Cummins/Onan EC series — Specs, Engine, Parts & Maintenance

Specifications

Fuel	gasoline; natural gas or LPG
Oil capacity	6.0 L
Alternator	four pole, revolving field, voltage regulated type
Voltage options	115 V, 230 V, 115/230 V, 120/208 V, 120/240 V, 220/380 V, 127/220 V, 460 V, 575 V, 230/460 V
Phase	1 or 3
Power factor	0.8
Battery voltage	12 V
Battery quantity	1
Starting system	12 V DC
Coolant capacity	16 L

Maintenance & consumables

Item	Part #	Interval
Air filter	—	100 hr
Fuel filter	—	100 hr
Oil filter	—	200 hr
Battery	—	50 hr
Belt	—
Coolant	—	1200 hr
Coolant filter	—
Oil	—	100 hr
Spark plug	—	1500 hr

Service intervals

Item	Action	Hours	Notes
Coolant level	Check	8 hr	Daily service; check antifreeze protection in freezing weather
Crankcase oil level	Check	8 hr	Daily service; every 8 hours if operated more than 8 hours daily.
Fuel supply	Check	8 hr	Daily service; every 8 hours if operated more than 8 hours daily.
Oil level	Check	8 hr	Daily service; every 8 hours if run more than 8 hours daily
Plant cleanliness	Clean	8 hr	Daily service.
Radiator coolant level	Check	8 hr	Daily service; every 8 hours if operated more than 8 hours daily.
Battery	Check	50 hr	Electrolyte level, connections clean and tight, state of charge
Battery charge generator	Lubricate	50 hr	Two or three drops of oil in oilers at each end
Battery charging generator oilers	Lubricate	50 hr	Weekly service.
Battery connections	Inspect	50 hr	Weekly service.
Battery electrolyte level	Check	50 hr	Weekly service.
Crankcase breather	Clean	50 hr	Weekly service; every 50 hours if operated more than 50 hours weekly.
Engine oil	Change	50 hr	Maintenance schedule note: each 50 hours in freezing temperatures
Governor linkage	Lubricate	50 hr	Powdered graphite dry lubricant
Governor linkage ball joints	Lubricate	50 hr	Weekly service.
Governor oil level	Check	50 hr	Weekly service.
Air cleaner	Clean	100 hr	Under dust-free conditions every 100 hours or less frequent; more often in dust.
Air cleaner sump and filter element	Clean	100 hr	Maintenance schedule item; more often in dusty conditions
Carburetor and choke adjustment	Check	100 hr	Maintenance schedule item
Compression	Test	100 hr	Semi-monthly; approximately 150 psi plus or minus 10 per cylinder
Crankcase oil	Change	100 hr	First service — Normal temperature above 32°F.
Distributor	Lubricate	100 hr	Small amount of high temperature grease on breaker cam; few drops of oil in oiler cup
Distributor breaker points	Inspect	100 hr	Clean and inspect every 100 hours; adjust gap.
Distributor points	Inspect	100 hr	Clean and inspect; replace if burned or pitted; gap 0.024-0.026 in
Exhaust connections	Inspect	100 hr	Semi-monthly service.
Fuel pump filter bowl and screen	Clean	100 hr	Semi-monthly service.
Fuel system	Clean	100 hr	Semi-monthly; drain carburetor sediment, clean fuel pump filter bowl and screen, inspect for leaks
Fuel system sediment	Drain	100 hr	Semi-monthly service; remove carburetor drain plug.
Generator brushes and slip rings	Inspect	100 hr	Replace brushes only when worn to 1/2 inch in length
Generator commutator, slip rings, brushes	Inspect	100 hr	Semi-monthly service.
Governor adjustments	Check	100 hr	Maintenance schedule item
Lubrication points	Lubricate	100 hr	Distributor, battery charge generator, governor linkage, distributor cam
Oil filter element	Change	100 hr	Each alternate crankcase oil change; every oil change in cold or dusty conditions
Oil filter element	Replace	100 hr	Each alternate oil change normal; each oil change in cold or dusty conditions.
Oil, fuel, and cooling systems	Inspect	100 hr	Check for leaks
Spark plugs	Clean	100 hr	Semi-monthly; adjust gap per Table of Clearances
Valve tappets	Adjust	100 hr	Intake 0.019 inch, exhaust 0.019 inch, engine at operating temperature
Cooling system	Drain	1200 hr	Semi-yearly; drain and flush, refill with inhibitor or antifreeze.
Oil pan	Clean	1200 hr	Semi-yearly; remove oil pan and clean all sludge; coincide with scheduled oil change
Oil pan and inlet screen	Clean	1200 hr	Remove oil pan and clean sludge at scheduled oil change.

