Cummins/Onan — Valve Clearance Adjustment (4-Cylinder)
Adjustments · Valves
From a Cummins/Onan service manual covering: 12.0MDJC, 15.0MDJF, 3.0MDJA, 6.0MDJB, 7.5MDJE. Check it applies to your exact model before use.
Applies to: Cummins/Onan 3.0MDJA, Cummins/Onan MDJA, Cummins/Onan MDJC, Cummins/Onan MDJE, Cummins/Onan MDJF, Cummins/Onan MDJA engine, Cummins/Onan MDJB engine, Cummins/Onan MDJE engine, Cummins/Onan MDJC engine, Cummins/Onan MDJF engine
Procedure
- Adjust valves in firing order 1-2-4-3.
- Adjust number 1 cylinder as for 2-cylinder engine.
- Turn flywheel 180 degrees clockwise for number 2 cylinder.
- Adjust number 2 cylinder.
- Turn flywheel 180 degrees clockwise for number 4 cylinder.
- Adjust number 4 cylinder.
- Turn flywheel 180 degrees clockwise for number 3 cylinder.
- Adjust number 3 cylinder.
Tools required
- feeler gauge Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Full service-parts list: Cummins/Onan 3.0MDJA →, Cummins/Onan MDJA →, Cummins/Onan MDJC →, Cummins/Onan MDJE →, Cummins/Onan MDJF →
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.