Cummins/Onan — Electric Fuel Pump Pressure Test
Testing & diagnosis
From a Cummins/Onan service manual covering: 2.5 MAJB-53BR, 2.5 MAJB-53CR, 3.0 MAJB-1R. Check it applies to your exact model before use.
Applies to: Cummins/Onan MAJ, Cummins/Onan MAJB engine
Before you start
- Do not substitute automotive type electric fuel pumps
Procedure
- Remove the fuel line from the pump outlet and install a pressure gauge.
- Press the START switch and hold it for several seconds until the pressure reading is constant.
- The pressure reading should be 4-1/2 to 5 psi (31 to 34.5 kPa); if retention is good the pressure should stay constant or drop off very slowly.
Tools required
- Pressure gauge Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- 4-1/2 to 5 psi (31 to 34.5 kPa)
Full service-parts list: Cummins/Onan MAJ →
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.