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	Crankshaft end play	0.004-0.008	inch
Clearance	Cylinder bore diameter - standard	3.6250-3.6274	inch
Clearance	Fan belt deflection	1/2	inch	light thumb pressure
Clearance	Generator belt deflection	1/4	inch	light thumb pressure
Clearance	Main bearing bore diameter	2.6912-2.6920	inch
Clearance	Piston to cylinder bore clearance	0.0006-0.0012	inch	at bottom of skirt
Clearance	Rocker arm to shaft clearance	0.002-0.004	inch
Clearance	Valve stem to guide clearance - intake	0.001-0.002	inch
Gap	Distributor contact point gap	0.024-0.026	inch
Gap	Spark plug gap (gaseous fuel)	0.018	inch
Gap	Spark plug gap 14 mm (gasoline fuel)	0.028-0.032	inch
Gap	Spark plug gap 18 mm (gasoline fuel)	0.028-0.032	inch
Gap	Spark plug gap gaseous fuel	0.018	inch
Gap	Spark plug gap gasoline	0.028-0.032	inch
Other	Battery specific gravity	1.225	specific gravity	full charge, ambient above 90°F
Other	Battery specific gravity	1.275	specific gravity	full charge, normal
Other	Carburetor fuel level below power-valve mounting surface	11/16 plus or minus 1/32	inch
Other	Carburetor main metering jet identification	67 for 0-5000 feet; 65 for 5000-10000 feet; 63 for 10000-15000 feet		altitude
Other	Carburetor main metering jet identification number	63		10,000-15,000 feet altitude
Other	Carburetor main metering jet identification number	65		5000-10,000 feet altitude
Other	Carburetor main metering jet identification number	67		0-5000 feet altitude
Other	Compression ratio	7.5 to 1
Other	Cooling system capacity	16	quarts
Other	Cylinder bore	3.62	inches
Other	Firing order	1-5-3-6-2-4
Other	Fuel pump volume	1 pint in 45 seconds or less		at idle speed
Other	High water temperature switch altitude adjustment	3	°F per 1000 feet above sea level	lower setting
Other	Horsepower	67.5 @1800	horsepower @ rpm
Other	Horsepower @ rpm	69 @ 1800	horsepower / rpm
Other	Oil capacity	5 (add 1 quart with filter change)	quarts
Other	Oil pump capacity	9.2	G.P.M.	4000 rpm
Other	Piston displacement	223	cubic inches
Other	Piston stroke	3.60	inches
Other	Torque	193 @1800	foot-pounds @ rpm
Other	Torque	201 @ 1800	foot-pounds @ rpm
Pressure	Brush spring tension	9 to 13	ounces
Pressure	Compression pressure	125 plus or minus 10	pounds	throttle wide open, engine at operating temperature, all spark plugs removed
Pressure	Compression pressure	150 plus or minus 10	pounds (psi)	throttle wide open, engine at operating temperature, all spark plugs removed, battery fully charged
Pressure	Engine oil pressure	40 to 60	lbs	at operating temperature
Pressure	Engine oil pressure (normal operating)	40 to 60	lbs (psi)	at operating temperature
Pressure	Fuel pump pressure	4-5	psi	900 rpm
Pressure	Fuel pump pressure	45	p.s.i.	@ 900 rpm
Pressure	Fuel pump vacuum	6	inches Hg	900 rpm
Pressure	Low oil pressure cut-off switch setting	9 to 11	lbs (psi)	switch closes below this pressure
Pressure	Oil pressure relief valve spring tension	9.76-9.84	pounds	compressed length 1.56
Resistance	Stabilizing resistor in static exciter	113	ohms	hunting condition check
Speed	50 cycle plant operating speed	1500	rpm	approximately
Speed	50 cycle speed range limits preferred	1470-1530	rpm	full load to no load within limits
Speed	60 cycle plant operating speed	1800	rpm	approximately
Speed	60 cycle speed range limits preferred	1770-1830	rpm	full load to no load within limits
Speed	Governor regulation - 50 cycle max/min speed	1590 / 1470	rpm	maximum and minimum speed limits
Speed	Governor regulation - 60 cycle max/min speed	1890 / 1770	rpm	maximum and minimum speed limits
Speed	Overspeed cut-off (centrifugal switch)	1800 to 1850	rpm	50 cycle plants
Speed	Overspeed cut-off (centrifugal switch)	2100 to 2150	rpm	60 cycle plants
Temperature	Engine water temperature	140 to 170	°F	normal operating
Temperature	High water temperature switch (nonadjustable, later models)	202 plus or minus 2	deg F
Temperature	High water temperature switch factory setting	205	°F	factory setting
Temperature	High water temperature switch setting (adjustable, earlier models)	205	deg F	factory setting; lower 3 deg F for each 1000 feet above sea level
Temperature	Thermostat fully open high temp	192	°F	high temp
Temperature	Thermostat fully open standard	179	°F	standard

