Cummins/Onan — Fuel Pump Test Procedure
Testing & diagnosis
From a Cummins/Onan service manual — check it applies to your exact model before use.
Applies to: Cummins/Onan NHEL
Before you start
- Do not substitute automotive fuel pump.
Procedure
- Remove fuel line from pump outlet and install pressure gauge.
- Press Start switch and hold until pressure reading is constant.
- Normal pump produces 4 to 5 psi (27.5 to 34.4 kPa).
- If pressure below 3-1/2 psi (17.2 kPa), replace fuel pump.
- If pressure is zero, check electrical connections and recheck.
Tools required
- pressure gauge Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Full service-parts list: Cummins/Onan NHEL →
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.