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Home›Engines›Cummins/Onan QSJ5.9G

Cummins/Onan QSJ5.9G Engine

The Cummins/Onan QSJ5.9G is a 5.88 L 6-cylinder naturally aspirated or turbocharged (varies by generator set model) engine rated at 1800 rpm. It powers generator sets from Cummins/Onan, including the C100 N6, C45 N6, C50 N6 and C60 N6. It holds 15.1 L (4.0 gal) of oil and 16 L (4.2 gal) of coolant.

Also known as: Cummins QSJ5.9G

Part of the Cummins/Onan QSJ5.9G engine family — 4 variants share parts & fitment.

5.88 L
Displacement
6
Cylinders
1800 rpm
Rated speed
15.1 L
Oil capacity
On this pageSpecsGenerator setsMaintenanceFAQService intervalsFluidsProcedures

Engine specifications

Oil capacity15.1 L
Coolant capacity16.0 L
Displacement5.88 L
Cylinders6
AspirationNaturally aspirated or turbocharged (varies by generator set model)
Rated speed1800 rpm

Common problems

8
  • Unknown Shutdown at Idle 5134
  • Field Overload (Shutdown) 2972
  • Fault Code on Secondary Source (Information that the Fueling Has Been Shifted to Secondary Source) 5365
  • Engine Combustion (Shutdown) 5669
  • Cold Start Idle Active (Event) 6518
  • - Oil pressure sensor output out of range low Code 141
  • - Engine oil pressure low (warning) Code 143
  • - Engine coolant temperature out of range low (warning) Code 144

Compiled from service & troubleshooting documentation across every generator set that uses the Cummins/Onan QSJ5.9G.

Maintenance schedule

ItemSpecCapacityPart #Interval
Air filterReplace air cleaner.—250 hr
Fuel filterCheck fuel lines and hoses: Visually check for leaks, worn or damaged hoses. To replace, contact your authorized distributor.—24 hr
Oil filterReplace engine oil and filters. Refer to the Engine Oil section for the procedure.—250 hr
BatteryCheck battery: Check connections to verify that they are secure.—50 hr
BeltChecking drive belt condition and tension: Visually check belt for evidence of wear or slippage. To replace, contact your authorized distributor.—24 hr
CoolantReplace cooling system coolant. Check coolant sensor for damage and debris.—500 hr
OilReplace engine oil and filters. Refer to the Engine Oil section for the procedure.—250 hr
Spark plugReplace spark plugs and spark plug wires.—500 hr

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

Service intervals

3
ItemActionHoursMonthsNotes
External load bank testTest2 hrLoad generator to 100% of rated load for a period of two (2) hours; provide complete report with recommendations
Generator transfer switch testingTest6 moTesting of the generator transfer switch to be completed bi-annually on each generator
Preventative maintenanceOther6 moRequired semi-annually for: Ingersol-Rand Trailer; Kohler Trailer; Service Center - PW; South WWTP; North WWTP; Pine Street Water Well; Water Well 5 & 6

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Recommended fluids

FluidGradeStandardAmbientCapacityNotes
Coolant50/50 mixturebelow 50°CEngine coolant – 50/50 mixture; generator set cooling capability 50 oC

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Procedures

2
Preventative Maintenance Tasks (Quarterly and Semi-Annual) maintenance
  1. Replace oil, air, water, and fuel filters with new filters, if needed
  2. Check and tighten all electrical connections on generators
  3. Check and clean battery connections; check and record battery charge rates
  4. Start and load generator; while running check and record coolant temperature
  5. Check function of day tank pump
  6. Check voltage and hertz; adjust if needed
  7. Check for exhaust leaks
  8. Check fuel level
  9. Check all fluid levels
  10. Check for fluid leaks
  11. Check and tighten all belts; replace if necessary
  12. Provide report listing conditions of all systems
  13. Tighten all electrical connections in transfer switches; may require non-business hours at no additional charge
  14. Provide one (1) external load bank test to 100% of rated load for two (2) hours; provide complete report with recommendations
  15. Test the generator transfer switch bi-annually on each generator
Scheduled Maintenance Tasks (Requested) maintenance
  1. Start and run generator unloaded
  2. Check voltage and frequency; adjust if necessary
  3. Check all fluid levels
  4. Check for fluid leaks
  5. Check and adjust all belts, if necessary
  6. Oil changes based on run times/month
  7. Provide report listing conditions of all systems

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Parts cataloged across the Cummins/Onan QSJ5.9G family

4
Part #DescriptionCategory
3824510Cummins electronic cleanerService part / kit
A047A982EControls GCP E-Com USB interface cableService part / kit
A026M166accessory seal kitSeal
B180313494Onan C50N6 March InspectionService type

Parts cataloged across all variants of this engine family — verify the exact part fits your specific variant and serial number before ordering.

Common questions

What is the oil capacity of the Cummins/Onan QSJ5.9G?

The Cummins/Onan QSJ5.9G engine has an oil capacity of 15.1 liters.

What is the displacement of the Cummins/Onan QSJ5.9G?

The Cummins/Onan QSJ5.9G has a displacement of 5.88 liters with 6 cylinders.

Which generators use the Cummins/Onan QSJ5.9G engine?

The Cummins/Onan QSJ5.9G powers 6 generator set(s), including Cummins/Onan C100 N6, Cummins/Onan C45 N6, Cummins/Onan C50 N6, Cummins/Onan C60 N6, Cummins/Onan C70 N6.

How often should you change the oil in the Cummins/Onan QSJ5.9G?

The Cummins/Onan QSJ5.9G oil change interval is every 250 hours.

What is a common problem with the Cummins/Onan QSJ5.9G engine?

A commonly reported issue on generators using the Cummins/Onan QSJ5.9G is: Unknown Shutdown at Idle.