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
Coolant	Clean soft (alkali free) water such as clean rain water	Use a good rust and scale inhibitor; standard antifreeze solution to protect at least 10 deg F below lowest expected temperature		16.0 US quarts	Fill radiator to within an inch or two of bottom of filler neck; remove radiator cap when draining
Coolant	clean soft (alkali-free) water	good rust and scale inhibitor; antifreeze to protect at least 10°F below lowest expected temperature		16.0 U.S. quarts	Use standard antifreeze below 32°F (0°C).
Engine oil	MS or DG type (detergent) oil, not non-detergent	MS or DG		5.0 US quarts	Add 1 quart if oil filter is changed; crankcase capacity 6 quarts dry
Engine oil	SAE 50	MS or DG heavy duty (detergent)		5.0 U.S. quarts	Above 100°F. Dry capacity 6 U.S. quarts; add 1 quart with filter change.
Engine oil	SAE 5W	MS or DG heavy duty (detergent)	below -23°C	5.0 U.S. quarts	Below -10°F (-23.3°C).
Engine oil	SAE 10	MS or DG heavy duty (detergent)	-23°C to 0°C	5.0 U.S. quarts	32°F (0°C) to -10°F (-23.3°C).
Engine oil	SAE 30	MS or DG heavy duty (detergent)	above 0°C	5.0 U.S. quarts	Above 32°F (0°C).
Fuel	Fresh, regular grade gasoline			20.0 US gallons (mounted tank on some special models)	Do not use highly leaded premium; do not use low octane 'stove gas'. Allow 1-2 inches expansion space
Fuel	Natural gas or LPG				Line pressure at regulator inlet must not exceed 5 pounds per square inch. Some LPG types do not vaporize readily at low temperatures
Fuel	fresh regular grade gasoline				Do not use highly leaded premium or low-octane stove gas. Natural gas regulator inlet pressure not to exceed 5 psi.
Grease	high temperature grease				Apply a very small amount, about the size of a match head, on distributor breaker cam surface.
Other	M 4834 A Engine Preservative Oil (SAE 10) or equivalent				For storing the plant; spray into carburetor air intake.

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

Procedures

AC Voltage Regulator Adjustment (Rotating Exciter) adjustment

⚠ Be sure engine speed is correct before attempting to correct output voltage.

