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Cummins/Onan OHV 4-stroke Engine

Name: Cummins/Onan OHV 4-stroke Engine
Brand: Cummins/Onan

The Cummins/Onan OHV 4-stroke is a 0.22 L engine. It powers generator sets from Cummins/Onan, including the P4500. It holds 0.63 L (0.2 gal) of oil.

Also known as: Cummins Inc. OHV 4-stroke

0.224 L

Displacement

0.63 L

Oil capacity

On this pageSpecs Generator sets FAQ Service intervals Torque & specs Fluids Fault codes Procedures Wiring

Engine specifications

Oil capacity	0.63 L
Displacement	0.224 L

Generator sets powered by this engine

Cummins/Onan P4500

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

Common problems

NO DC OUTPUT
Cause: Tripped DC circuit breaker
Fix: Disconnect battery, reset breaker and have battery tested for shorts
NO AC OUTPUT
Cause: Tripped AC circuit breaker
Fix: Remove all loads, reset breaker, check loads for defects. Do not exceed generator set rating.
Generator set not level
Fix: Move generator set to level surface
Fouled spark plug
Fix: Remove and clean or replace spark plug
ENGINE WON'T START
Cause: Low oil level
Fix: Add oil as necessary
Engine will not start or remain running while trying to start.
Cause: 1. Inverter is out of gasoline. 2. Fuel flow is obstructed. 3. Dirty air filter 4. Low oil level shutdown switch is preventing the unit from starting. 5. Spark plug boot is not fully engaged with the spark plug tip. 6. Spark plug is faulty. 7. Dirty/plugged spark arrestor 8. Stale fuel
Fix: 1. Add gasoline to the inverter. 2. Inspect and clean fuel delivery passages. 3. Check and clean the air filter. 4. Check oil level and add oil if necessary. 5. Firmly push down on the spark plug boot to ensure the boot is fully engaged. 6. Remove and check the spark plug. Replace if faulty. 7. Check and clean the spark arrestor. 8. Drain any remaining fuel from the float bowl.
ENGINE SURGES
Cause: Dirty fuel strainer
Fix: Have the strainer cleaned
ENGINE STOPS
Cause: Low oil level
Fix: Add oil as necessary
Engine is running, but no electrical output.
Cause: 1. Reset breaker is tripped. 2. The power cord’s plug connector is not fully engaged in the inverter’s outlet. 3. Faulty or defective power cord 4. Faulty or defective electrical appliance
Fix: 1. Reset the reset breaker. 2. Verify plug connector is firmly engaged in the inverter’s outlet. 3. Replace power cord. 4. Try connecting a known good appliance to verify the inverter is producing electrical power.
ENGINE DOES NOT CRANK (ELECTRIC START)
Cause: Bad battery connection
Fix: Clean and tighten battery connections
ENGINE CRANKS SLOWLY (ELECTRIC START)
Cause: Load is connected
Fix: Disconnect load while starting
BLACK EXHAUST
Fix: Contact an Onan service center

Compiled from service & troubleshooting documentation across every generator set that uses the Cummins/Onan OHV 4-stroke.

