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

Name: Cummins/Onan Modified Ford V-6 ESG-642 Engine
Brand: Cummins/Onan

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

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

There is no remote circuit signal (12 VDC at auxiliary relay board A28-TB1-6) because the remote circuit is not functioning properly.
Fix: Apply 12 VDC to A28-TB1-6. If the engine cranks, find and repair the fault in the remote control circuit. 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. 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.
The starter disconnects normally but neither the panel nor the remote Run indicator lamps light
Cause: AC (K10) starter disconnect circuit is not working
The Run-Stop-Remote switch is at Stop. (The Switch-Off light will be flashing.)
Fix: Push the Run-Stop-Remote switch to Remote.
The magnetic speed pick-up is defective or requires adjustment. 9
Fix: Refer to Magnetic Speed Pickup Unit Adjustment in Section 6.
The grounding strap between the control box and the battery negative (−) terminal or the ground wire between the control and engine ground is loose, damaged or missing
Fix: Check for continuity (zero ohms) between the grounding stud on the bottom of the control box and the battery negative (−) terminal. If there is no continuity or the grounding strap is loose or damaged, repair as necessary.
The engine runs until fault shutdown.
Fix: 1. The OVERSPEED lamp comes on and the engine shuts down. a. Reset the ECM by pushing the Run-Stop-Remote switch to Stop and the Reset switch to Reset and restart the set, monitoring engine speed. b. Adjust the governor for Type A fuel system/check operation of Type B integrated governor (see Section 6). c. Type A: If the governor cannot be adjusted to prevent shutdown due to overspeed, check for binding in the linkage. Repair and adjust the linkage as necessary. d. Type A and B: If the set still shuts down due to overspeed, re-install the magnetic speed pick-up unit to make sure the clearance with the flywheel gear teeth is correct (see Section 6). Replace the speed-pickup unit if output voltage at cranking speed is less than 1.5 VAC. (Intermittent open on magnetic speed pick-up lead can also cause an overspeed condition.) e. Replace the governor controller board (Type A) or integrated governor assembly (Type B) if the set still shuts down due to overspeed. 2a. The OVERSPEED lamp comes on and the engine shuts down within 1 to 5 seconds (no over-speed condition detected). (V6 Spec A & B, V10 Spec A−C) a. Remove K5-30 lead from K5. Start genset. If set shuts down and overspeed light is on, replace ECM (A11). b. Remove K5-30 lead from K5 and check lead continuity to ground. If ground present, replace ignition module. c. Connect K5-30. Remove lead K5-87 and check lead continuity to ground. If ground present, replace K5 relay. d. Remove K5-87 lead from K5 and start genset. If set shuts down and OVERSPEED lamp comes on, replace ECM (A11). e. Check Ford engine harness oil pressure lead for proper ground to intake manifold. Must be grounded to prevent false ignition module fault. 2b. The OVERSPEED lamp comes on and the engine shuts down within 1 to 5 seconds (no over-speed condition detected). (V6 Spec C) f. Remove connector from J2 of the ECM (A11) board and check pin J2-6 continuity to ground. If ground present, replace ignition module. g. Check Ford engine harness oil pressure lead for proper ground to intake manifold. Must be grounded to prevent false ignition module fault.
The engine ignition system is malfunctioning. 7
Fix: Refer to wiring diagrams in Section 7. V6 Engine: a. Check for battery VDC at coil while cranking. (Red wire with green stripe.) b. Spec C − Check Ford engine harness ground lead connection. c. Spec C − Check 10 amp fuse located on Ford engine harness power block. d. Check crank position sensor (315 to 385 ohms). e. Check ignition coil (0.5 to 1.3 ohms). f. Replace ignition module if above items are OK. V10 Engine: a. Check for battery VDC at ignitor coil while cranking. (Red wire with green stripe.) b. Spec D − Check three fuses located on Ford engine harness power block. c. Spec D − Check B+ power connection of Ford engine harness power lead (starter motor stud − B1). d. Check crank position sensor (315 to 385 ohms). e. Check cam position sensor (315 to 385 ohms). f. Check ignition coil primary (0.5 to 1.3 ohms). g. Replace ignition module if above items are OK.
The engine does not crank in RUN mode
Cause: The Emergency Stop switch has been used.; A Fault Shutdown is being indicated by one of the red lights on the control panel.; Cranking voltage is too low to crank the engine.
Fix: Pull the Emergency Switch button. To reset the engine con-; Service the set as necessary. 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.; a. Clean and tighten or replace the positive (+) and negative (−) battery cable connectors and cables at the battery and the set.; b. Recharge or replace the battery. Specific gravity for a fully charged battery is approximately 1.260 at 80° F (27° C).; c. If the set is in standby service, install a battery charger.; d. Replace the engine-driven battery charging alternator if normal battery charging voltage (12 to 14 VDC) is not obtained.
The engine cranks but does not start.
Fix: 10. Incorrect main fuel valve adjustment. Refer to Gaseous Fuel Adjustment (Type A or B) in Section 6. 11. Incorrect secondary regulator adjustment. Refer to Initial Secondary Regulator Adjustment in Section 6.
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 Remote.
SWITCH OFF lamp flashes.
Fix: Indicates Run/Stop/Remote switch is in the Stop position which will prevent automatic starting if an automatic transfer switch is used. Move the Run/Stop/Remote switch to the Remote position for automatic starting.
Same as Steps 3 through 11 in the RUN mode.
Fix: See steps 3 through 11 in table Engine Does Not Crank In Run Mode.
RUN or fault lamp(s) does not light when Lamp Test switch is engaged.
Fix: Contact an authorized service center for assistance.
PRE LO OIL PRES lamp lights. Engine continues to operate. (Engine can be programmed to shut down.)
Fix: Indicates engine oil pressure has dropped to 30 psi (207 kPa). If generator is powering critical loads and cannot be shut down, wait until next shutdown period and then follow step 5 procedure. b. If engine can be stopped, follow procedures in step 5.

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.

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: There is no remote circuit signal (12 VDC at auxiliary relay board A28-TB1-6) because the remote circuit is not functioning properly.. Fix: Apply 12 VDC to A28-TB1-6. If the engine cranks, find and repair the fault in the remote control circuit. See Section 7 for remote connections..