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Cummins/Onan Modified Ford V-6 ESG-642 Engine

The Cummins/Onan Modified Ford V-6 ESG-642 is an engine. It powers generator sets from Cummins/Onan, including the GGFD and GGFE. It holds 6 L (1.6 gal) of oil.

Also known as: Onan Modified Ford V-6 ESG-642

Part of the Cummins/Onan ESG642 engine family — 2 variants share parts & fitment.

6.0 L

Oil capacity

On this pageSpecs Generator sets Maintenance FAQ Torque & specs Fault codes Procedures

Engine specifications

Oil capacity	6.0 L

Generator sets powered by this engine

Cummins/Onan GGFDCummins/Onan GGFE

How to read your Cummins/Onan engine serial & model number →

Common problems

The engine does not crank in Run mode
Cause: The Emergency Stop switch has been used. (The switch button is lit.)
Fix: Pull the Emergency Switch button. To reset the engine control, push the Run-Stop-Remote switch to Stop and the Reset switch to Reset. Then push the Run-Stop-Remote switch to Run to start the genset.
The engine cranks but does not start
Cause: The engine is not getting fuel.
Fix: Open any closed fuel shutoff valve. (Valves closed for maintenance or new installations may require several crank cycles to get fuel to genset); Fill the propane supply tank; For natural gas fueled sets, check with the gas utility; Check fuel pressure at regulator (refer to Fuel Pressure in Section 6.) (High fuel pressure will prevent solenoid from opening); Check fuel solenoid (VDC present at K1+ lead during cranking); Duel Fuel Sets Only: Check relay K99. Refer to wiring diagrams in Section 7; Check pressure switch wiring. Propane − normally closed connected to common. Natural gas − normally open connected to common; Check pressure switch function (@ 3.5 inch H2O or less, should switch from natural gas to LPG); Check S14 vacuum switch (optional) for proper operation.
No output voltage
Cause: The line circuit breaker is OFF.
Fix: Find out why the circuit breaker was turned OFF, make sure it is safe to reconnect power, and then throw the circuit breaker ON.
The engine lacks power or is unstable
Cause: Current ambient conditions cause a derate, limiting power to less than rated power.
Fix: Determine proper derates for ambient conditions. Refer to specification sheet for site derating factors.
The field circuit breaker keeps tripping
Cause: The rotating rectifier assembly (diodes CR1 through CR6) is faulty
Fix: Shut down the set and check each diode according to Section 7; Service as necessary
The engine does not crank in Remote mode
Cause: The Run-Stop-Remote switch is at Stop. (The Switch-Off light will be flashing.)
Fix: Push the Run-Stop-Remote switch to Remote.
Output voltage is too high or too low
Cause: Engine speed is unstable
Fix: Troubleshoot according to the chart, The Engine Lacks Power or is Unstable
The phase currents are unbalanced
Cause: The connected loads are distributed unevenly among the phases
Fix: Shut down the set and redistribute the loads as evenly as possible
Output voltage is unstable
Cause: The voltage has been adjusted improperly
Fix: Adjust output voltage according to Section 2, AC Control
The FAULT 1 or FAULT 2 fault lamp lights. Engine shuts down immediately, engine runs for several seconds and then shuts down, or engine continues to run. FAULT 1
Cause: The standard undesignated fault functions are programmed to shut down the set when a fault is sensed. Fault 1 is time delayed while Fault 2 is immediate. The nature of the fault is an optional selection that is determined when the set installation is designed. The undesignated fault functions may also be programmed for non-shutdown or non-time delay.
There is no remote circuit signal (12 VDC at auxiliary relay board A28-TB1-6) because fuse F3 on the ECM has blown. a
Fix: A. Replace the fuse with one of the same type and amp rating (15 A).<br>b. If fuse F3 blows again, find and repair the fault in the remote control circuit, such as a loose wire that may be shorting to ground or a shorted relay coil or other component. See Section 7 for remote connections.
There is no remote circuit signal (12 VDC at auxiliary relay board A28-TB1-6) because fuse F3 on the ECM has blown F3
Cause: Fuse F3 on the ECM has blown.
Fix: Replace the fuse with one of the same type and amp rating (15 A); If fuse F3 blows again, find and repair the fault in the remote control circuit, such as a loose wire that may be shorting to ground or a shorted relay coil or other component. See Section 7 for remote connections.
The OVERSPEED lamp comes on and the engine shuts down within 1 to 5 seconds (no overspeed condition detected). (V6 Spec A & B, V10 Spec A−C)
Fix: Remove K5-30 lead from K5. Start genset. If set shuts down and overspeed light is on, replace ECM (A11); Remove K5-30 lead from K5 and check lead continuity to ground. If ground present, replace ignition module; Connect K5-30. Remove lead K5-87 and check lead continuity to ground. If ground present, replace K5 relay; Remove K5-87 lead from K5 and start genset. If set shuts down and OVERSPEED lamp comes on, replace ECM (A11); Check Ford engine harness oil pressure lead for proper ground to intake manifold. Must be grounded to prevent false ignition module fault.
The OVERSPEED lamp comes on and the engine shuts down after 1 or more minutes (no overspeed condition detected).
Cause: Low coolant; Air in cooling system; Defective engine cylinder switch.
Fix: Fill cooling system; Bleed cooling system; Remove plug from engine cylinder switch. Start genset. If no fault, switch is defective. (This switch is not used by the control, but can cause fault condition if defective.)
The magnetic speed pick-up is defective or requires adjustment. 9
Fix: Refer to Magnetic Speed Pickup Unit Adjustment in Section 6.

