Cummins/Onan — Adjusting the Gas Pressure Regulator
Adjustments
From a Cummins/Onan service manual — check it applies to your exact model before use.
Browse Cummins/Onan generators & specs →
Procedure
- Use a manometer which reads up to 14 inches (355.6 mm) water column.
- Shut off gas supply. Temporarily remove the 1/8-inch pipe plug at regulator inlet for testing pressure.
- Connect manometer to read gas supply line pressure.
- Open gas supply line valve. Alternately cover and uncover the regulator outlet with your palm. Watch manometer. If regulator closes completely, manometer holds steady reading.
- If manometer reading drops slightly each time you remove your hand, regulator is leaking. Turn adjusting screw inward just enough so reading remains constant.
- Close gas supply line valve. Remove manometer. Bleed air from gas supply line. Install test-hole plug in regulator. Open gas supply line valve.
- See that vent fitting is installed in the regulator hole.
- Secure hose between regulator outlet nipple and carburetor inlet with clamps on each end.
- Operate engine to assure quick starting results.
Tools required
- Manometer reading up to 14 inches water column Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Maximum allowable inlet pressure: 8 ounces (3.45 kPa)
- Minimum inlet pressure: 2 ounces (0.86 kPa)
- Factory adjusted shutoff: between 2 and 4 ounces (0.86 and 1.72 kPa)
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.