DECOMMESSION
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FIGURE 20. DECOMPRESSION MECHANISM
Timing the pump to the engine determines the port
closing point (17 degrees BTC) PC mark on flywheel.
See Figure 21. The helix position controls port
opening and is, in
turn,
controlled by the throttle
setting.
(PORT CLOSING)
GOVERNOR
ARM
FIGURE 21. INJECTION PUMP TIMING
Repair
Most fuel system troubles are not due to a faulty
injection pump. Test the rest of thefuel system before
condemning the injection pump.
Onan discourages field repair of the injection pump
because of the exceptionally close tolerances
between parts and the specialized equipment
necessary for repair. The injection pump is an
expensive part of the unit and even
a
particle of dirt as
fine as talcum powder could score its working
surfaces. If the rest of the fuel system is in working
order and fuel delivery is abnormal, remove the pump
for replacement or repair.
Removal
Remove the pump inlet and outlet lines. Remove the
two capscrews holding the pump to the eng ine and lift
it off. Don't lose the shims. They time the injection
pump to the engine. Cap all openings in the pump and
fuel lines to keep dirt out of the fuel system.
21
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