Cummins/Onan 20W-20 — Preheating and Starting
Operation · Starting system
For the Cummins/Onan 20W-20, from the Cummins/Onan service manual.
Applies to: Cummins/Onan 20W-20, Cummins/Onan RDJF engine
Before you start
- Do not exceed the one minute preheat periods.
- Do not use ether as a cold weather starting aid.
Procedure
- Engage PREHEAT switch 30 seconds if above 55 F, 60 seconds if below 55 F.
- Engage START switch while continuing preheat.
- Hold until engine comes up to speed.
- If engine fails to start in 15-20 seconds, repeat preheat and start.
- Verify oil pressure gauge reads at least 20 psi.
Specs & values
- Preheat 30 seconds above 55 F
- Preheat 60 seconds below 55 F
- Minimum oil pressure 20 psi
Full service-parts list: Cummins/Onan 20W-20 →
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.