Cummins/Onan — Fuel Pump Test
Testing & diagnosis
From a Cummins/Onan service manual — check it applies to your exact model before use.
Applies to: Cummins/Onan MDKAD, Cummins/Onan MDKAE, Cummins/Onan MDKAF
Procedure
- Disconnect fuel line at outlet of fuel pump and connect pressure gauge at pump outlet. Use gauge calibrated for 0 to 15 psi (0 to 100 kPa). Do not tee into fuel line.
- Push Start/Stop switch to START and hold several seconds until fuel pressure stabilizes. Fuel pressure should stabilize between 3.5 and 6 psi (24 and 41 kPa).
- If fuel pressure less than 3.5 psi (24 kPa), check for fuel restrictions. For three feet (0.9 meters) lift, output pressure reduced by 1.0 psi (to 2.5 psi minimum).
- Relocate pump closer to fuel tank if more than 3 feet (0.9 meters) above end of fuel pickup tube.
- If pump defective, replace with correct (same part number) Onan pump. Fuel pump is not serviceable in the field.
Tools required
- Pressure gauge 0 to 15 psi (0 to 100 kPa) Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- 3.5 to 6 psi (24 to 41 kPa)
- 2.5 psi minimum for 3 ft lift
Full service-parts list: Cummins/Onan MDKAD →, Cummins/Onan MDKAE →, Cummins/Onan MDKAF →
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.