are powered by waste gases rather than mechanically
mechanically = parasitic draw
What is turbo lag?
the delay from when engine load increases to when the turbo spools up to provide additional pressure
This component of a turbo charger receivers the hot temperature exhaust gases from the engine and directs the flow across the turbine wheel and then back into the exhaust system.
turbine housing
What is the turbine housing of a turbo charger usually mounted to on an engine?
directly to the exhaust manifold
This component of a turbo charger directs the exhaust gases at the turbine wheel.
the nozzle
This component of a turbo charger contains the impeller wheel and is used to diffuse and compress the incoming air while directing the flow of air into the intake manifold.
impeller housing
This component of a turbo charger is connected directly to the turbine shaft, a draws clean air into the inlet side of the turbocharger.
the impeller wheel (compressor)
This component of a turbo charger contains the shaft and oil passages required to lubricate the full-floating bearings on which the shaft runs.
centre housing
What are the two types of sealing ring assemblies found in the centre housing of a turbocharger?
- piston ring seals
- labyrinth seals
What is the purpose of the other fuel types that are mixed with propane for powering an engine?
Allow starting and running at temperatures below -42°C
True or false:
Diesel engines require a lower starting RPM, compared to gas engines, because of the higher compression ratios in the diesel engine.
false;
faster speed = less time for heat to be absorbed into the cylinder and cylinder heat
Why is a faster cranking time more important for cold starting CI engines?
faster speed = less time for heat to be absorbed into the cylinder and cylinder heat
this results in more heat being available to aid in the initial combustion
What component of a turbocharger is driven by exhaust gases?
the turbine wheel
- What type of material is the turbine housing on a turbocharger usually made of?
- Why is this?
- cast iron
- To withstand the heat of the exhaust gases
- What type of material is the impeller wheel and impeller wheel housing made of on a turbocharger?
- Why is this?
- aluminum
- weight savings; temperatures are cooler on this end, so the impeller wheel can be made from aluminum
*impeller = compressor
What component of a turbocharger drives the intake air?
the impeller wheel (compressor)
What three components are found in the centre housing of a turbocharger?
- bearings
- seals
- oil passageways
What are three common ways that turbochargers are cooled?
- engine oil (also used to lubricate it)
- engine coolant (through passages)
- bleeding air from the compressor side through to the turbo side
- What is the most common method of boost control on a turbocharger?
- How is it activated?
- sensing the output pressure of the compressor to operate the waste gate
- when over-boost is sensed, the actuator opens the waste gate allowing exhaust gases to bypass the turbine wheel
- What is the most accurate method of boost control on a turbocharger?
- Why is this?
- sensing output pressure of the compressor to operate the waste gate
- output pressure is a direct function of turbocharger speed
Why is it critical when first starting a turbocharged engine to not rotate the engine at high rpm’s until the engine has sufficient oil pressure?
the turbocharger is normally the last item to receive oil
*especially critical during cold-weather starting
Why is it recommended that a turbocharged engine be allowed to idle for a few minutes after heavy acceleration before shutting it down?
it allows oil (or coolant) to flow through the turbocharger and help cool down the internal parts
What are four things that the ignition system in an engine must do?
- step up the voltage in order to jump the gap of the spark plug
- send (time) the spark to the electrode at the correct moment
- be reliable (no misfires)
- operate safely in a hazardous environment
True or false:
In engines, fuel type, load, rpm, and temperature all affect when the spark is required for proper combustion.
true
This engine ignition component is a device that distributes electrical power to each cylinder in the correct sequence and at evenly spaced intervals.
distributor
This engine ignition component are mechanical switches found on distributors and magnetos that are opened and closed by a breaker cam to interrupt the current flow.
breaker points
*these are found on older automotive and industrial distributors and magnetos
What are the two common functions of capacitors on engine ignition systems?
- stabilize voltage spikes
- store and deliver power to primary circuit in modern magnetos
When referring to an engine ignition system, what is a condenser?
a capacitor
True or false:
In an engine, misfire = no ignition
true
A _____________ is a solid state device that allows current to flow in only one direction.
diode
This type of diode is a solid state voltage-regulating device that can be specified for a specific voltage or voltage rating.
Zener diodes
A _____________ is an electronic switch that is turned on by a small current to one of its connections.
transistor
True or false:
Rectifiers are like transistors.
true;
in that they are like a switch
What is a bridge rectifier?
a solid state device that converts AC into DC
In a natural gas carburetor, what keeps the diaphragm from re-closing the air valve?
airflow;
the airflow through the air intake valve keeps this valve open, which is tied together with the fuel intake valve, keeping it open
What is a normal air-fuel ratio setting for natural gas engines?
