Week 2, Chapter 62 - Gasoline Fuel Systems Flashcards
What kind of injection system is more prevalent today?
Multipoint Fuel Injection (MPFI)
What kind of injection system places the fuel injectors in the cylinder head near the spark plugs?
Gasoline Direct Injection (GDI)
What is needed to determine the proper quantity of fuel to be injected?
The PCM/ECM
Fuel needs to be ___________ as it enters the cylinder
Vaporized
___________ of fuel helps it mix with air better
Atomization
Modern gasoline-powered vehicles use _____ systems
EFI (Electronic Fuel Injection)
Pressure differential is central to _____ fuel systems
All
What are some sub-systems of modern fuel injection systems?
- Fuel supply system
- Air supply system
- Fuel metering system
It is highly explosive to mix air with what?
Gasoline Vapor
What generally occurs in lower pressure fuel systems, or in systems that have too low of fuel pressure?
Vapor lock
Gasoline must be enhanced with different additives such as…
Detergents
What helps to keep the fuel system clean?
Detergents
What two methods are used to measure the octane rating of fuel?
- Research Octane Number (RON)
- Motor Octane Number (MON)
Higher octane does NOT mean…
Higher energy output
Engines perform best when used with octane rating recommended by the…
Engine Manufacturer
Carburetion works off pressures ______ atmospheric pressure
Below (Vacuum)
Fuel injection works off pressures _______ atmospheric pressure
Above
_______ is now boosted with additives of ethanol, aromatic hydrocarbons, and ether chemicals
Octane
_________ is a violent collision of flame fronts in the cylinder, caused by uncontrolled combustion
Detonation
What occurs before normal ignition?
Pre-ignition
What occurs after normal ignition?
Detonation
Many engine management systems use _________ to detect detonation
Knock sensors
What is a running-on or dieseling engine?
An engine that keeps running after it is switched off
What happens when a hot spot in the cylinder ignites the mixture before the spark plug?
Pre-ignition
What happens when a hot spot in the cylinder ignites the mixture after the spark plug causing a second flame front?
Detonation
What kind of unit is a fuel injector?
Solenoid
What is the shelf life of gasoline?
6 months
What can be caused by a high idling speed, an overheated engine, too many carbon deposits in the chamber, or use of a gasoline with an octane rating that is too low?
Dieseling
Fuel-injected vehicles do not experience dieseling unless…
There is a leaking injector when the ignition is turned off
What kind of air-fuel mixture has more air than fuel?
Lean
What kind of air-fuel mixture has less air than fuel?
Rich
A slightly _____ air-fuel mixture gives good fuel economy and low exhaust emissions
Lean
A slightly ______ mixture can produce more power, but the extra fuel it uses steps up fuel consumption and greatly increases emissions
Rich
Extremely ______ mixture can foul spark plugs and increase carbon deposits in the combustion chamber and exhaust
Rich
What describes the chemically correct air-fuel ratio necessary to achieve complete combustion of the fuel and air?
Stoichiometric Ratio
What is the stoichiometric air-fuel ratio?
14.7 lb of air to 1 lb of fuel
What sensor is used to indicate the amount of oxygen in the exhaust to help the PCM maintain the stoichiometric ratio?
Exhaust Gas Oxygen Sensor
Atmospheric pressure _________ with altitude
Reduces
A pressure gauge indicates only pressure __________ atmospheric pressure
Above
Gauge Pressure + Atmospheric Pressure =
Absolute Pressure
Pressure below atmospheric pressure is called __________
Vacuum
At wide-open throttle, the vacuum is much less and the pressure in the manifold does what?
Rises to atmospheric pressure
A vacuum gauge can be calibrated in inches of mercury in a scale reading from what?
0” to 30”
Some engine management systems use a ____________ or the MAP sensor KOEO to determine atmospheric pressure
Barometric Pressure Sensor
What is the primary reservoir of the onboard fuel supply?