Tools: dc voltmeter

Turn the manual field rheostat slightly clockwise to the RHEOSTAT ON position.
Adjust the manual rheostat to obtain an exciter voltage of 70 volts.
Shift the dc brush rig to the position giving the highest voltage.
Turn the manual field rheostat all the way counterclockwise to REGULATOR ON.
Set the regulator rheostat at approximately the middle of its rotation.
Set the adjustable sliding clip resistor to obtain the rated ac voltage.
Check that regulator range is at least 10 percent above and below rated voltage.
Regulate the ac output voltage per the voltage chart.

Distributor Point Gap Adjustment adjustment

⚠ Do not use file, sandpaper, or emery cloth on points.

Tools: feeler gauge, screwdriver

Crank engine until movable arm rubbing block rests on high point of cam.
Check gap with 0.025 inch feeler gauge.
If adjustment needed, loosen point assembly lock screws.
Insert screwdriver in adjustment slots; set gap to 0.025 inch.
Tighten lock screws; recheck gap.

Distributor Point Gap Check and Adjustment adjustment

⚠ Do not use a file, sandpaper, or emery cloth to clean or remove pits from distributor points.

Tools: feeler gauge, screwdriver

Crank the engine with the starter until the movable arm rubbing block rests on a cam high point.
Check the point gap with a 0.025 inch feeler gauge.
If adjustment is required, loosen the point assembly lock screws.
Insert the blade of a screwdriver in the adjustment slots and set a 0.025 inch gap.
Tighten the lock screws, then recheck the point gap.

Fan Belt Adjustment adjustment

Tools: wrench

Loosen fan bracket screws.
Move bracket up or down until deflection is 1/2 inch between crankshaft pulley and fan pulley.
Use light thumb pressure on belt.
Tighten bracket screws.

Fan and Generator Belt Adjustment adjustment

To adjust the fan belt, loosen the fan bracket screws.
Move the bracket up or down until 1/2 inch deflection is obtained.
To adjust the generator belt, loosen the generator link clamp screw and mounting bolts.
Move the generator until 1/4 inch deflection is obtained between generator and governor pulleys.
Check belts for cracks and wear and replace when necessary.

Generator Belt Adjustment adjustment

Tools: wrench

Loosen generator link clamp screw and two generator mounting bolts.
Move generator toward or away from engine until deflection is 1/4 inch between generator pulley and governor pulley.
Use light thumb pressure on belt.
Tighten clamp screw and mounting bolts.

Governor Adjustment adjustment

Tools: tachometer or frequency meter

With engine stopped and governor spring tensioned, adjust linkage so carburetor stop lever clears stop boss by not less than 1/32 inch.
Start plant and allow to reach operating temperature.
With no electrical load, adjust speed screw to proper no-load speed.
Apply full rated load at 0.8 power factor and check speed.
If hunting, increase slightly distance between governor main shaft and sensitivity screw.
Tighten all lock nuts.

Governor Adjustment (Includes Anti-dieseling Control) adjustment

⚠ A lean fuel mixture or a cold engine may cause hunting.

Tools: tachometer or frequency meter

With engine stopped, hold throttle wide open and tension the governor spring.
Adjust linkage length so the carburetor stop lever clears the stop pin by at least 1/32 inch.
Move the anti-diesel control set screws away from the carburetor.
Start the plant and allow it to reach operating temperature.
Adjust the speed screw for the proper no-load speed from the speed chart.
Apply a full rated load at 0.8 power factor and recheck speed.
If hunting, slightly increase distance between governor main shaft and sensitivity screw.
Tighten all lock nuts when adjustments are complete.

Ignition Timing Adjustment adjustment

⚠ Ignition timing is advanced by counterclockwise rotation of the distributor body; clockwise rotation retards timing.

