Cummins/Onan — Fuel Pump Pressure Test (Gasoline)
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; carburetor flooding can cause fire
Procedure
- Disconnect fuel line at pump outlet; connect pressure gauge at outlet.
- Do not tee into the fuel line (static pressure test).
- Push Start/Stop switch to START and hold until pressure stabilizes.
- Pressure should stabilize between 3.5 and 6 psi (24 and 41 kPa).
- Repeat test with vehicle engine running.
Tools required
- fuel pressure gauge 0-15 psi (0-100 kPa) Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- 3.5-6 psi (24-41 FridayParts $23.93 kPa)
- Pressure greater than 6 psi (41 kPa) is not acceptable
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.