Service intervals

Item	Action	Hours	Months	Notes
Air Filter	Check			Before every use
Cooling Features	Check			Check and clean before every use
Engine Oil	Check			First service — Before every use
Engine Oil	Change	300 hr	12 mo	First service — First month or 20 hours (also change after first 20 hours of engine break-in)
Air Cleaner	Clean	50 hr	3 mo	Every 3 months or 50 hours; service more frequently in dusty environments (footnote 2)
Air Filter	Clean	50 hr	6 mo	Every 50 hours or 6 months; more frequent in dusty conditions
Cylinder Cooling Fins	Clean	50 hr	3 mo	Every 3 months or 50 hours; service more frequently in dusty environments (footnote 2)
Air Filter	Replace	300 hr	12 mo	Every 100 hours or 6 months
Fuel filter	Replace	300 hr	12 mo	Recommend service by authorized Cummins service dealer
Spark Plug	Clean	100 hr	6 mo	Every 6 months or 100 hours
Spark arrestor	Check	100 hr	6 mo	Check/clean after 100 hours of use or every 6 months
Spark arrestor	Inspect	100 hr	6 mo	Inspect/clean spark arrestor; after 100 hours or every six months
Spark plug	Check	100 hr	6 mo	Check/clean after 100 hours of use or every 6 months
Spark plug	Inspect	100 hr	6 mo	Inspect/clean spark plug; after 100 hours or every six months
Starting Battery	Check	100 hr	6 mo	If equipped
Fuel Sediment Cup	Clean	300 hr	12 mo	Must be performed by a trained and experienced mechanic
Fuel Tank	Clean	300 hr	12 mo	Must be performed by a trained and experienced mechanic
Spark Arrestor	Clean	300 hr	12 mo	Every year or 300 hours
Spark Plug	Replace	300 hr	12 mo	Replace annually
Valve Clearance	Adjust	300 hr	12 mo	Must be performed by a trained and experienced mechanic
Valve Lash	Adjust	300 hr	12 mo	Every year or 300 hours; must be performed by a trained and experienced mechanic (authorized Onan/Cummins Onan dealer)
Fuel Line	Check		24 mo	Every 2 years (replace if necessary); footnote 3 — authorized Onan/Cummins Onan dealer
General Inspection	Inspect			First service — See General Inspections; check before first start of the day and after every 8 hours of operation