Tools: timing light

Connect the timing light high tension lead to the No. 1 spark plug.
Operate the engine at idle speed and direct the timing light at the pointer.
The light should flash as the first pulley mark lines up with the pointer.
If not aligned, loosen the distributor body clamp.
Rotate the distributor body until the first mark and pointer are in line.

Regohm Voltage Regulator Dashpot Adjustment adjustment

⚠ No adjustment to any other part of the regulator plug-in unit should ever be attempted.

Remove the louvered cover from the regulator box.
Remove the clamping bar from the metal cover of the regulator plug-in unit.
Remove the cover held in place by two screws at the top.
Turn the slotted screw at the center until the hunting just stops.

Valve Tappet Adjustment adjustment

Tools: feeler gauge, wrench

Remove rocker arm covers.
Check tappet clearances with engine at operating temperature.
Adjust intake valves to 0.015 inch.
Adjust exhaust valves to 0.019 inch.
Tighten lock nut and recheck clearance.
Reinstall rocker arm covers; tighten cover nuts 2.0-2.5 foot-pounds.

Compression Test diagnostic

Tools: compression gauge

Operate engine at idle 30 minutes to warm thoroughly.
Stop engine and remove all spark plugs.
Install compression gauge in a spark plug hole.
Crank engine about four revolutions with starter.
Record gauge reading for each cylinder.
Compare readings; compression should be 125 pounds plus or minus 10 per cylinder, within 10 pounds.

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
115/230	1	3 wire	T1, T2-T3, T9	T1 and T9 are hot; T2-T3 is neutral/ground. For 115 V, hot load wires to T1 and T4 and neutral to T2-T3; two 115 V circuits. Two black wires give one 230 V circuit.
120/208	3	4 wire wye	T1, T2, T3, T0	T1, T2, T3 are hot; T0 is ground. For single-phase, hot to any T1/T2/T3 and ground to T0.
120/208	3 phase	4 wire wye	T1, T2, T3, TO	T1, T2, T3 are the hot terminals; TO is the ground terminal. Single phase (line to neutral) is 120 volts when voltmeter reads 208 volts line to line. Reverse any two terminals if motors rotate in reverse.
120/240	1	3 wire from 3-phase 4-wire delta	T1, T2, T0	T1 and T2 are hot; T0 is neutral and can be grounded. Two 120 V circuits; T1-T2 gives one 240 V circuit.
120/240	3	4 wire delta	T1, T2, T3, T0	T0 is center tap between T1 and T2; T0 is not grounded. For 240 V 3-phase 3-wire use T1, T2, T3; T0 not used.
120/240	3 phase	4 wire delta	T1, T2, T3, TO	TO is the center tap between T1 and T2 and is not grounded. 240 volt 3 phase 3 wire uses T1, T2, T3; TO is unused. Combination single phase and three phase loads may be applied if no terminal current exceeds rated current.
120/240	single phase	3 wire	T1, T2-T3, T4 (top to bottom)	T1 and T4 are the hot terminals; T2-T3 is neutral (ground). T1 to T4 gives one 240 volt circuit; T1 or T4 to T2-T3 gives two 120 volt circuits, each limited to one half rated capacity.
240	3 phase	3 wire	T1, T2, T3	None of the terminals are grounded. Three single phase circuits available using any two terminals.
3 phase	3	3 wire	T1, T2, T3	None of the terminals are grounded. For single-phase, connect to any two terminals; three single-phase circuits available.

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 fuel type does the Cummins/Onan EC series take?

The Cummins/Onan EC series runs on gasoline; natural gas or LPG.

What is the coolant capacity of the Cummins/Onan EC series?

The Cummins/Onan EC series cooling system holds 16 liters (4.2 US gallons) for the radiator system including the engine, per the manufacturer specification sheet.

What is the oil capacity of the Cummins/Onan EC series?

The Cummins/Onan EC series has an engine oil capacity of 6 liters (6.3 US quarts), per the manufacturer specification sheet.

What voltages is the Cummins/Onan EC series available in?