Fuel Tank
Modern emission controls prevent tanks from…
being vented directly to the atmosphere
A liquid-vapor separator prevents liquid fuel from…
Reaching the charcoal
Fuel filler neck can incorporate the use of a ____________________
Blowback Ball Valve
Fuel filler neck can also contain a ________________ in the event of a roll-over to prevent fuel spillage
Roll-over check ball
Modern vehicles are required by the EPA to have a non-vented _________
Gas cap
A ______________ is an electromagnetically operated switch that basically activates the fuel pump
Fuel Pump Relay
The current operating the fuel pump relay winding is typically controlled by…
The PCM
In most cases, the PCM _______ the winding when it wants the fuel pump to operate
grounds
Where is the fuel pump typically located?
Fuel tank
Electric fuel pumps can be the __________ type or ___________ type
low-pressure; high-pressure
A fuel pressure regulator maintains fuel pressure between the…
Pump and the injectors
Speed of the fuel pump is varied to maintain the correct pressure using…
Fuel pump control module and PWM
A pressure check valve in the pump does what?
Maintains the fuel pressure in the system after engine shutdown
What kind of pump chambers do electric fuel pumps use?
- Roller cell pump
- Peripheral pump
- Side channel pump
What component sends constant electrical signals to the gas gauge located in the driver information center or to the BCM
Fuel Tank Sending Unit
What is the fuel tank sending unit?
A variable resistor that is attached to a float mechanism
As the fuel level changes (in a fuel tank sending unit), so does the…
Resistance
On today’s EFI vehicles, the sending unit is incorporated with the ____________
Fuel Pump
What are the three steps in the Fuel Tank Sending Unit assembly?
- Pick up fuel from the bottom of the tank by way of the fuel pump
- Strain the fuel and pressurize it
- Report the level of fuel in the tank
What is the first line of defense of a fuel assembly and is incorporated into the end of the fuel pickup?
Filter Sock
What is the purpose of fuel lines?
To carry fuel from the tank to the engine
What 3 components are connected by the evaporative emission system lines?
- Fuel tank
- Charcoal canister
- Intake manifold
What component typically consists of a pleated paper filter housed in a sealed container?
Fuel Filter
What is the primary function of the fuel filter?
To prevent contaminants from reaching the injectors
Where are fuel filters typically found?
On the frame rail, near the tank, or in the tank
The __________________ can also serve as a mounting place for the fuel pressure regulator usually located on the outlet side of the fuel rail
Fuel Rail
What are fuel rails usually sealed by?
- Flared ends
- high-pressure O-rings
- banjo fittings
What is the first thing you should do if you suspect an electrical issue?
Check the fuse
___________ is important. __________ is critical for performance.
Pressure; Volume
Some vehicles have a ___________________ which uses a one-way valve to hold pressure in the system while the pressure tester is connected and disconnected to the fuel rail
Schrader Valve
What should you do before handling a high pressure GDI (or any) fuel system?
Relieve pressure before removing components
All sealing components are _________ on the high-pressure side of GDI systems
One-time use
The EFI pressure regulation system can be a _______________, also known as a returnless type
Circulation type
In a _______________________, fuel is drawn from the tank by a fuel pump and delivered to solenoid-operated injectors
Circulation system
On most modern circulation/returnless systems, the pressure is controlled by the ________________ and the pump only delivers the amount of fuel being injected
Speed of the pump
On slightly older systems, a __________________ mounted on the fuel rail, incorporates a diaphragm-operated valve
Fuel pressure regulator
The fuel pressure regulator inlet is connected to the fuel rail and an outlet does what?
Lets fuel return to the thank
A _____________ and ____________ determines the exposed opening of the outlet and the amount of fuel that can return
Control diaphragm; pressure spring
The strength of the ____________ determines fuel pressure in the fuel rail
Pressure spring
A typical fuel pressure regulator uses _________________ to maintain a constant pressure drop across the fuel injector
Intake manifold vacuum
No hot fuel is returned to the tank in a returnless system. This results in less ___________________
Evaporative emissions
On some GDI systems there is a solenoid on the high-pressure mechanical pump that allows fuel to return to the tank. This is often referred to as the __________
Spill valve
What component has a spring-loaded, electric-solenoid spray nozzle?
