Cummins/Onan — Electric Fuel Pump Test
Testing & diagnosis
From a Cummins/Onan service manual — check it applies to your exact model before use.
Applies to: Cummins/Onan NHC-NHCV engine
Before you start
- Gasoline is highly flammable and potentially explosive. Use extreme care; direct fuel flow into suitable container and ventilate.
Procedure
- Remove fuel line from pump outlet and install pressure gauge.
- Press START switch and hold several seconds until pressure reading is constant.
- Pressure should be 2-1/2 to 3-1/4 psi (17.2 to 22.4 kPa).
- Low pressure with little drop: check weak or broken diaphragm, spring, worn linkage, or leaky check valves.
- If pressure above maximum, check diaphragm too tight or return spring too strong.
- Repair or replace pump as needed.
Tools required
- pressure gauge Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- 2-1/2 to 3-1/4 psi (17.2 to 22.4 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.