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

Service specifications

Type	Item	Value	Unit	Condition
Clearance	Big End Oil Clearance	0.024 - 0.059	mm (0.0009 - 0.0023 in)	allowable limit 0.12 mm (0.0048 in)
Clearance	Big End Side Clearance	0.25 - 0.65	mm (0.0098-0.0256 in)	allowable limit 1.0 mm (0.04 in)
Clearance	Cam Height Exhaust	31.57 - 31.97	mm (1.243 - 1.259 in)	allowable limit 31.80 mm (1.252 in)
Clearance	Cam Height Intake	31.85 - 32.25	mm (1.254 - 1.270 in)	allowable limit 31.10 mm (1.224 in)
Clearance	Camshaft O.D.	15.984	mm (0.6293 in)	allowable limit 15.92 mm (0.627 in)
Clearance	Connecting Rod Big/Large End I.D. (Crankshaft)	36.015	mm (1.4179 in)	allowable limit 36.07 mm (1.420 in)
Clearance	Connecting Rod Small End I.D. (Pin End)	20.007	mm (0.7877 in)	allowable limit 20.07 mm (0.790 in)
Clearance	Crankcase Cover Camshaft Holder I.D.	16.00	mm (0.63 in)	allowable limit 16.05 mm (0.632 in)
Clearance	Crankshaft O.D. (Connecting Rod Large End)	35.991	mm (1.417 in)	allowable limit 35.93 mm (1.4145 in)
Clearance	Cylinder Head Warpage (allowable limit)	0.10	mm (0.004 in)
Clearance	Cylinder Sleeve I.D. (factory / allowable)	82.015 mm (3.229 in) / 82.17 mm (3.235 in)	mm
Clearance	Cylinder Sleeve I.D. (factory / allowable)	88.015 mm (3.465 in) / 88.17 mm (3.4713 in)	mm
Clearance	Guide-to-Stem Clearance Exhaust	0.04 - 0.067	mm (0.0016 - 0.0026 in)	allowable limit 0.13 mm (0.005 in)
Clearance	Guide-to-Stem Clearance Intake	0.02 - 0.047	mm (0.00078 - 0.0019 in)	allowable limit 0.11 mm (0.004 in)
Clearance	Piston Pin Bore I.D.	20.002	mm (0.7875 in)	allowable limit 20.042 mm (0.7891 in)
Clearance	Piston Pin O.D.	20.007	mm (0.7877 in)	allowable limit 19.95 mm (0.785 in)
Clearance	Piston Ring End Gap (Top/Second/Oil)	0.2 - 0.4	mm (0.008-0.016 in)	allowable limit 1.0 mm (0.04 in)
Clearance	Piston Ring Side Clearance (Top/Second/Oil)	0.015 - 0.045	mm (0.0006 - 0.0018 in)	allowable limit 0.15 mm
Clearance	Piston Skirt O.D. (factory / allowable)	81.97 mm (3.227 in) / 81.85 mm (3.222 in)	mm
Clearance	Piston Skirt O.D. (factory / allowable)	87.97 mm (3.463 in) / 87.85 mm (3.459 in)	mm
Clearance	Piston-to-Cylinder Clearance	0.045-0.075	mm (0.0018-0.0295 in)	allowable limit 0.12 mm (0.005 in)
Clearance	Piston-to-Piston Pin Bore Clearance	0.004 - 0.016	mm (0.00016 - 0.0006 in)	allowable limit 0.08 mm (0.0031 in)
Clearance	Starter Motor Brush Length	7.0	mm (0.28 in)	allowable limit 3.5 mm (0.14 in)
Clearance	Starter Motor Mica Depth	1.0	mm (0.04 in)	allowable limit 0.2 mm (0.008 in)
Clearance	Valve Guide I.D. IN/EX	6.60	mm (0.260 in)	allowable limit 6.66 mm (0.262 in)
Clearance	Valve Seat Width	1.1	mm (0.04 in)	allowable limit 2.0 mm (0.08 in)
Clearance	Valve Spring Free Length	39.0	mm (1.54 in)	allowable limit 37.5 mm (1.48 in)
Clearance	Valve Stem O.D. Exhaust	6.56	mm (0.258 in)	allowable limit 6.40 mm (0.252 in)
Clearance	Valve Stem O.D. Intake	6.58	mm (0.259 in)	allowable limit 6.44 mm (0.254 in)
Gap	Ignition Coil Air Gap (at flywheel)	0.4 ±0.2	mm (0.016 ±0.008 in)
Gap	Spark Plug Gap	0.028	in. (0.7 mm)
Gap	Spark Plug Gap	0.7 - 0.8	mm (0.028 - 0.031 in)
Gap	Spark plug gap	0.024 - 0.032	in (0.60 - 0.80 mm)
Gap	Spark plug gap	0.024 – 0.032 in (0.60 – 0.80 mm)	in
Gap	Spark plug gap	0.032	in. (0.80 mm)
Injection timing	Ignition Timing (Fixed)	25	o BTDC
Other	Altitude power derate	3.5	% per 1000 ft (300 m) increase in altitude
Other	Battery electrolyte specific gravity	1.270 - 1.290
Other	Carbon Brush Length	5 - 9	mm	replace if less than 5 mm (0.20 in)
Other	Carburetor pilot screw initial opening	1-5/8	turns out
Other	Spark plug installation additional tightening	3/8 to 1/2 turn	turn	after finger tight
Other	Total Harmonic Distortion	≤ 3	%
Other	Valve Head Diameter	In = 24 mm (0.94 in), Ex = 22 mm (0.87 in)	mm
Pressure	Cylinder Compression	5.0-8.5	kg/cm (79 - 121 lbs/in)	at 600 rpm
Resistance	Charging Coil Resistance (wire terminal to ground)	7.5 - 12.5	KΩ	electric start models
Resistance	Exciter Winding (Bu / Bu) Resistance	2.452 - 3.052	Ω
Resistance	Exciter Winding (Bu / Bu) Resistance	2.635 - 3.035	Ω
Resistance	Field Winding Resistance (slip rings)	41 - 51	Ω
Resistance	Field Winding Resistance (slip rings)	44 - 54	Ω
Resistance	Ignition Coil Primary Coil Resistance	0.8 - 1.0	Ω
Resistance	Ignition Coil Secondary Coil Resistance	5.9 - 7.1	KΩ	spark plug cap removed
Resistance	Main Winding (DC) (G / G) Resistance	0.143 - 0.18	Ω
Resistance	Main Winding (DC) (G / G) Resistance	0.153 - 0.193	Ω
Resistance	Main Winding I (Br / W) Resistance	0.158 - 0.194	Ω
Resistance	Main Winding I (Br / W) Resistance	0.213 - 0.253	Ω
Resistance	Spark Plug Cap Resistance	5	KΩ
Resistance	Starter Motor Armature Changing Resistance (Coil)	3.5 ±0.5	Ω
Resistance	Starter Solenoid Resistance	>1	MΩ	12V battery connected between starter terminal and solenoid body
Speed	Engine Speed	3000	RPM
Speed	Engine rated RPM	3600	rpm

