190203e Advanced Mechanical Fuel Injection Systems Flashcards
What changes the amount of fuel metered per injection in a port and helix?
By rotating the plunger, which changes its effective pumping stroke.
What two basic components make up the port and helix pumping element
Barrel and plunger
When the outlet port in the rotor & the injector nozzle outlet port align in a opposed plunger injection pump, what’s happening ?
Injection
How is plunger rotation controlled in a multi-plunger port and helix injection pump?
It is controlled by the control sleeve, gear and fuel control rack. Rack position is determined by throttle position and governor action .
When the charging port on the rotor aligns with the fuel inlet port in a opposed plunger injector pump, what’s happening ?
This is called “loading”
Where would you commonly find timing marks for positioning the engine
On the flywheel or the damper
List three effects of incorrect fuel injection pump timing
Reduced feel economy, excessive exhaust smoke emissions and reduced performance (poor starting and low-power)
What must you check on a four stroke engine when inserting a timing pin to ensure number one cylinder is on compression stroke
Remove valve cover and insure both valves are closed
Why should you always rotate the engine in the normal direction of rotation during injection timing procedures
In order to remove geartrain lash that could affect timing accuracy
Immediately after completing injection pump installation what must you remember to do to the pump and flywheel
Remove the timing pins to prevent damage
What effect does a cracked AFRC diaphragm have an engine
Reduced power output
What are four parts in the pumping element in the opposed plunger fuel injection pump
A rotor, hydraulic head, a pair of opposed plungers and cam ring
What component does an opposed plunger fuel injection pump look like on a gas engine
The fuel injection outlet fittings have a circular pattern or distributor shaped arrangement
True or false. In in a opposed plunger injection pump, high-pressure fuel is forced to the injector when the plungers are pushed apart by the cam ring lobes
False. Cam ring lobes push the plungers together
What effect does rotating the metering valve of an opposed plunger fuel injection pump have
The amount of fuel that enters the pumping element changes
As pump speed increases what is used to advance the timing
Fuel transfer pressure
Can you adjust the timing of unopposed plunger fuel injection pump while the engine is running
Nope. Personal injury and mechanical damage will occur
What are three major components that make up a fuel injector assembly
Nozzle body, nozzle assembly and nozzle retaining ring
What are two basic types of hydraulically operated fuel injection nozzles
Multi hole and pintle
What happens to an engine when you have a plugged or restricted return line on an opposed plunger injection pump pump
The engine shuts down or fails to start
What keeps the nozzle needle valve of a hydraulically operated fuel injector closed
Spring pressure
True or false. Pencil type fuel injectors allow the engine manufacturer to have cylinder heads with very small access passages for the fuel injectors
True
Identify three factors that affect the operation of the fuel injector and have a negative influence on fuel injector service life
Water, dirt and high heat loads
The spray pattern at the nozzle tip is determined by the nozzle manufacturer and is created for specific engine combustion chamber design. True or false
True
What precautions must you take when removing a fuel injection line in order to avoid disturbing or damaging the fuel injection pump or the fuel injector
Use two wrenches. Hold one in place and turn the other
What action must you take prior to loosening or removing injection lines or fuel injectors from an engine
You must clean around the injector and fittings to avoid contamination
What method would you use to check fuel lines for leaks without creating a personal safety hazard
If checking for high-pressure use a piece of cardboard
List the three basic functions of a governor
Control low idle speed, control high idle speed and maintain a constant speed
Define the term low idle speed
It’s the lowest no-load speed at which the engine will run without operator input
true or false - use the holddown Fasner to pull the injector into the machine opening in the cylinder head
False injectors should slide in easily and not be forced
True or false. High idle and full load speeds are only the same when speed droop is zero
True
True or False. Governor stability refers to how quickly (or slowly) the engine governor reacts to changes in engine speed.
False. It’s the ability of a governor to maintain a required engine speed without hunting or surging.
What are three conditions under which the governor may not be able to control engine speed
Load pushing the vehicle, engine overloaded and engine exposed to outside fuel sources (airborne)
What are two governor classifications typically used in mobile equipment
Limiting speed and variable speed
True or false. As engine speed increases, the flyweights oppose the force of the governor spring
True
Pintle fuel injection nozzles are ________ hole design
Single
True of false - Pintle nozzles have the same opening pressure as Multi-hole design fuel injector ?
Ture they both open at (1400-2500 psi)
What should be done after each fuel line is removed?
Immediately cap the line and fuel inlet fitting with clean, tight fitting cap type plugs
What should NOT be done to the fuel line
Should NOT attempt to straighten or bend lines
Purpose of fuel injection line clamps?
Eliminate vibration and prevent damage from chafing
Why should injection lines be equal in length?
Ensures that an equal volume of fuel is in each line to prevent injection delay from cylinder to cylinder
What can happen if you do not remove the copper washer from the fuel injector or cylinder head?
The injector position will change when you install the new copper washer.
What will the governor regulate?
RPM and power output
What does the governor continually regulate?
Engine RPM, reacts to RPM change, controls the fuel system to adjusts metering as required
In most engines where are the fuel injector assemblies mounted
They are mounted in machined openings in the cylinder head
The nozzle is seated on a soft metal washer list two factors that this provides
1) pressure tight seal from the combustion chamber
2) transfers heat from the injector to the cylinder head
What can happen when a fuel injector nozzle is exposed to dirty fuel ?
- erodes the calibrated holes
- destroys the sealing surface between needle valve and nozzle body
As transfer pump rotor speed increases what else increases?
Volume and pressure increase proportionately
A portion of transfer fuel fills the pump housing, where a return line check valve regulates pressure to approximately?
4 PSI
A restricted return line can cause what?
Engine shutdown or failure to start
How many lobes does cam ring have?
The pumping element revolves within a cam right that usually has the same number of lobes of the engine has cylinders
What’s the function of the metering valve?
The metering valve controls the amount of fuel delivered to each fuel injector on the engine and is connected to the governor and throttle assembly
Identify two governor classifications used in mobile equipment.
limiting speed
variable speed
List five functions of a fuel injection system.
- inject fuel at correct time
- inject fuel at the correct rate
- atomized the fuel
- meter the fuel
- inject the fuel at high enough pressure for proper penetration
Diaphragm and plunger type fuel transfer pumps are operated by an __________.
eccentric on the engines camshaft or the fuel injection pump camshaft
Define “penetration” in regards to a fuel injection pump?
penetration refers to the ability of the fuel spray to reach all areas of the combustion chamber
What does “metering” mean in a fuel injection system?
to supply exactly the right amount of fuel for all engine speeds and loads
What does “atomization” mean?
to break the fuel up into tiny droplets small enough to vaporize readily with the heat of compression
Identify two basic type of hydraulically operated injection nozzels
mulihole
pintle
List three major components that make up a fuel injector assembly.
nozzle
nozzle body
nozzle retaining nut
List three basic functions of a governor.
control low idle
control high idle
maintain a constant speed
