Cummins/Onan — Fuel Delivery Test
Testing & diagnosis · Fuel lift pump
From a Cummins/Onan service manual — check it applies to your exact model before use.
Applies to: Cummins/Onan HDKB
Before you start
- Diesel fuel is combustible; keep flames and sparks away.
Procedure
- Disconnect fuel return hose; point end into a 1 liter container.
- Hold Start/Stop switch at STOP (Prime) for exactly one minute.
- Flow should not be less than 0.4 pints (200 ml) per minute.
- If low: replace fuel filter, check restrictions and air leaks, replace pump.
Tools required
- Quart (1 L) container Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Flow not less than 0.4 pints (200 ml) per minute
Full service-parts list: Cummins/Onan HDKB →
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.