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

Fluid	Grade	Standard	Ambient	Capacity	Notes
Engine oil	10W30			0.63 US qt (0.60 L)	Included recommended oil for typical use; change oil type based on ambient temperature
Engine oil	SAE 10W-30			6.0 quarts	Recommended oil for typical use; temperature chart also lists 5W-30, 10W-40, 5W-30 synthetic. Printed as '6 quarts (20.3 oz)'. Do not use 2-stroke/cycle oil.
Engine oil	SAE 10W-30 (recommended for general, all-temperature use)	American Petroleum Institute (API) SG - SF/CC - CD; also API performance class SL or SJ or better		1.1 L	Engine Oil Capacity = 1.16 US quart (1.1 liters)
Engine oil	5W-30 Synthetic		-28°C to -6°C		From oil viscosity chart (ambient temperature range)
Engine oil	5W-30	API SL or SJ or better	-28°C to 10°C		-20o F to 50o F
Engine oil	10W-40	API SL or SJ or better	-18°C to 27°C		0o F to 80o F
Engine oil	10W-30	API SL or SJ or better	-12°C to 38°C		10o F to 100o F
Engine oil	15W-40	API SL or SJ or better	-12°C to 38°C		10o F to 100o F
Engine oil	SAE 30	API Class SL or SJ or better	above 0°C	1.1 L	Best when temperatures are consistently above freezing; 32°F (0°C) and higher
Engine oil	SAE 30 (single-grade)	API SL or SJ or better	above 0°C		Best when temperatures are consistently above freezing; 30o F (0 C) and higher
Fuel	Clean, fresh unleaded gasoline with an octane rating (anti-knock index) of 87 or higher			24.6 L	Fuel tank capacity 6.5 US gal (24.6 L). Do not use gasoline or additives containing methanol; avoid leaded gasoline
Fuel	Unleaded gasoline 87–93 Octane			3.4 gallons	3.4 gallons (13 liters). Up to 10% ethanol acceptable; do NOT use E15 or E85.
Fuel	Unleaded gasoline 87–93 octane (up to 10% ethanol)			3.4 Gal (12.8 L)	DO NOT use E15 or E85; do not use gas oil mix
Fuel	Unleaded gasoline, maximum 10% ethanol, 87 octane rating or higher			12.8 L	Fuel tank size 3.4 gal / 13G shown on decal as 12.8L/3.4G
Fuel	Unleaded gasoline, octane rating (anti-knock index) 87 or higher			24.6 L	Fuel tank capacity 6.5 US Gal (24.6 L). Do not use starting fluids; do not use gasoline or additives containing methanol. Leaded gasoline requires extra maintenance.

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	Action
P100	Change engine oil, clean air filter, replace fuel filter	Maintenance reminder code displayed on the data center	Info	Change engine oil, clean air filter, replace fuel filter
P25	Change engine oil	Maintenance reminder code displayed on the data center	Info	Change engine oil
P50	Clean air filter, Change engine oil	Maintenance reminder code displayed on the data center	Info	Clean air filter, change engine oil

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

Procedures

Checking and Adjusting Valve Lash adjustment

⚠ Must be done when the engine is cold.

