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PH3300i SM, Rev. 2017-01-20
4.6.1 Fuel Pump Testing
This generator is equipped with a vacuum powered fuel pump that is mounted on a vertical frame
member behind the front cover (Fig. 25). The vacuum that powers the fuel pump comes from a
vacuum port on the insulator block between the carburetor and the engine. Before testing the fuel
pump verify that the vacuum hose from the isolator block to the fuel pump is in good condition
and has no leaks, blockages, or kinks. Replace the hose if necessary. Standard fuel line of the
same size may be used if the OEM replacement hose is unavailable.
1. Disconnect the spark plug wire so that the engine will not start while conducting this test.
2. Follow steps 1-6 in (section 5.1.1) to gain access to the fuel pump behind the front cover
(Fig. 25). Plug fuel lines as necessary.
3. Remove the fuel lines from the inlet and outlet of the fuel pump, but leave the vacuum
line attached.
4. Remove the screws that hold the fuel pump to the frame, and carefully allow the fuel
pump to hang in front of the inverter from its vacuum line.
5. Using two spare pieces of fuel line, 6-
8” long, attach one on the inlet and one on the
outlet of the fuel pump (Fig. 26).
6. Find a small open container that will safely hold a few ounces of fuel to a depth of
0.5-
1.0”. Put the fuel in it, and place it so the fuel line from the pump inlet is completely
below the surface of the fuel.
7. Hold the fuel line from the pump outlet over the edge of the container, so that any fuel
being pumped back into the container will be clearly visible.
8. Turn the ignition key to the START position and hold it there while watching the end of
the fuel line from the fuel pump outlet. Within 3-5 seconds there should be fuel flowing
back into the container in gentle pulses timed with the revolutions of the engine. This
indicates that the fuel pump is working properly.
9. If after 10 seconds of cranking there is no fuel present replace the fuel pump.
Fuel Pump
Fig. 25
Fig. 26
Fuel Pump
Inlet
Fuel Pump
Outlet
To Vacuum
Port