Cummins/Onan — Fuel Transfer Pump Assembly
Repair & overhaul
From a Cummins/Onan service manual — check it applies to your exact model before use.
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Before you start
- The diaphragm must be flexed, or it will deliver too much fuel pressure.
- The priming lever must be in the position shown when installing the rocker arm.
Procedure
- Soak a new diaphragm in fuel before assembling.
- Insert diaphragm spring and soaked diaphragm into pump body.
- Insert link and rocker arm into body and hook it over diaphragm pull rod; drive in pin.
- Compress rocker spring and install between body and rocker arm.
- Insert valve cages, gaskets and valve cover plate.
- Assemble cover to body with notch marks lined up; install screws but do not tighten.
- Push rocker arm to full stroke and hold to flex diaphragm.
- Tighten cover screws alternately and securely, then release rocker arm.
- Install pump on engine and repeat pressure test.
Specs & values
- Fuel pressure 12-14 Amazon eBay FridayParts $33.00 psi (83-97 kPa) at 1800 rpm
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.