Compiled from service & troubleshooting documentation across every generator set that uses the Cummins/Onan Modified Ford V-6 ESG-642.

Maintenance schedule

Item	Spec	Part #	Interval
Air filter		—	8 hr
Fuel filter		—	100 hr
Oil filter		—	2000 hr
Battery	Ignition of explosive battery gases can cause severe personal injury or death. Arcing at battery terminals, light switch or other equipment, flame, pilot lights and sparks can ignite battery gas. Do not smoke, or switch trouble light ON or OFF near battery. Discharge static electricity from body before touching batteries by first touching a grounded metal surface.	—	200 hr
Belt		—	100 hr
Coolant		—
Coolant filter	Check radiator hoses for wear and cracks	—	100 hr
Oil		—	8 hr
Spark plug		—	1000 hr

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

Service specifications

Type	Item	Value	Unit	Condition
Other	Low Fuel warning (yellow lamp)	5	inches (127 mm) WC or less	dual or single fuel systems
Other	Overcrank timed cranking period	approximately 75	seconds, including two rest periods
Other	Secondary regulator initial adjustment (distance from top of regulator to top of set screw), NG, 60 Hz	12.1	mm
Other	Secondary regulator initial adjustment, NG, 60 Hz	13.35	mm
Other	Secondary regulator initial adjustment, NG, 60 Hz	15.9	mm
Pressure	LOP jumper alternate shutdown setting	14	psi (97 kPa)	alternate jumper position (not recommended, see caution)
Pressure	LPG gas pressure at mixer, full load	approximately -1.0	inches WC
Pressure	LPG gas pressure at mixer, no load	approximately -0.5	inches WC
Pressure	Low Oil Pressure shutdown (red lamp), LOP jumper set to 25 psi	less than 25	psi (173 kPa)
Pressure	NG gas pressure at mixer, full load	approximately 5	inches WC
Pressure	Natural gas fuel supply pressure, maximum	13.6	inches WC (3.4 kPa)
Pressure	Natural gas fuel supply pressure, minimum	7	inches WC (1.7 kPa)
Pressure	Normal engine oil pressure	40-65	psi (276-449 kPa)	at normal operating temperature
Pressure	Pre-LOP warning point (14 psi jumper setting)	20	psi (138 kPa)
Pressure	Pre-LOP warning point (25 psi jumper setting)	30	psi (207 kPa)
Pressure	Pre-Low Oil Pressure warning (yellow lamp)	less than 30	psi (207 kPa)
Resistance	Magnetic speed pickup unit (MPU) resistance	1,000-1,050	ohms	replace MPU if outside range
Resistance	Stator winding insulation resistance, minimum	1	megohm	replace stator if less
Speed	Overspeed shutdown, Type A (naturally aspirated) sets	2250 ± 30	RPM
Speed	Overspeed shutdown, Type B (turbo) sets	2400 ± 30	RPM
Temperature	High Engine Temperature shutdown (red lamp)	greater than 230	°F (110°C)
Temperature	Low Engine Temperature warning (yellow lamp)	less than 65 (or 90 with sensor board jumper)	°F (18°C or 32°C); 70°F (21°C) without sensor board
Temperature	Normal coolant temperature	165-195	°F (74-91°C)
Temperature	Pre-High Engine Temperature warning (yellow lamp)	greater than 220	°F (104°C)
Voltage	AC output residual/build-up test voltage, PMG-excited	110 to 220	VAC	applied to exciter for one to two seconds during bench test
Voltage	MPU output voltage at cranking speed, minimum	1.5	VAC	replace MPU if less