Tools: Feeler gauge

Remove rocker arm cover and gasket; replace gasket if damaged.
Remove spark plug to ease rotation.
Rotate engine to TDC of compression stroke.
Confirm both rocker arms loose at TDC; rotate 360 degrees if not.
Insert feeler gauge between rocker arm and push rod; check clearance.
If needed, hold adjusting nut and loosen jam nut.
Turn adjusting nut to obtain correct valve lash.
Tighten jam nut to 106 in-lb (12 N.m) while holding adjusting nut.
Recheck valve lash after tightening.
Repeat for both intake and exhaust valves.
Install rocker arm cover, gasket, and spark plug.

Checking/Adjusting the Valve Clearance adjustment

⚠ Checking and adjusting valve clearance must be done when the engine is cold

Tools: Feeler gauge, Wrench

Turn the generator off and allow the engine to cool for 30 minutes; work on a cold engine.
Place the generator on a level surface in a well-ventilated area.
Remove the engine service cover.
Remove the rocker arm cover and carefully remove the gasket.
Remove the spark plug so the engine can be rotated more easily.
Pull the recoil handle to rotate the engine to top dead center (TDC).
Verify both rocker arms are loose at TDC on the compression stroke; if not, rotate the engine 360 degrees.
Insert a feeler gauge between the rocker arm and the valve stem to measure valve clearance.
If adjustment is needed, hold the rocker arm pivot and loosen the pivot adjusting nut.
Turn the rocker arm pivot to obtain the specified clearance; hold the pivot and re-tighten the nut to the specified torque.
Recheck valve clearance and perform the procedure on the other valve if needed.
Install the gasket, rocker arm cover, and spark plug.

Governor Adjustments adjustment

Remove the fuel tank.
Loosen the nut on the governor arm pinch bolt.
Move the arm until the throttle is completely open and hold it in that position.
Rotate the governor arm shaft as far as it will go in the same direction and tighten the pinch bolt.
Check that the arm and throttle move smoothly.
Reinstall the fuel tank.
Start the engine and let it warm up; adjust the limiting screw to set the idle speed.

Valve Clearance adjustment

⚠ Checking and adjusting valve clearance must be done when the engine is cold.

Tools: Feeler gauge

Remove the rocker arm cover and carefully remove the gasket; replace if torn or damaged.
Remove the spark plug so the engine can be rotated more easily.
Rotate the engine to top dead center (TDC) by pulling the recoil handle slowly.
Verify both rocker arms are loose at TDC on the compression stroke; if not, rotate the engine 360°.
Insert a feeler gauge between the rocker arm and valve stem to measure valve clearance.
If adjustment is needed, hold the rocker arm pivot and loosen the pivot adjusting nut.
Turn the rocker arm pivot to obtain the specified clearance; re-tighten the nut to the specified torque.
Perform the procedure for the other valve.
Install the gasket, rocker arm cover, and spark plug.

Valve Clearance Adjustment adjustment

⚠ Valve clearance inspection and adjustment must be performed with the engine cold.

Tools: Feeler gauge

Remove the valve cover and set the piston at top dead center of the compression stroke.
Insert a feeler gauge between the rocker arm and valve to measure valve clearance.
If adjustment is necessary, hold the rocker arm pivot and loosen the pivot lock nut.
Turn the rocker arm pivot to obtain the specified clearance.
Retighten the lock nut while holding the rocker arm pivot.
Recheck valve clearance after tightening the lock nut.

Connect the Battery installation

Push down the battery access cover tab and pull the cover forward to remove it.
Verify the rubber battery strap is firmly securing the battery; hook it onto the mounting base if loose.
Remove the cable tie securing the quick-connect battery plugs then push firmly to connect them.
Align the tabs on the battery access cover and push to reinstall.

Connecting the Battery installation

Depress the tab on the battery access cover and pull it away from the generator.
Verify that the rubber battery strap is firmly securing the battery in place.
Remove the cable tie securing the quick-connect plugs then push firmly to connect them.
Reinstall the cover.

