MAINTENANCE OF THE M88A1 - OD1672 - LESSON 2/TASK 1
(5) Fuel Water Separator. Fuel from the engine fuel pump (7) (figure
15 on the previous page) is filtered through the fuel/water separator filter
(9) where moisture and water is trapped by the separator; the fuel is passed
through it into the fuel injector pump (18.1).
(6) Fuel Injector Pump.
The purpose of the fuel injector pump
(figure 16 on the following page) is to deliver accurately metered
quantities of fuel under high pressure to the engine fuel injector nozzles
(15) (figure 15) through which the fuel is injected into the engine
cylinders. The pump is located in the engine-"V", between the cooling fans,
and is driven at engine speed. The pump (18.1) (figure 15) is an American
Bosch Type PSB (PS indicates single plunger; B indicates that there is a 6mm
total plunger stroke and 10 to 15mm plunger diameter range).
The pump
consists of two individual 6-cylinder, single-plunger, distributor-type
injector pumps integrated into a single 12-cylinder unit by means of a
tandem arrangement.
With this arrangement, the distributor head of each
individual pump serves one particular bank of cylinders of the engine. The
governor part of the pump is of the mechanical-centrifugal, variable speed,
internal spring type; it is driven directly from the injector pump camshaft
and controls fuel delivery as a function of the engine speed. A friction
clutch is incorporated in the governor drive system, used for protection in
quick accelerations.
The pump incorporates a fuel-limiting device which momentarily prevents
excessive fuel delivery at intermediate settings.
The injector pump
delivers accurately metered quantities of fuel under extremely high pressure
to each cylinder.
Engine shutoff is accomplished by a normally open
solenoid control unit in the injector pump. The engine FUEL SHUTOFF switch
in the master control panel actuates the circuit to close the solenoid.
Closing the solenoid cuts off fuel delivery from the injector pump and stops
the engine. The engine is equipped with a manual fuel shutoff control to
stop the engine if the electric fuel shutoff should fail.
A bleeder
pressure-relief valve in the pump outlet maintains a constant fuel pressure
by allowing any accumulated air and excess fuel to return to the fuel tanks
through the engine and fuel tank fuel return lines, check valve, hose and
selector valve. Excess fuel is used to lubricate and cool the fuel
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