Land Rover Diesel Distributor Pumps Bosch Bosch Manual

Fuel-injection
techniques
19Distributor plunger with stroke and delivery phases
a Inlet passage
closes.
At BDC, the metering 
slot (1) closes the inlet 
passage, and the 
distributor slot (2) opens 
the outlet port.
b Fuel delivery.
During the plunger 
stroke towards TDC 
(working stroke), 
the plunger pressurizes 
the fuel in the high-
pressure chamber (3). 
The fuel travels through 
the outlet-port passage (4) 
to the injection nozzle.
c End of delivery. 
Fuel delivery ceases 
as soon as the 
control...

During the plunger’s continued move-
ment to TDC, fuel returns through the
cutoff bore to the pump interior. During
this phase, the inlet passage is opened
again for the plunger’s next working cycle
(Fig. 10c).
During the plunger’s return stroke, its
transverse cutoff bore is closed by the
plunger’s rotating stroke movement, 
and the high-pressure chamber above the
plunger is again filled with fuel through 
the open inlet passage (Fig. 10d).
Delivery valve
The delivery valve closes off the high-
pressure...

Delivery valve with return-flow 
restriction
Precise pressure relief in the lines is 
necessary at the end of injection. This
though generates pressure waves 
which are reflected at the delivery 
valve. These cause the delivery valve 
to open again, or cause vacuum phases
in the high-pressure line. These pro-
cesses result in post-injection of fuel with
attendant increases in exhaust emis-
sions or cavitation and wear in the injec-
tion line or at the nozzle. To prevent such
harmful reflections, the...

Mechanical engine-
speed control
(governing)
Application
The driveability of a diesel-powered 
vehicle can be said to be satisfactory
when its engine immediately responds 
to driver inputs from the accelerator 
pedal. Apart from this, upon driving off
the engine must not tend to stall. The
engine must respond to accelerator-
pedal changes by accelerating or decel-
erating smoothly and without hesitation.
On the flat, or on a constant gradient,
with the accelerator pedal held in a given
position, the...

– Maximum-speed governing: With the
accelerator pedal fully depressed, the
maximum full-load speed must not
increase to more than high idle speed
(maximum speed) when the load is
removed. Here, the governor responds
by shifting the control collar back towards
the “Stop” position, and the supply of fuel
to the engine is reduced.
– Intermediate-speed governing: Vari-
able-speed governors incorporate in-
termediate-speed governing. Within 
certain limits, these governors can also
maintain the engine speeds...

Variable-speed governor
The variable-speed governor controls 
all engine speeds between start and 
high idle (maximum). The variable-speed
governor also controls the idle speed and
the maximum full-load speed, as well as
the engine-speed range in between.
Here, any engine speed can be selected
by the accelerator pedal and, depending
upon the speed droop, maintained
practically constant (Fig. 4).
This is necessary for instance when 
ancillary units (winches, fire-fighting
pumps, cranes etc.) are mounted...

start-quantity position by the ball pin on
the starting lever. This means that 
when the engine is cranked the
distributor plunger must travel through a
complete working stroke (= maximum
delivery quantity) before the cutoff bore 
is opened and delivery ceases. Thus 
the start quantity (= maximum delivery
quantity) is automatically made available
when the engine is cranked.
The adjusting lever is held in the pump
housing so that it can rotate. It can be
shifted by the fuel-delivery adjusting
screw (not...

Example (Fig. 5):
Using the accelerator pedal, the driver
sets the engine-speed control lever to a
specific position corresponding to a 
desired (higher) speed. As a result of 
this adjustment of the control-lever 
position, the governor spring is ten-
sioned by a given amount, with the 
result that the governor-spring force 
exceeds the centrifugal force of the 
flyweights and causes the start lever and
the tensioning lever to pivot around 
fulcrum M
2. Due to the mechanical 
transmission ratio designed...

Overrun (engine braking)
During downhill operation the engine is
“driven” by the vehicle, and engine
speed tends to increase. This causes
the flyweights to move outwards so that
the sliding sleeve presses against the
tensioning and start levers. Both levers
change their position and push the
control collar in the direction of less fuel 
delivery until a reduced fuel-delivery 
figure is reached which corresponds to
the new loading level. At the extreme,
the delivery figure is zero. Basically, 
with the...

Operation under load
If the driver depresses the accelerator
pedal, the engine-speed control lever 
is pivoted through a given angle. The
starting and idle springs are no longer
effective and the intermediate spring 
comes into effect. The intermediate
spring on the minimum-maximum-speed
governor provides a “soft” transition to
the uncontrolled range. If the engine-
speed control lever is pressed even 
further in the full-load direction, the 
intermediate spring is compressed until
the tensioning lever...