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Home›Engines›Cummins/Onan QSB5-G5NR3

Cummins/Onan QSB5-G5NR3 Engine

The Cummins/Onan QSB5-G5NR3 is a 4.5 L turbocharged and charge air cooled engine rated at 1800 rpm. It powers generator sets from Terex, including the T120. It holds 8.5 L (2.2 gal) of coolant.

Also known as: Cummins QSB5-G5NR3

Part of the Cummins/Onan QSB5 engine family — 6 variants share parts & fitment.

4.5 L
Displacement
1800 rpm
Rated speed
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Engine specifications

Coolant capacity8.5 L
Displacement4.5 L
Aspirationturbocharged and charge air cooled
Rated speed1800 rpm

Common problems

14
  • Voltage does not come up to the rated voltage
    Cause: Internal problem with the generator end
    Fix: Check for even reading across the lines, if they are not this would mean you probably have a problem with the wiring of the switch or generator. If the generator voltage reads correctly, contact the TEREX service department.
  • Uneven reading between the legs when applying 24 volts to the field wires
    Fix: Recheck your wiring connections. After you have the field wire connected start the unit again and check your output voltage. It may still be necessary to flash the fields to restore residual voltage.
  • TROUBLE LIGHT on CONTROL PANEL is illuminated
    Cause: Broken fan belt
    Fix: Inspect fan belt and replace as needed
  • No generator output voltage
    Cause: Circuit breaker tripped
    Fix: Reset circuit breaker
  • Malfunction discovered
    Fix: Identify symptoms, troubleshoot, perform repair, return to service
  • Low generator output voltage
    Cause: Voltage adjustment set too low
    Fix: Adjust voltage potentiometer
  • Low engine speed
    Fix: Call TEREX Service
  • High generator output voltage
    Cause: Voltage adjustment potentiometer set too high
    Fix: Adjust potentiometer
  • High engine speed
    Fix: Call TEREX Service
  • Fluctuating or surging generator output voltage
    Fix: Check engine fuel, oil, and air filters
  • Fluctuating generator output voltage stability
    Cause: Load may be the cause
    Fix: Redistribute load if possible
  • Engine won't crank
    Cause: Loose battery cable
    Fix: Check cables and battery electrolyte level. Recharge as necessary
  • Engine shuts down
    Cause: Oil Pressure Switch not opening automatically and TROUBLE LIGHT on
    Fix: Improper coolant use a 50/50 on
  • Engine runs, but loses power under load
    Cause: Clogged fuel system
    Fix: Check fuel system

Compiled from service & troubleshooting documentation across every generator set that uses the Cummins/Onan QSB5-G5NR3.

Parts cataloged across the Cummins/Onan QSB5 family

31
Part #DescriptionCategory
0179-3714Air Cleaner Instlair_filter
8C-3601Air Filterair_filter
PI144D1Alternator Modelalternator
UC274CAlternator Modelalternator
UC274KAlternator Modelalternator
127-0826Batterybattery
153-5720Batterybattery
8C-3620Beltbelt
8C-3600Coolant Filtercoolant_filter
8C-3627Fuel Filterfuel_filter
101-4000Gasketgasket
250-0486Oil Filteroil_filter
0100-3853-01Engine-Diesel (4ISBeG1)other_service
0179-3628Radiator Assyother_service
0179-4344Outlet Sockets Box Instlother_service
0179-4365Fuel System Instlother_service
0179-4466Circuit Breaker Assyother_service
0179-4472Heater Instlother_service
0179-4517Skid Assy (XRS)other_service
0179-4542Battery Isolator Assyother_service
0300-6029Accessory Instlother_service
0338-0000Harnessesother_service
0403-5265-02Spacer-Generator (UC274C)other_service
0403-5835-02Skidother_service
0403-5850-02Skidother_service
0403-5962End Cap-Skidother_service
0403-5966End Cap-Skid (Assy)other_service
0405-8842Enclosureother_service
3666496other_service
V2403-M-E3BGEngine Modelother_service
250-0488Spark Plugspark_plug

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 displacement of the Cummins/Onan QSB5-G5NR3?

The Cummins/Onan QSB5-G5NR3 has a displacement of 4.5 liters.

Which generators use the Cummins/Onan QSB5-G5NR3 engine?

The Cummins/Onan QSB5-G5NR3 powers 1 generator set(s), including Terex T120.

What is a common problem with the Cummins/Onan QSB5-G5NR3 engine?

A commonly reported issue on generators using the Cummins/Onan QSB5-G5NR3 is: Voltage does not come up to the rated voltage. Cause: Internal problem with the generator end. Fix: Check for even reading across the lines, if they are not this would mean you probably have a problem with the wiring of the switch or generator. If the generator voltage reads correctly, contact the TEREX service department..