Cummins/Onan — Fuel Flow Test
Testing & diagnosis · Fuel pump
From a Cummins/Onan service manual — check it applies to your exact model before use.
Applies to: Cummins/Onan HDKC, Cummins/Onan HDKCA, Cummins/Onan HDKCB
Before you start
- Fuel pump is not serviceable
Procedure
- Disconnect the fuel return hose and point the end into a graduated 1 liter container.
- Hold the Start/Stop switch in STOP for the duration of the test.
- Flow should not be less than 200 ml (0.4 pints) per minute.
- If low, replace the fuel filter; check for restrictions; then replace the fuel pump.
Tools required
- Graduated 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 200 ml (0.4 pints) per minute
Full service-parts list: Cummins/Onan HDKC →, Cummins/Onan HDKCA →, Cummins/Onan HDKCB →
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.