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Home›Engines›Cummins/Onan MAJ

Cummins/Onan MAJ Engine Engine

The Cummins/Onan MAJ is an engine rated at 3600 rpm. It powers generator sets from Cummins/Onan, including the 2.5MAJ.

Also known as: Onan MAJ

3600 rpm
Rated speed

Engine specifications

Rated speed3600 rpm

Generator sets powered by this engine

1
Cummins/Onan 2.5MAJ

Troubleshooting

3

Symptoms & remedies

SymptomCauseRemedy
Low Oil PressureCheck the oil level. If low, add oil to bring level up to 1 /4 inch (6 mm) from the fill opening. Do not overfill. Inspect engine exterior for leaks and repair as necessary.The oil pressure switch grounds the ignition circuit if pressure drops below 8 to 10 psi (55 to 69 kPa), and causes genset shutdown.
High Engine TemperatureCheck condition and tightness of the sea water pump belt. Sea water flow at the hull exhaust outlet for a new pump should be about 1.8 gal/min (6.8 L/min) for 60 hertz gensets, and 1.5 gal/min (5.7 L/min) for 50 hertz gensets. Also check cooling system for freedom of contaminants, rust and sludge build-up, etc.The thermostat switch closes at engine temperatures over 200' F (93' C) and grounds the ignition circuit to cause genset shutdown.
High Exhaust TemperatureHigh exhaust manifold temperature is caused by failure of the sea water cooling system. Failure can be caused by a defective sea water pump, drive belt, plugged inlet filter, or a closed water valve.Sea water flow at the exhaust outlet should be as referenced in the High Engine Temperature text. Whenever a shutdown occurs, a thorough inspection of the complete exhaust system must be made by an experienced service person.

Fault codes and symptom→remedy steps extracted from this engine’s service/owner documentation; verify against the official manual before servicing.

Common problems

3
  • If the test lamp lights, a ground is indicated.
    Fix: Find the point where the ground occurs and repair as necessary.
  • A strong pull or vibration on a slot indicates a shorted winding.
    Fix: After testing in one position, rotate the armature slightly in the growler and repeat the test. Continue until a complete revolution of the armature has been made.
  • A grounded circuit is indicated if the test lamp glows during testing.
    Fix: Remove any foreign material, install the armature, then correct excessive run-out by striking the high side of the shaft near the ball bearing.

Compiled from service & troubleshooting documentation across every generator set that uses the Cummins/Onan MAJ.

Maintenance schedule

ItemSpecCapacityPart #Interval
Air filter— find
Oil filter— find
Oil—

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

Repair guides

1

Step-by-step procedures compiled from the Cummins/Onan service manual for this engine.

Common questions

Which generators use the Cummins/Onan MAJ engine?

The Cummins/Onan MAJ powers 1 generator set(s), including Cummins/Onan 2.5MAJ.

What is a common problem with the Cummins/Onan MAJ engine?

A commonly reported issue on generators using the Cummins/Onan MAJ is: If the test lamp lights, a ground is indicated.. Fix: Find the point where the ground occurs and repair as necessary..