Cummins/Onan — Fuel Pump Pressure Test (gasoline gensets)
Testing & diagnosis
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 an automotive fuel pump for the standard pump.
Procedure
- Disconnect the fuel line at the outlet of the fuel pump.
- Connect a pressure gauge (0-15 psi recommended) at the pump outlet; do not tee into the line.
- Push the Start/Stop switch to START and hold until fuel pressure stabilizes.
- Fuel pressure should stabilize between 3.5 and 6 psi.
- Repeat the test with the vehicle engine running.
Tools required
- Fuel pressure gauge 0-15 psi Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Fuel pressure 3.5-6 psi (24-41 FridayParts $23.93 kPa)
- Fuel pressure must not exceed 6 psi (41 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.