The Cummins/Onan EC series is offered in 115 V, 230 V, 115/230 V, 120/208 V, 120/240 V, 220/380 V, 1 or 3-phase.

What battery does the Cummins/Onan EC series use?

The Cummins/Onan EC series uses 1 battery, 12 V each, per the manufacturer specification sheet. The starting system is 12 V DC.

What alternator does the Cummins/Onan EC series use?

The Cummins/Onan EC series uses a four pole, revolving field, voltage regulated type alternator.

Troubleshooting

121

Symptoms & remedies

Symptom	Cause	Remedy
Generator overheating	Overloaded	Reduce load.
Generator overheating	Brush rig out of position	Be sure to line up marks.
Voltage drops under heavy load	Engine lacks power	See remedies for engine missing under heavy load.
Voltage drops under heavy load	Poor compression	Tighten cylinder head and spark plugs; If still not corrected, grind the valves; Replace piston rings, if necessary.
Voltage drops under heavy load	Faulty carburetion	Check the fuel system; Clean, adjust or replace parts necessary.
Voltage drops under heavy load	Restricted air cleaner	Clean and refill.
Voltage drops under heavy load	Excessive choking	See that choke opens properly.
Voltage drops under heavy load	Carbon or lead in cylinder	Remove carbon.
Voltage drops under heavy load	Restricted exhaust line	Clean or increase the size.
Engine misfires at light load	Carburetor idle adjustment set wrong or clogged	Adjust, clean if needed.
Engine misfires at light load	Spark plug gaps too narrow	Adjust to correct gap.
Engine misfires at light load	Intake air leak	Tighten or replace gaskets.
Engine misfires at light load	Faulty ignition	Clean, adjust, or replace breaker points, plugs, condenser, coil, etc., or retime ignition.
Engine misfires at light load	Uneven compression	Tighten cylinder head and spark plugs; If still not corrected, grind valves; Replace piston rings, if necessary.
Engine misfires at light load	Worn intake valve stems or guides	Replace valves or guides.
Engine misfires at heavy load	Spark plugs defective	Replace.
Engine misfires at heavy load	Faulty ignition	Clean, adjust, or replace breaker points, plugs, condensers, coil, etc., or retime ignition.
Engine misfires at heavy load	Clogged carburetor	Clean jets.
Engine misfires at heavy load	Clogged fuel screen	Clean.
Engine misfires at heavy load	Valve lash too tight	Adjust.
Engine misfires at heavy load	Defective spark plug cables	Replace.
Engine misfires at all loads	Fouled spark plug	Clean and adjust.
Engine misfires at all loads	Defective or wrong spark plug	Replace.
Engine misfires at all loads	Sticking valves	Clean stems and guides.
Engine misfires at all loads	Broken valve spring	Replace.
Engine misfires at all loads	Defective ignition wires	Replace.
Engine misfires at all loads	Defective or improperly adjusted points	Adjust or replace breaker points.
Engine misfires at all loads	Defective ignition condenser	Replace.
Engine misfires at all loads	Improper valve lash	Adjust.
Low oil pressure	Oil too light	Drain, refill with proper oil.
Low oil pressure	Oil badly diluted	Drain, refill with proper oil.
Low oil pressure	Oil too low	Add oil.
Low oil pressure	Oil relief valve not seating	Remove and clean, or replace.
Low oil pressure	Badly worn engine bearings	Replace.
Low oil pressure	Sludge on oil inlet screen	Remove and clean screen.
Low oil pressure	Badly worn oil pump	Repair or replace pump.
Low oil pressure	Defective oil pressure gauge	Replace engine or panel unit.
High oil pressure	Oil too heavy	Drain, refill with proper oil.
High oil pressure	Clogged oil passage	Clean all lines and passages.
High oil pressure	Oil relief valve stuck	Remove and clean.
High oil pressure	Defective oil pressure gauge	Replace engine or panel unit.
Plant starts but does not continue to run	START button released too soon	Hold in contact longer.
Plant starts but does not continue to run	Defective charging generator	Repair.
Plant starts but does not continue to run	Defective panel equipment	See Controls.