Fuel injector
The fuel injector nozzle can be a…
- Rotating disc style
- Pintle style
- Ball-valve style
The response time to lift the injector needle to the fully open position is about ___________
1 Millisecond
Also known as single-point injection or central-point injection
Throttle body injection
In TBI system, fuel is sprayed into the top center of the throttle body and then _________ with the incoming filtered air
Atomized
What injection system includes these points…
- Simplest type of EFI system
- Require only one or two injectors
- Central injector is normally triggered on every ignition pulse
- Fuel pressure and flow is provided by an electric fuel pump
- Operate between 15 and 20 PSI
Throttle Body Injection (TBI) systems
Commonly referred to as Multi-port Fuel Injection
Multipoint fuel injection
What fuel system includes these points…
- A fuel injector is used for each cylinder
- Each injector is located in the intake manifold facing the intake port and valve in the cylinder head
- Each injector is connected to the fuel rail
Multipoint fuel injection system
Most _______________ are supplied with constant battery voltage when the ignition key is in the Run or Crank position
Electronic Fuel Injectors
Fuel pressure and flow is provided by a(n) _______ fuel pump
Electric
Injectors can be triggered at the same time or in groups; this is known as ______________
Batch/gang firing
Operates the injectors _____ per cycle
Twice
What fuel injection system incudes these points…
- Grouping the injectors allows for a less powerful processor in the PCM and fewer drivers inside
- Fewer terminals coming out from the PCM and fewer wires in the harness
- This was a common system in the late 80’s and early 90’s
Simultaneous Fuel Injection
In sequential fuel injection, injection occurs in the sequence of the ______________
Firing order
In sequential Fuel Injection, each injector typically opens _____ in each cycle to deliver the fuel needed
Once
In sequential fuel injection, the crankshaft position sensor informs the PCM the location of the _____________
1 Cylinder
In sequential fuel injection, the camshaft position sensor informs the PCM for top dead center compression cylinder __
1
In sequential fuel injection, if cam signal is lost, the PCM may go into _______________
Batch fire mode
In GDI, since fuel is sprayed directly into the cylinder, the fuel itself has a ___________ effect
Cooling
What are the 4 modes of operation of a GDI system?
- Stratified Charge
- Stoichiometric
- Full Power
- Catalyst Heating
GDI systems are a ________ injection event
Multi-pulse
GDI fuel systems can either be ____________ variety or ____________ variety
Low pressure; High pressure
GDI low pressure systems operate with about _________ PSI
35-70
GDI high pressure systems operate up to as much as _______ PSI
3,000
It is critical to use gasoline with adequate ____________
Detergents
To reduce ______________, use a high-quality motor oil specified for the vehicle and change the oil at the recommended intervals
Carbon Buildup
Low-speed pre-ignition can be reduced by using quality ____ that is specified by the manufacturer
Oil
The carburetor system is a ____________ fuel delivery system
supply-and-demand
Traditionally, fuel pumps for a carburetor-type fuel system were a _________________ pump
Diaphragm-type
Carbureted fuel systems have a ____________ where a float and needle valve control the fuel level
Float bowl
In a _______________ system, the fuel pump is usually mounted on the cylinder head or the engine block
Mechanical Fuel Pump
A mechanical fuel pump is _________ operated by an eccentric on the camshaft
Diaphragm
When _____ fuel is needed, pressure builds up in the fuel line to the carburetor and in the pumping chamber
Less
As the fuel circulates, it _____ the fuel pump and lines, reducing the chance of vapor lock
Cools
In a low-pressure electric fuel pump, the magnetic field energizes an armature that does what?
Pulls down the diaphragm
In low-pressure electric fuel pump system, the armature is released and the diaphragm spring forces up the diaphragm, which does what?
Forces fuel out of the pump