15.5:1 to 17:1
- What is the purpose of an automatic shutoff valve on a natural gas engine?
- Why is this valve important?
- a valve that shuts off the natural gas supply to the engine if the engine stalls or is shut down
- to prevent the engine from filling up with natural gas when it is not running
This component supplies the pressure to the carburetor on a natural gas engine.
the regulator
True or false:
On a natural gas carburetor, there must always be a pressure differential between the air inlet pressure and the fuel inlet pressure in order for the carburetor to work.
true
- On a natural gas carburetor, which pressure needs to be higher: the air inlet pressure or the fuel inlet pressure?
- What happens if this is reversed?
- the fuel inlet pressure
- if the air inlet pressure is higher, no fuel can enter the carburetor
What happens to a natural gas engine if the air-fuel mixture is too lean?
the engine doesn’t produce enough power
What happens to a natural gas engine if the air-fuel mixture is too rich?
after-burn and excessive temperatures;
these contribute to a shorter engine component life and higher emissions
In a natural gas engine, what keeps the fuel intake valve closed?
the spring on the air intake valve;
these valves are linked together; when one is closed so is the other
In a natural gas engine, what opens the intake fuel valve in the carburetor?
the a vacuum on the air intake valve manifold;
this lifts off the air intake valve, which is tied together with the fuel intake valve
What design component dictates the amount of fuel and air that is mixed on a natural gas carburetor?
the design of the air (fuel) valve
On a natural gas carburetor, the power mixture adjustment screw is used to change the gas flow into the carburetor. This is set with the engine operating at _________ load.
full
What is the purpose of an expansion tank on a natural gas engine system?
a storage tank used to supply fuel to the engine to prevent engine starvation if there is a sudden change in load
True or false:
To increase outlet gas pressure on a basic pressure regulator, turn the screw on top of the regulator inward to tighten the spring on the upper diaphragm.
true
True or false:
Detonation and pre-ignition can happen in both CI and SI engines.
False;
Pre-ignition cannot happen in CI engines as there is no fuel until it is injected into the cylinder
In an engine with continuous fuel injection, which of the following components ensure the AFR is correct by measuring the composition of the exhaust gasses?
oxygen sensor
Which type of fuel will purposefully detonate in the cylinder?
diesel or bunker fuel;
any type of CI engine fuel
*this is what gives a these engines their distinctive “knock”
True or false:
The combustion in a cylinder is timed to start a few degrees before top dead center to give the fuel time to burn and cylinder pressure to rise.
true
Which type of electronic fuel injection system distributes fuel into the intake manifold without interruption?
Continuous fuel injection
Which of the following components ensures an engine has the correct air fuel ratio?
A) Throttle body
B) Fuel pump
C) Distributor
D) Carburetor
D) Carburetor
True or false:
Stoichometry is the description of the ratios and amounts of two or more chemicals that are reacted together completely without any un-reacted chemicals left over.
true
Which component, in a carburetor, creates a low pressure area to draw the fuel into the air stream?
the Venturi
Which valve closes just before the compression stroke?
A) Intake
B) Exhaust
A) Intake
What component of a turbocharger prevents the pressures in an engine from becoming excessive?
the waste gate
This type of engine ignition system uses a battery for a power supply for the system, and is typical of automotive systems and some industrial engines.
battery ignition systems
This type of engine ignition system uses mechanical switches to open and close the primary circuit ignition system, and while rare now, were used on almost all ignition systems until the late 1970’s.
point-style ignition systems
switches = points
This type of engine ignition system is one that produces its own power by using permanent magnets in its own generating system.
magneto ignition systems
This type of engine ignition system use electronically activated electronic switches (transistors) to open and close the primacy circuit and other electronic devices that have no moving parts.
electronic ignitions (solid state)
True or false:
Electronic ignition (solid state) systems are maintenance-free.
true
This type of engine ignition system is a fully computerized system that has no moving parts and is capable of individual cylinder timing based on detonation and any type of advance for any speed or load.
microprocessor-type ignition systems
This type of engine ignition system is capable of remote reprogramming and self-diagnostics.
microprocessor-type ignition systems
What type of engine ignition system is capable of continuous or prolonged spark during the combustion process?
microprocessor-type ignition systems
True or false:
Flux lines (lines of force) complete a path from south to north in a magnetic field.
false;
from north to south
True or false:
Flux lines take the path of least resistance.
true
Wrapping a conductor around an iron core to form a coil create an:
electromagnet
The magnetic strength of an electromagnet is directly proportional to what two things?
