Cummins/Onan — Fuel Pump Test (Gasoline)
Testing & diagnosis · electric fuel pump
From a Cummins/Onan service manual — check it applies to your exact model before use.
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Before you start
- Do not substitute automotive electric fuel pumps for Onan-supplied pumps.
Procedure
- Remove the fuel line from the pump outlet and install a pressure gauge.
- Press the Start switch and hold for several seconds until pressure reading is constant.
- Good pump pressure falls between 4 and 5 psi (27.5 to 34.4 kPa) and stays constant.
- If below 3-1/2 psi (17.2 kPa), replace the fuel pump.
- If pressure is zero, stop cranking, check electrical connections, and retest.
Tools required
- Pressure gauge Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Fuel pump pressure 4-5 psi (27.5-34.4 kPa)
Source: Cummins/Onan service manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.