TM10-3950-672-24-2
Fuel System Malfunction Diagnosis
The function of the fuel system is to inject clean,
atomized fuel into the engine cylinders at a precise time
near the end of the compression stroke of each piston.
The components of the system contribute to the delivery
of fuel to the cylinders.
Lift Pump
Note: A malfunctioning lift pump can
cause low power from the engine.
The lift pump is mechanically driven by a lobe on the
camshaft. Wear on the lever or a damaged lobe can
reduce the pumping action.
A Do not operate the fuel system with a suction
restriction of more than 152mm (6 inches) Hg.
Caution: If the diaphragm ruptures,
fuel will drain from the weep hole (B)
in the housing.
Normal pressure drop across the filter is 21 kPa [3 psi],
maximum.
The pressure drop will increase as the filter removes
pump will have reduced capacity to force fuel through a
dirty filter. This can cause low engine power.
Note: Frequent filter replacement to
get full power from the engine can
indicate a worn lift pump.
The output of the pump can be measured:
Volume (within 30 seconds):
0.75 [0.70 U.S. qt.]
Pressure: 21 to 35 kPa [3 to 5 psi]
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