Cummins/Onan — Testing the Fuel Transfer Pump
Testing & diagnosis
From a Cummins/Onan service manual — check it applies to your exact model before use.
Applies to: Cummins/Onan HDZAA
Procedure
- Disconnect the fuel supply line at the engine and direct the end into a 1 gallon (4 liter) container.
- Press the Display ON button on the Operator Panel to prime fuel (five minutes).
- Press the Gen OFF button to stop priming before the container fills up.
- Replace the pump if it does not provide a steady flow of fuel after air has been bled from the system.
Tools required
- 1 gallon (4 liter) container Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Flow must be at least 0.4 pints (200 mL)/minute
Full service-parts list: Cummins/Onan HDZAA →
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.