Cummins/Onan — Pulse Pump Test
Testing & diagnosis · Pulse fuel pump
From a Cummins/Onan service manual — check it applies to your exact model before use.
Applies to: Cummins/Onan NHC-NHCV engine
Before you start
- Spilled fuel can ignite and cause serious personal injury or death. Thoroughly clean up any spilled fuel.
Procedure
- Operate engine at idle for five minutes to fill carburetor.
- Shut engine off and remove fuel inlet line from pump.
- Connect vacuum gauge to fuel pump inlet with fuel hose and clamps.
- Start engine and idle five seconds; record vacuum.
- Move throttle to high idle; wait five seconds; record vacuum.
- Shut off engine and reconnect fuel inlet line.
- Remove fuel outlet line and connect pressure gauge.
- Start engine and record pressure at idle and high idle.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Pump inlet vacuum minimum: 2.6 inches of mercury
- Pump outlet pressure minimum: 1.7 psi
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.