- current flowing through the coil
- number of turns in the coil
What effect does the type of core have on an electromagnet?
it determines the strength of the magnet;
iron is stronger than air
What happens any time a conductor cuts across the lines of flux of a magnetic field?
a voltage is induced in the conductor
What are the two circuits found in engine ignition systems?
- primary (low voltage) circuit
- secondary (high voltage) circuit
This circuit is the low voltage part of the engine ignition system, with typical voltage ranges of 6 VDC to 30 VDC.
primary circuit
What are the five main components of a primary circuit on an ignition system?
- power source
- ignition switch
- low voltage wiring
- ignition coil primary windings
- switching devices
This circuit is the high voltage part of the engine ignition system, with typical voltage ranges of 15,000 VDC to 60,000 VDC.
secondary circuit
What are the three main components of a secondary circuit on an ignition system?
- ignition coil secondary windings
- spark plug wires
- spark plugs
- This component of an engine ignition system is a step-up transformer that converts low voltage, high current electrical energy into high voltage, low current electrical energy.
- How is the low to high voltage conversion in a coil done?
- ignition coil
- through magnetic induction
Why is such a high voltage required in an engine ignition system?
to create a spark across the electrodes of the spark plug
What are the two windings of a transformer called?
- primary winding
- secondary winding
On a step-up transformer, which winding would consists of 100 to 250 turns of heavy wire?
the primary winding
On a step-up transformer, which winding would consists of 15,000 to 40,000 turns of very fine gauge wire?
the secondary winding
This engine ignition system component houses the points and operating cam and directs the secondary voltage from the coil to the proper spark plug.
distributor
In a distributor, what is a distributor shaft?
a shaft with a cam on it, located inside the distributor which actives the points
True or false:
In a transistorized ignition distributor, a reluctor wheel or slotted disk is used instead of a cam and points.
true
This component of an engine ignition system sits at the top of the distributor shaft and carries the high-voltage current from the coil terminal in the distributor cap to each of the spark plug terminals.
the rotor
How does the rotor in a distributor work?
it turns with the distributor shaft, alternately aligning with each of the terminals for the spark plugs as the ignition points open
How are the spark plug triggers determined with a transistorized engine ignition system?
the computer ignition module determines the trigger
This engine ignition component covers the coil switching trigger devices on a distributor, sealing out moisture and dirt while also providing contact terminals for the spark plugs.
the distributor cap
On a distributor, where are the spark plug terminals located?
on the distributor cap
What is located in the centre of the distributor cap?
a terminal to which the high volt coil wire is attached
What type of wiring is required for the high-tension wiring in engines?
explosion proof wiring;
this is considered a hazardous environment
What are the two ways that high-voltage wiring in engines is made explosion resistant?
- fixed, pipe-style conduit
- flexible coverings
What is the purpose of the fixed, pipe-style conduit and flexible coverings used on high-voltage ignition wiring?
to confine any fire that occurs due to an electrical short in the wiring system
This engine ignition system component allows the high voltage from the coil to arc across electrodes, igniting the air-fuel mixture in the engine cylinders.
spark plugs
What are the four main parts of a spark plug?
- ceramic core or insulator
- threaded metal shell
- center electrode
- plug seals and crush gasket
This part of a spark plug electrically isolates the connector from the electrode.
the ceramic core or insulator
This part of a spark plug holds the ceramic core and supports the electrode.
threaded metal shell
This part of a spark plug is in the centre of the ceramic insulator, and must be a good conductor and resist high temperatures.
centre electrode
What is the heat range of a spark plug?
its ability of conduct heat away from the tip of the centre of the electrode
True or false:
The operating temperatures of an engines spark plug must be hot enough to burn off the oil film and combustion by-products that tend to collect on the tip, but cool enough that it does not cause pre-ignition.
true
What is the heat path of a spark plug?
tip of the centre of electrode ⟶ ceramic insulator ⟶ steel shell
What determines a spark plugs heat range?
the length of the heat path
What heat range would a spark plug with a short heat path have?
a cold heat range;
short path = cold plug
What heat range would a spark plug with a long heat path have?
a hot heat range;
long path = hot plug
A __________ (cold/hot) plug is good for engines that are at an idle or low load for much of the time.
hot;
this allows carbon build up on the plug to be burned off
A __________ (cold/hot) plug is good for engines that operate near maximum load for extended periods of time.
cold
In an engine, what effect can occur if a hot plug were to be used in a cold plug application?
the plug would be too hot, resulting in pre-ignition
This section of an engine’s ignition system supplies the power to the ignition system.
power generating section
What are three common sources of power used in an ignition systems power generating section?
