Advanced Mechanical Fuel Injection Systems Flashcards
Port and helix barrel
Is retained in a fixed position in pump housing. It contains ports that allow fuel to enter and leave the pumping element.
What are the two basic components of the port and helix pumping element?
Plunger and Barrel
Port and helix plunger
Has a constant up and down stroke. Plunger rotates is barrel, this changes metering. The helix is an angular groove machined in the outside, it determines the effective stroke
What are the 4 main stages of a plunger stroke?
Bottom of stroke - Cavity fills
Port closing - Plunger is moving up BOI
Delivery - Delivery valve is opened
Port opening - EOI
The vertical groove in the plunger is what position?
The fuel shut off position
Fuel injection tubing
High pressure seamless steel tubing. all tubes off of a pump will be the same length
The delivery valve serves as a check valve to?
Retain a head of pressure
Assist in dropping fuel injection line pressure at EOI to positively close the injection nozzle
Fuel control rack
Connects the control and gear to the throttle and governor assembly. in multi-plunger pump all sleeves are indexed to a common rack.
How does the control sleeve interact with plunger?
Control sleeve is slotted and engages with plunger to control rotation during pump operation
What are 2 common names for a exhaust smoke control?
Smoke limiting control
Air fuel ratio control
What is central purpose of a exhaust smoke control?
limit fuel control rack travel until a sufficient amount of boost pressure is present
What is timing?
The procedure of synchronizing the injection pump to the engine
Prior to installing a port and helix injection pump you need to?
Rotate pump camshaft in normal direction of rotation until the timing mark on the injection pump drive hub lines up with the fixed timing mark on the pump housing
When setting for pump timing the engine should be rotated in what direction? why?
Normal engine rotation. To prevent gear train lash from affecting timing accuracy
What two companies manufacture opposed plunger pumps?
Stanadyne (Roosa Master)
Lucas (CAV)
Opposed plunger pumps are also called?
Rotary or Distributor fuel injection pumps
How is an opposed plunger pump driven?
A shaft that couples to the engine gear train
Opposed plunger transfer pump
a vane type pump is driven by the pump rotor. As rotor speed increases, volume and pressure increases proportionately.
Cam rings will have how many lobes?
Usually the same number as the number of engine cylinders
The plungers are retained by what?
Roller shoes that are held inside of the cam ring
What is the purpose of the metering valve?
Control the amount of fuel delivered to each fuel injector.
How is the metering valve controlled?
It is connected to the governor and throttle assembly
What supplies fuel to the metering valve?
The transfer pump
How is timing advanced in a opposed plunger pump?
As engine speed increases, increased transfer pump pressure acts on the piston and moves the cam ring int he opposite direction of normal fuel pump rotation to advance the timing
What method should be used to time a opposed plunger pump?
Static timing
What is the last step in timing a Lucas pump?
Line up the mark on the pump with the timing mark on the engine timing cover
After installation a Stanadyne pump can be static timed by?
lining up the marks in the timing window on the side of the pump housing
The maximum fuel delivery of an opposed plunger pump is set by?
Adjusting the roller to roller dimension of the pumping element
The pumping elements of an opposed plunger pump include?
Rotor, Hydraulic head, Shoes & rollers, Plungers and Cam ring
Spraying cold water on an injection pump could cause it to?
Seize
A fuel injector consists of what 3 major components?
A nozzle holder
A nozzle assembly
A retaining nut
Nozzle holder
Sometimes referred to as the fuel injector body, positions the fuel injector assembly in the head. A spring in the fuel injector controls the nozzle opening pressure
What are the 2 major components of the nozzle assembly?
Nozzle body
Needle valve
What are the two basic designs of hydraulically operated fuel injection nozzles?
Multi-hole
Pintle
Multi-hole nozzles
Are the most common, used in direct injection engines. Tip has a series of small holes that are precisely sized and angled to produce a specific spray pattern
Opening pressures for multi-hole nozzles range from?
2500 - 5000 PSI
Pencil fuel injectors
Are a multi-hole design, but the nozzle body and nozzle are one piece assembly. opening pressures range from 2500 - 4000 PSI
Where are pintle nozzles used?
Indirect injection engines with pre-combustion chambers
Pintle nozzles
Produce a hollow, cone shaped spray pattern as fuel sprays out of single hole. Pressures 1400-2500 PSI
What is nozzle dribble?
When the fuel continues to drip out of nozzle tip after injection has ended
What are the 3 major factor that effect injector nozzle operation?
Dirt, Heat, Water
What tools should be used to remove injector lines
2 flare nut wrenches
During engine operation, the governor does what?
Senses engine RPM
Reacts to RPM changes
Controls the fuel system to adjust metering as required
When there is no changes in engine load or speed the governor is in what state?
Steady state
In order to accomplish the required functions, engine governors have a?
Throttle mechanism (operator input) Speed sensing mechanism Connection between the speed sensing device and the fuel control linkage
Low idle speed
Lowest no load speed that the engine will run without operator input
High idle speed
The highest governor controlled no load speed of an engine
Rated engine speed
The maximum full load speed of the engine and is usually the speed at which engine develops is max power
Peak torque speed
Where max torque is developed
Speed droop
Is the change in engine RPM from a no load to full load condition, generally expressed as a percentage of the rated speed.
Isochronous governing
Is a condition in which a zero speed droop condition occurs as engine loads change. With a isochronous governor, the no-load speed is the same as full-load speed
What are the 3 types of mechanical governors?
Limiting speed
Variable speed
Constant speed
Where would you commonly find timing mark for positioning the engine?
The flywheel and vibration damper
What is the purpose of the retraction step?
To assist in the delivery valve(s) in creating a quick EOI, it is machined as part of the internal cam ring lobe design
The timing advance of an opposed plunger fuel pump is sensitive to changes in engine speed through change in?
transfer pressure in the injection pump
