Feed Pump; Injectors; Fuel Shut-Off Valve - Volvo Penta TAMD71B Instruction Manual

9.3 Feed pump

If the injection pump is to work, it requires a sup-
ply of fuel at pressure. This is provided by the
feed pump, which is of piston type. The feed
pump is located on the injection pump and is
driven by the injection pump's camshaft.
The feed pressure is determined by an overflow
valve located on the injection pump. This valve
both limits the feed pump pressure and ensures
continuous venting of the fuel system.
The feed pump's hand pump can be used on a
stopped engine to pump fuel to the filters and in-
jection pump when venting the fuel system, for
example after replacing the fuel filters.

9.4 Injectors

The job of the injectors is to atomize and spray
the fuel, metered precisely by the injection
pump, into the engine's combustion chambers.
This injection takes place under extremely high
pressure so that atomization and combustion of
the fuel takes place as effectively as possible.
Each injector basically comprises a nozzle hold-
er and a nozzle (jet). When the fuel pressure in-
creases to a set value (opening pressure), the
nozzle needle (7), which is pressed in its seat by
the thrust spring (4), is raised, and atomized fuel
is sprayed into the engine through carefully cali-
brated holes in the nozzle body. The tension of
the thrust spring determines the opening pres-
sure of the injector.
The injectors should be checked regularly by
authorized personnel, refer to maintenance
schedule. An incorrect opening pressure or
faulty nozzle will result in smoky exhaust gases
and lower engine output.

9.5 Fuel shut-off valve

For normal stop
The engine is stopped via a solenoid valve (fuel
shut-off valve) which is activated during stop-
ping. The valve changes the direction of the fuel
flow to and from the feed pump so that a vacu-
um is created in the fuel chamber of the injection
pump. This makes it impossible for the pump el-
ement to fill up and the engine stops.
This valve is located on a bracket beneath the
injection pump.
AB Volvo Penta / Diesel Engine TAMD71B
Fig. 9.5 Feed pump
Fig. 9.6 Injectors
1. Pressure line connection
2. Connection for fuel leak-off pipe
3. Shims for setting the opening pressure
4. Thrust spring
5. Thrust pin
6. Jet
7. Nozzle needle
Fig. 9.7 Fuel shut-off valve (solenoid valve)
1. Solenoid valve
T. Inlet from fuel tank (Tank)
P. Outlet to feed pump (Pump)
F. Inlet from fuel filters (Filter)
I. Outlet to injection pump (Injection pump)
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