High Altitude Kit Installation Procedure installation

⚠ This high-altitude kit is to be used at elevations above 2000 feet

⚠ DO NOT operate the generator at altitudes below 2,000 ft (762 m) with the high-altitude kit installed

Tools: Flat head screwdriver, Wrench

Remove battery access panel and disconnect the battery.
Remove the maintenance panel on the side by removing the 5 bolts that secure it.
Remove the control panel by removing the 4 face screws and the two screws on each side; let it hang loose.
Drain all the fuel from the carburetor float bowl into a suitable container.
Remove the two bolts that secure the air filter box to the carburetor; remove the lid and foam element.
Remove the clamp on the vapor tube; remove the vapor tube and crankcase breather.
Remove the two nuts that hold the box base to the carburetor and slide it off.
Remove the gasket from the carburetor front face; remove the two electrical connections from the stepper motor.
Slide the carburetor off the studs and turn it sideways to remove the fuel line.
Remove the bolt at the bottom of the float bowl and remove the float bowl.
Using a flat head screwdriver, remove the main jet; the jet and emulsion tube will fall out.
Install the emulsion tube back into the carburetor with the ridge on top going in first.
Select the appropriate jet for your altitude and install it with a flathead screwdriver.
Reinstall the float bowl gasket and the float bowl.
Reinstall the carburetor, gasket, air filter box, control panel, and side panel; start and verify operation.

Hooking Up the Battery installation

⚠ Always connect positive cable first; disconnect negative cable first.

Unclip battery access panel on back of unit.
Pull down battery strap clip and unhook from mounting base.
Lift battery, withdraw bottom-first, stand vertically.
Clip battery quick connect to main lead inside inverter.
Verify positive cable securely tightened to positive post.
Insert battery top-first through access port, stand on mounting base.
Check battery positioned correctly, cables not kinked.
Pass strap under negative cable and over battery top, hook to base.
Replace battery access cover.

Parallel Operation installation

⚠ NEVER connect or disconnect the parallel cord leads when a generator is running.

⚠ DO NOT connect two red leads or two black leads into the same generator.

Make sure both generator battery switches and ECO MODE switches are in the OFF position.
Connect the black and red parallel cable leads to the black parallel ports; black lead to left port, red lead to right port.
Connect the green ground lead to the ground terminal on each generator and tighten the nut.
Start one generator and wait until the OUTPUT READY LED illuminates.
Start the second generator and wait until the OUTPUT READY LED illuminates before connecting a load.
Connect additional loads as described in the Power Management section.
Unplug all loads before stopping the generators.

Reprogramming the Remote Start installation

Turn the generator battery switch to the ON position.
Push and hold the ON/OFF button for 10 seconds, then release; the start indicator light will flash green.
Push the ON button on the remote start key fob; it will pair automatically and the light will stop flashing.

Add Engine Oil maintenance

Tools: Funnel

Unclip and remove oil service panel to access oil fill drain plug.
Remove oil fill plug and dipstick.
Using supplied 4-cycle engine oil and funnel, slowly add oil until full.
Do not overfill; oil will drain out through fill plug if too high.

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

Voltage reconnection

Voltage	Phase	Connection	Leads	Notes
120		Voltage selector switch: 4 connects to 1, 5 connects to 2, and 6 connects to 3	4-1, 5-2, 6-3	Measure continuity with switch wires unplugged
240		Voltage selector switch: 1 connects to 7, 2 connects to 8, and 3 connects to 9	1-7, 2-8, 3-9	Measure continuity with switch wires unplugged

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 OHV 4-stroke?

The Cummins/Onan OHV 4-stroke engine has an oil capacity of 0.63 liters.

What is the displacement of the Cummins/Onan OHV 4-stroke?

The Cummins/Onan OHV 4-stroke has a displacement of 0.224 liters.

Which generators use the Cummins/Onan OHV 4-stroke engine?

The Cummins/Onan OHV 4-stroke powers 1 generator set(s), including Cummins/Onan P4500.

What is a common problem with the Cummins/Onan OHV 4-stroke engine?

A commonly reported issue on generators using the Cummins/Onan OHV 4-stroke is: NO DC OUTPUT. Cause: Tripped DC circuit breaker. Fix: Disconnect battery, reset breaker and have battery tested for shorts.