Engine backfires at carburetor	Lean fuel mixture	Clean or adjust carburetor.
Engine backfires at carburetor	Clogged fuel screen	Clean screen.
Engine backfires at carburetor	Intake air leak	Replace flange gaskets, tighten carburetor.
Engine backfires at carburetor	Poor fuel	Refill with good, fresh fuel.
Engine backfires at carburetor	Spark too late	Retime ignition.
Engine backfires at carburetor	Spark plug wires crossed	Install wires correctly.
Engine backfires at carburetor	Intake valves leaking	Grind or replace.
Excessive oil consumption, light blue smoky exhaust	Sludged rings, excessive bearing clearances, piston skirt collapsed, worn intake valve guides	Replace worn parts.
Excessive oil consumption, light blue smoky exhaust	Oil leaks from engine or connections (this does not cause smoky exhaust)	Replace gaskets or leaking tubing; Tighten screws and connections.
Excessive oil consumption, light blue smoky exhaust	Oil too light or diluted	Drain, refill with correct oil.
Excessive oil consumption, light blue smoky exhaust	Too large bearing clearance	Replace bearings.
Excessive oil consumption, light blue smoky exhaust	Oil pressure too high	Refer to symptoms of high oil pressure for remedies.
Excessive oil consumption, light blue smoky exhaust	Engine misfires	Refer to symptoms of engine misfires.
Excessive oil consumption, light blue smoky exhaust	Faulty ignition	Clean, adjust, or replace breaker points, plugs, condenser, coil, etc., or retime ignition.
Excessive oil consumption, light blue smoky exhaust	Unit operated at light or no load for long periods	No remedy needed.
Excessive oil consumption, light blue smoky exhaust	Too much oil	Drain excess oil.
Black, smoky exhaust, excessive fuel consumption, fouling of spark plugs with black soot, possible lack of power under heavy load	Fuel mixture too rich	Be sure all jet gaskets are in place and tight; float needle valve gasket is in place and tight; Adjust choke; Install needed carburetor parts, adjust float level.
Black, smoky exhaust, excessive fuel consumption, fouling of spark plugs with black soot, possible lack of power under heavy load	Choke not open	See that choke opens properly.
Black, smoky exhaust, excessive fuel consumption, fouling of spark plugs with black soot, possible lack of power under heavy load	Dirty carburetor air cleaner	Clean, refill to proper level.
Light pounding knock	Loose connecting rod bearing	Replace.
Light pounding knock	Low oil supply	Add oil.
Light pounding knock	Low oil pressure	Refer to symptom of low oil pressure for remedies.
Light pounding knock	Oil badly diluted	Change oil.
Engine stops unexpectedly	Fuel tank empty	Refill.
Engine stops unexpectedly	Fuel pump failure	Repair or replace.
Engine stops unexpectedly	High water temperature	See symptoms for engine overheating.
Engine stops unexpectedly	Defective ignition	Check the ignition system. Repair or replace parts necessary.
Dull metallic thud, if not bad, may disappear after few minutes operation. If bad, increases with load	Loose crankshaft	Replace bearings, unless one of the next three remedies permanently corrects the trouble.
Sharp metallic thud, especially when cold engine first started	Low oil supply	Add oil.
Sharp metallic thud, especially when cold engine first started	Low oil pressure	Refer to symptom of low pressure for remedies.
Sharp metallic thud, especially when cold engine first started	Oil badly diluted	Change oil.
Pinging sound when engine is rapidly accelerated or heavily loaded	Carbon in cylinders	Remove carbon.
Pinging sound when engine is rapidly accelerated or heavily loaded	Spark too early	Retime ignition.
Pinging sound when engine is rapidly accelerated or heavily loaded	Wrong spark plugs	Install correct plugs.
Pinging sound when engine is rapidly accelerated or heavily loaded	Spark plugs burned or carboned	Install new plugs.
Pinging sound when engine is rapidly accelerated or heavily loaded	Valves hot	Adjust tappet clearance.
Pinging sound when engine is rapidly accelerated or heavily loaded	Fuel stale or low octane	Use good fresh fuel.