- 12-volt battery
- magneto ⟶ generates its own power
- plant utility power
This section of an engine ignition system is the switching mechanism that connects and disconnects the power to the primary circuit of the coil, causing the primary circuit voltage to rise and collapse in order to induce a voltage in the secondary circuit.
the trigger section
How was the trigger section accomplished in older distributor and magneto ignition systems?
with a mechanically operated set of points
How is the trigger section accomplished in modern ignition systems?
electronic switches, receiving signals from a small pick-up coil and reluctor wheel (pulse design)
In an engine ignition system, the trigger section is located in the ________________ (primary/secondary) circuit.
primary (low-voltage) circuit
This section of an engines ignition system connects the power to the cylinder to be fired.
distribution section
In an engine ignition systems, automotive applications with a distributor have a distributor system in the _________________ (primary/secondary) circuit.
secondary (high-voltage) circuit
In an engine ignition system, this section contains the step-up ignition coils required to create the voltage needed to jump across the spark plug gap.
voltage increase section
When the ignition switch is in the crank or run position, voltage is present at the ignition coil ______________ (+/-) terminal.
positive
When the ignition module completes the circuit to ground, current flows through the primary circuit and magnetic field builds around the primary winding. What happens to the this field when the ignition module opens the ground to the ignition coil?
the field around the primary winding collapses, inducing a current into the secondary winding
In a distributor ignition system, where is the secondary current from the ignition coil connected to?
the distributor cap
In a distributor ignition system, where does the secondary current travel to after reaching the distributor cap?
the rotor, which sends it to the nearest spark plug terminal, and then to the spark plug
This type of engine ignition system creates its own power supply and distribute power to the coil.
magneto ignition systems
True or false:
The magnito, in an ignition system, contains the power generation section, trigger section, and distribution system.
true
What drives the magneto ignition system in an engine?
the engine cam
This type of engine ignition system is the same as a breaker point type ignition system except that the opening and closing of the primary circuit is done with an electronic switch (transistor).
electronic ignition system (distributor type)
With this type of engine ignition system, a trigger wheel with one tooth for each cylinder is used to time the voltage pulses, with a pickup coil wound around a permanent magnet mounted beside it. As the teeth move past the pickup coil the magnetic field changes, resulting in a pulse being sent to the secondary coil and spark plug.
electronic ignition systems (distributor type)
This type of engine ignition system uses crankshaft or camshaft reference magnets with Hall-effect pickup coils to trigger the primary circuit.
microprocessor type ignition systems
This type of engine ignition system is most often found on modern day industrial natural gas engines.
magneto ignition systems
What is a timing light used for when troubleshooting engine issues?
to check when voltage is sent to the spark plug
When servicing an engine, the centre electrode and porcelain tip appear slightly grey or tan in colour. What does this indicate?
the heat range of the spark plug is correct for the engine conditions and the combustion process is normal
What effect is there on an engine if the spark gap is too great?
more voltage is wasted to initial the spark, which may not last long enough for complete combustion
What effect is there on an engine if the spark gap is too small?
the intensity of the spark may not be strong enough to ignite the air-fuel mixture
If an engine uses resistor spark plugs, why is it important to not replace these with non-resistor spark plugs?
they can interfere with sensors or computer equipment
What is the reach of a spark plug?
the amount that the plug reaches into the cylinder
What two things can happen if the reach of a spark plug is too short?
- misfiring
- carbon build up on the spark plug
the electrodes are shielded from the fuel gases
What two things can happen if the reach of a spark plug is too long?
- overheating (hot plug = longer heat path)
- contacting the piston
How should the threads of a new spark plug be prepared for installation?
they should be clean and dry
How is the spark plug gap measured?
with feeler gauges
What is proper ignition timing?
A process where each spark plug fires in relation to a specific piston position.
Ignition timing is corrtect when the total force on the piston generated through ignition and combustion occurs just after the piston moves past top dead centre (TDC)
What is the first step in the basic ignition timing procedure?
