90
The feed pump supplies the injection pump with fuel
under pressure. Fuel flows through the fuel filters be-
fore reaching the injection pump.
The pump camshaft pressing down the piston causes
the pump chamber in the feed pump to fill with fluid.
When the cam has passed its highest point and the pis-
ton spring presses back the piston, the pump discharges
the fuel. In other words, fuel pressure is determined by
the force of the spring.
The hand primer pump is used to pump up fuel when
there is no fuel in the system.
Push rod and
thrust spring
Return fuel
Nozzle needle
Inlet
Fuel
drilling
Spring lift
Outlet
Pump camshaft
Push rod
Cam lift
Inlet
The fuel filters are of the spin-on type and are connect-
ed in parallel.
The filters have a new location compared to their loca-
tion on the THD 104 engine; they are now placed under
the starter motor.
The filter element consists of a spiral-wound paper in-
sert with very large filtration area. The layers of paper
are folded so as to form pockets with openings that face
upwards. The fuel flows axially through the pockets,
and this separates dust particles, water, etc., from the
fuel.
The injectors atomize and distribute the fuel in the en-
gine combustion chamber. Injection is at very high
pressure for maximum possible effective fuel atomiza-
tion.
The push rod and thrust spring press the needle against
the nozzle. Fuel is pressed into the fuel drilling by the
injection pump and the high pressure overcomes the
force acting against the nozzle needle so that it lifts and
fuel is injected. When fuel pressure drops, the nozzle
needle goes down again to shut off the opening.
The force of the spring determines the force acting
against the nozzle needle. the thrust spring and thereby
the injector opening pressure is adjusted with the help
of shims.
Working
space
Suction
space
