Cummins/Onan — Fuel pump pressure test
Testing & diagnosis
From a Cummins/Onan service manual — check it applies to your exact model before use.
Browse Cummins/Onan generators & specs →
Before you start
- Ignition of fuel might cause serious personal injury or death by fire or explosion. Do not permit any flame, cigarette, or other igniter near the fuel system.
Procedure
- Disconnect pump outlet line and install pressure gauge.
- Test valves and diaphragm by operating priming lever a few times; pressure should not drop off rapidly.
- Run engine at governed speed and measure fuel pump pressure.
- Pressure should be between 2 and 3 psi with gauge held 16 inches above fuel pump.
- If low or above maximum, overhaul or replace pump as indicated.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- 1-2 psi cranking
- 2-3 psi running with gauge 16 inches above pump
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.