SERVICE MANUAL
ROBERT BOSCH MODEL MW INJECTION PUMP
Section 11
Mounting Adapter
A mounting adapter incorporating four studs attaches to
the injection pump housing. Capscrews through the
injection pump drive gear cover secure the mounting
adapter to the engine front plate. Removal of the timing
pointer plug in the adapter is necessary when verifying or
adjusting pump to engine timing.
The mounting adapter is an integral part of the injection
pump because it contains the timing pointer. During
injection pump calibration, a port closure mark is
stamped on the injection pump hub directly in line with
the pointer. Because the timing pointer is located on the
mounting adapter and the mounting adapter is fastened
to the injection pump housing by the four studs and nuts,
these four nuts should not be loosened.
Loosening the nuts and rotating the pump housing in
relationship to the mounting adapter will change the
relationship of the timing pointer/hub mark which was
established during injection pump calibration.
MW Injection Pump
Within the MW injection pump housing are the individual
barrels and plungers, roller tappets and activating
camshaft. Each barrel and plunger assembly is
connected with the control rack to allow simultaneous
changes of fuel delivery. A notch in the end of the pump
camshaft drives the tachometer adapter. Fuel is drawn
from the vehicle fuel tank through the primary and final
fuel filters by the supply pump.
Supply Pump with Hand Priming Pump
The piston-type supply pump is activated by the
eccentric on the injection pump camshaft and serves as
a mount for the hand priming pump. Since all fuel
entering the injection pump must be filtered to ensure
long pump life, the hand priming pump should be used
when changing fuel filters. Always install the fuel filters
"dry" and use the hand pump to fill the filters and bleed
air from the fuel system.
RQV and RSV Governors
A variable speed governor known as the "RQV" is used
on truck engines. RSV variable speed governors are
used
on
agricultural
and
construction
equipment
engines. RQV governors are used on truck engines
because control lever forces are much lower and do not
stress the driver’s foot.
Aneroid Assembly
Exhaust smoke levels during engine acceleration are
controlled by using an aneroid. The aneroid limits fuel
delivery during acceleration until the turbocharger speed
is sufficient to provide adequate air for complete
combustion. An external line connects the intake
manifold to the aneroid to allow manifold pressure to
activate the aneroid. A leak in the aneroid diaphragm or
intake manifold to aneroid line will cause the injection
pump to stay in the "cutback" position and reduce engine
power.
Fuel Return Valve
A fuel return check valve is mounted to the injection
pump housing and all fuel that is not injected passes
through the check valve and then through a special
orificed rubber hose. The function of the fuel return
check valve is to provide a positive seal to prevent fuel
from draining out of the pump housing when the engine
is stopped. The fuel return check valve opens at
approximately 18 psi. Therefore, total fuel flow through
the injection pump housing is controlled by the orifice in
the rubber hose as long as the supply pump pressure is
above 18 psi. After the fuel flows through the orifice, the
fuel pressure drops from the intermediate pressure
ahead of the orifice to low pressure.
CGES-185-3
PRINTED IN UNITED STATES OF AMERICA
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