Obtain ignition timing specifications required for the engine, fuel type, and rpm.
What equipment is required to achieve proper ignition timing?
A timing light and the manufacturer’s specifications for the engine.
What should you do with the timing light during the ignition timing procedure?
Connect the timing light pick up to the No. 1 cylinder lead.
Why might the timing light signal be weak?
If the lead is shielded.
What should be done if the flywheel timing inspection cover is present?
Remove it if required to access the timing reference.
What is recommended to ensure the timing indicator is legible?
Bar the engine over and locate the timing indicator.
What is necessary to do before observing the timing light’s flash?
Warm up the engine and set the required rpm.
What should you observe to perform ignition timing?
The flash from the timing light at the indicator marks on the flywheel or pulley.
What do you do if an adjustment to the timing is required?
Loosen the distributor or magneto mount and rotate slowly until the flash occurs at the specified degree TDC.
What adjustment is needed for microprocessor ignitions?
Adjust a potentiometer or dual inline package (DIP) switch.
What should be done after achieving the correct ignition timing setting?
Retighten the distributor or magneto and verify that the timing position did not change.
What is the last step after completing the ignition timing procedure?
Shut the engine down and replace any covers or accessories that were removed.
Fill in the blank: Proper ignition timing occurs just after the piston moves past _______.
top dead center (TDC)
True or False: The timing light is connected to the No. 2 cylinder lead.
False
What is the main function of the starting system?
To conveniently turn the engine over fast enough and long enough to initiate the ignition of the fuel mixture.
How does the starting system for diesel engines differ from that of gasoline engines?
Diesel engines depend on speed to develop a sufficiently high air temperature on the compression stroke to ignite the fuel.
What are the main types of starting systems?
- Electric motor
- Air start with an air motor
- Air start with direct air injection into the engine cylinders
- Hydraulic motor
What components are required for an electric starting motor system?
- Electric starting motor
- Battery
- Electrical control
- Charging system
True or False: Electric motors are the most expensive method of starting engines.
False
What are some disadvantages of electric starting systems?
- May not be safe in an explosive environment
- Require a charging system to keep the battery charged
Fill in the blank: The speed of cranking is not as critical for __________ engines because ignition is caused by spark, not compression.
[gasoline or natural gas]
What is a key benefit of electric starting motors?
They are compact, cheap and simple.
What does the engine manufacturer usually provide regarding starting systems?
Recommendations for the type of system recommended for each application.
What is the cheapest and easiest method of starting engines?
Electric motors
Which type of engine starting system requires a charging system?
Electric motor starting systems
What type of pneumatic motors are most commonly used as air starters on industrial engines?
Vane-type pneumatic motors
These motors utilize a gear drive similar to electric starters.
How does a pneumatic starting motor engage with the flywheel during starting?
A pinion on the power shaft engages the flywheel ring gear through a starter drive
This process is similar to how electric starters operate.
What is the primary advantage of using air motors for starting engines?
They are very safe in dangerous areas (no sparks or electric current)
Air starters also provide high torque.
What is a common disadvantage of pneumatic starting motors?
They are very noisy and require an air supply
A compressor may be necessary to provide the air supply.
What is the purpose of lubricators and filters in pneumatic starting motors?
To lubricate the vanes and filter out dirt for longer service
This helps maintain the efficiency and longevity of the motor.
What is the operation principle of direct air injection ignition systems in large gas engines?
Air is applied directly into the engine cylinders to force the piston down and initiate engine rotation
This is done via air start valves.
What is a significant disadvantage of direct air injection systems?
A large volume of air is required
This system also includes many extra components like piping to each cylinder’s air start valves.
What type of hydraulic motors are used in engine starting systems, and what drives them?
Wobble plate axial piston motors driven by an oil supply under pressure
These systems are not common due to the need for a complete hydraulic system.
What are glow plugs and intake manifold heaters used for in diesel engines?
To assist in starting and warming up the diesel engine
They help vaporize and ignite the diesel fuel, which is difficult to ignite when cold.
What does the indicator lamp on the instrument panel signify when using glow plugs or intake manifold heaters?
It advises the operator to wait to start the engine until the desired temperature is reached
This is crucial for effective engine starting.
What gaps must be set on a spark plug before installation?
The gap between the ground electrode and the centre electrode
True or false:
Many two stroke natural gas industrial engines use a low-pressure fuel injection system, to bring fuel into the engine cylinders (under 100 psi).
true
Propane gas is _______ times as heavy as air.
1.5 times
