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Cummins/Onan Onan Diesel 4-cyl Engine Engine

The Cummins/Onan Onan Diesel 4-cyl is a 1.97 L 4-cylinder natural engine rated at 1800 rpm. It powers generator sets from Cummins/Onan, including the 12.5 RDJC and 15.0 RDJC. It holds 5.7 L (1.5 gal) of oil and 11.36 L (3.0 gal) of coolant.

Also known as: Onan Onan Diesel 4-cyl

1.966 L
Displacement
4
Cylinders
1800 rpm
Rated speed
5.7 L
Oil capacity

Engine specifications

Oil capacity5.7 L
Coolant capacity11.36 L
Displacement1.966 L
Cylinders4
AspirationNatural
Rated speed1800 rpm

Generator sets powered by this engine

2
Cummins/Onan 12.5 RDJCCummins/Onan 15.0 RDJC

Common problems

2
  • Engine fails to start.
    Fix: If engine fired, repeat above procedures, including preheat. If it still does not start after 20 seconds of cranking, wait one minute before resetting the cranking limiter and trying to start the engine.
  • Engine fails to start after 20 seconds of cranking.
    Fix: Wait one minute, to conserve battery and repeat steps 1 and 2. Absence of blue exhaust smoke during cranking indicates no fuel is being delivered.

Compiled from service & troubleshooting documentation across every generator set that uses the Cummins/Onan Onan Diesel 4-cyl.

Maintenance schedule

ItemSpecCapacityPart #Interval
Oil filterFull Flow Type— find

Pooled from every document that names this exact engine — confirm the interval and part number against your unit's serial number.

Common questions

What is the oil capacity of the Cummins/Onan Onan Diesel 4-cyl?

The Cummins/Onan Onan Diesel 4-cyl engine has an oil capacity of 5.7 liters.

What is the displacement of the Cummins/Onan Onan Diesel 4-cyl?

The Cummins/Onan Onan Diesel 4-cyl has a displacement of 1.966 liters with 4 cylinders.

Which generators use the Cummins/Onan Onan Diesel 4-cyl engine?

The Cummins/Onan Onan Diesel 4-cyl powers 2 generator set(s), including Cummins/Onan 12.5 RDJC, Cummins/Onan 15.0 RDJC.

What is a common problem with the Cummins/Onan Onan Diesel 4-cyl engine?

A commonly reported issue on generators using the Cummins/Onan Onan Diesel 4-cyl is: Engine fails to start.. Fix: If engine fired, repeat above procedures, including preheat. If it still does not start after 20 seconds of cranking, wait one minute before resetting the cranking limiter and trying to start the engine..