Cummins/Onan — Mechanical Fuel Pump Reconditioning
Repair & overhaul
From a Cummins/Onan service manual — check it applies to your exact model before use.
Applies to: Cummins/Onan MCCK
Before you start
- Fuel leakage is a fire and explosion hazard. All parts must align perfectly or pump will leak fuel.
Procedure
- Remove fuel lines and mounting screws holding pump to engine.
- Scribe a mark across the joint of upper and lower pump bodies; remove four assembly screws and separate bodies.
- Remove valve retainer, valves, valve springs and gasket; discard valve springs, valves and valve retainer gasket.
- Clean pump body with solvent and fine wire brush.
- Install new valve gasket, valve spring and valves; reassemble valve retainer and tighten screws.
- Press down on diaphragm to compress spring, turn bracket 90 degrees to unhook diaphragm.
- Install new fuel pump rod spring, diaphragm gasket; compress spring and turn 90 degrees to reconnect diaphragm.
- Place upper body on lower body with marks aligned; insert four screws but do not tighten.
- Push pump lever to limit of travel and hold while tightening four screws.
- Mount pump on engine with new mounting gasket and connect fuel lines.
Full service-parts list: Cummins/Onan MCCK →
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.