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

Fault codes

Code	Name	Meaning	Severity
Fault 1	Fault 1 (red)	Engine shut down because of a system fault; part of a 10-second time-delay shutdown circuit (customer-wired).	Shutdown
Fault 2	Fault 2 (red)	Engine shut down because of a system fault; part of a non-time-delay shutdown circuit (customer-wired).	Shutdown
High Engine Temperature	High Engine Temperature (red)	Engine shut down due to excessively high coolant temperature (greater than 230°F / 110°C).	Shutdown
Low Engine Temperature	Low Engine Temperature (yellow)	Engine temperature less than 65°F (18°C) or 90°F (32°C); possibility engine might not start.	Warning
Low Fuel	Low Fuel (yellow, optional)	Fuel supply pressure is 5 inches (127 mm) WC or less; also indicates operation on secondary fuel supply for dual-fuel sets.	Warning
Low Oil Pressure	Low Oil Pressure (red)	Engine shut down due to excessively low oil pressure (less than 25 psi / 173 kPa).	Shutdown
Overcrank	Overcrank (red)	Engine did not start during the timed cranking period (approx. 75 seconds, including two rest periods).	Shutdown
Overspeed	Overspeed (red)	Engine shut down due to overspeed condition.	Shutdown
Pre High Engine Temperature	Pre High Engine Temperature (yellow)	Engine coolant temperature abnormally high (greater than 220°F / 104°C).	Warning
Pre Low Oil Pressure	Pre Low Oil Pressure (yellow)	Engine oil pressure abnormally low (less than 30 psi / 207 kPa).	Warning
Run	Run indicator (green)	Starter has disconnected and set is running.	Info
Switch-off	Switch-off (flashing red)	Run/Stop/Remote switch is in the Stop position, preventing remote/automatic operation.	Info

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

Procedures

Magnetic Speed Pickup Unit Adjustment adjustment

Measure MPU resistance; replace if not between 1,000 and 1,050 ohms.
With MPU removed, rotate ring gear until a tooth lines up in the center of the mounting hole.
Thread pickup in gently by hand until it just touches the ring gear tooth.
Back the pickup out 1/4 turn and set the locknut.
Verify MPU output voltage at cranking speed is at least 1.5 VAC; replace MPU if less.

Type A Gaseous Fuel Adjustment (Naturally Aspirated) adjustment

⚠ Gaseous fuels are flammable and explosive

Disconnect all loads, shut down set, and disconnect governor linkage at the carburetor.
Start engine and hold throttle closed by hand to prevent overspeed.
Adjust throttle idle position screw to obtain a frequency of 25-35 Hz.
Turn idle adjusting screw counterclockwise until engine becomes unstable, then clockwise to regain stability.
Reconnect governor linkage.
Connect full rated load and turn main fuel valve to full-rich, then lean until engine loses speed, then back to rich.
If equipped for LPG, switch to LPG and adjust LPG flow valve similarly under full load.

Verify Overspeed Fault Detection diagnostic

Tools: special tool P/N 420-0604

For Type A sets, move the throttle lever/linkage to increase RPM to the overspeed shutdown range.
For Type B sets, remove the two screws securing the throttle body cover and remove cover.
Use special tool P/N 420-0604 to turn the end of the throttle shaft.
With genset operating at no load, slowly rotate the shaft clockwise until RPM reaches the overspeed limit and shuts down.
Replace the throttle body cover after completing the test.

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 ESG642 family

Part #	Description	Category
1-800-888-6266	Phone number for Cummins Power Generation	Service part / kit
928-0142D	Operator’s Manual with PowerCommand® Control PCC2100	Service part / kit
TB1-5	Charger AC Failure	Terminal block

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 Modified Ford V-6 ESG-642?

The Cummins/Onan Modified Ford V-6 ESG-642 engine has an oil capacity of 6.0 liters.

Which generators use the Cummins/Onan Modified Ford V-6 ESG-642 engine?

The Cummins/Onan Modified Ford V-6 ESG-642 powers 2 generator set(s), including Cummins/Onan GGFD, Cummins/Onan GGFE.

How often should you change the oil in the Cummins/Onan Modified Ford V-6 ESG-642?

The Cummins/Onan Modified Ford V-6 ESG-642 oil change interval is every 8 hours.

What is a common problem with the Cummins/Onan Modified Ford V-6 ESG-642 engine?

A commonly reported issue on generators using the Cummins/Onan Modified Ford V-6 ESG-642 is: The engine does not crank in Run mode. Cause: The Emergency Stop switch has been used. (The switch button is lit.). Fix: Pull the Emergency Switch button. To reset the engine control, push the Run-Stop-Remote switch to Stop and the Reset switch to Reset. Then push the Run-Stop-Remote switch to Run to start the genset..