multi element pump Flashcards
what are the two types of CI injection pumps fitted to diesel engines?
Multielement Inline Pump
Rotary/DPA Pump
what does DPA stand for ?
Distributor Pump Application
where is the multielemnet pump usually located?
side of the engine
the multielement pump is driven by what?
the engine
there are as many _________ as there are cylinders in the multielement pump
pumping elements
each pumping element consists of what?
a plunger with a helix and a barrel with a spill and inlet port
the control rack is controlled by what?
the governor and accelerator pedal
describe the action of the control rack rotating the plunger
it rotates the plunger in the barrel and the position of the helix determines how much fuel is delivered to the injectors
describe the operation of the multielement pump
when the plunger is at bdc fuel immediately fills the space above the plunger through the inlet port. As the plunger moves upwards the helix groves allows excess fuel to spill through the spill port and into the common gallery. As the plunger moves upward it covers the inlet and spill port the trapped fuel is then pressurized and sent to the delivery valve and inturn to the injectors. The control rack can rotate plungers in the barrel to vary the amount of fuel being delivered with the helix position.
to turn off the diesel engine what device is used?
a fuel cut off device.
how does a fuel cut off device work?
when activated the control rack rotates plungers to the cut off position prevent fuel from being pressurized.
what is the main functions of the delivery valve?
- to prevent fuel from back flowing to pumping elements
- to maintain pressure in the high pressure lines
- to stop dribbling by injectors by ensuringa a rapid collapse of pressure at the end of the injectors phase
where is the delivery valve fitted
above each pumping element
what type of valve is a delivery valve
a spring loaded seat valve
pressure is further increased in a delivery valve by the………
volume reducer
when the plunger is on injection phase the rise in fuel pressure pushes the delivery valve _______ inside its guide
upwards
the action of forcing the _________ upwards in the delivery guide causes the valve to lift off its seat
unloader collar
the slight downwards movement of the delivery valve as it closes produces what in the pipeline?
small space
what pressure prevents injector dribbling by the delivery valve?
sudden pressure drop