Pinging sound when engine is rapidly accelerated or heavily loaded	Lean fuel mixture	Clean or adjust carburetor.
Engine cranks too stiffly	Corroded terminals	Clean and tighten terminals.
Engine cranks too stiffly	Too heavy oil in crankcase	Drain, refill with light oil.
Engine cranks too stiffly	Weak battery	Test and recharge or replace battery.
Engine cranks too stiffly	Engine stuck	Disassemble and repair.
Engine cranks too stiffly	Defective cable	Install new cable.
Engine will not start when cranked	Faulty ignition	Clean, adjust, or replace breaker points, plugs, condenser, coil, etc., or retime ignition.
Engine will not start when cranked	Lack of fuel or faulty carburetion	Refill the tank; Check the fuel system; Clean, adjust, or replace parts necessary.
Engine will not start when cranked	Clogged fuel screen	Clean.
Engine will not start when cranked	Cylinders flooded	Crank few times with spark plugs removed.
Engine will not start when cranked	Poor fuel	Drain, refill with good fuel.
Engine will not start when cranked	Poor compression	Tighten cylinder head and spark plugs; If still not corrected, grind the valves; Replace piston rings, if necessary.
Engine will not start when cranked	Wrong timing	Retime ignition.
Engine will not start when cranked	Poor choking	If plant is cold, adjust choke; If plant is warm, pull up on choke arm momentarily, while cranking.
Engine runs but current does not build up	Poor brush contact or dirty commutator or slip rings	See that brushes seat well, are free in holders, are not worn too short, and have good spring tension.
Engine runs but current does not build up	Open circuit, short circuit or ground in generator	See GENERATOR, replace part necessary.
Current unsteady but engine not misfiring	Speed too low	Adjust governor to correct speed.
Current unsteady but engine not misfiring	Poor commutator or brush contact	See that brushes seat well on commutator and slip rings, are free in holders, are not worn too short, and have good spring tension.
Current unsteady but engine not misfiring	Loose connections	Tighten connections.
Current unsteady but engine not misfiring	Fluctuating load	Correct any abnormal load condition causing trouble.
Tapping sound	Tappet clearance too great	Adjust or replace tappets.
Tapping sound	Broken valve spring	Install new spring.
Hollow clicking sound with cool engine under load	Loose pistons	If noise only slight and disappears when engine warms up, no immediate attention needed. Otherwise replace worn parts.
Voltage low at far end of line but normal near power unit	Too small line wire for load and distance	Install larger or extra wires or reduce load.
Motors run too slowly and overheat at far end of line but OK near power unit	Too small line wire for load and distance	Install larger or extra wires or reduce load.
Noisy brushes	High mica between bars of commutator	Undercut mica.
Excessive arcing of brushes	Rough commutator or rings	Turn down.
Excessive arcing of brushes	Dirty commutator or rings	Clean.
Excessive arcing of brushes	High mica	Undercut mica.
Excessive arcing of brushes	Brush rig out of position	Line up marks on brush rig and support.
Engine overheating	Low water in radiator	Refill radiator.
Engine overheating	Overloaded	Remove part of load.
Engine overheating	Improper lubrication	See low oil pressure.
Engine overheating	Radiator obstructed	Clean radiator.
Engine overheating	Ignition timing late	Adjust ignition timing.
Engine overheating	Improper ventilation	Provide for better air change.
Starter will not crank engine	Discharged battery	Test and recharge or replace battery.
Starter will not crank engine	Corroded terminals	Clean and tighten terminals.
Starter will not crank engine	Loose connections	Tighten connections.
Starter will not crank engine	Defective starter relay	Clean contacts if necessary; Replace switch if necessary.

Fault codes and symptom→remedy steps extracted from this model’s service/owner documentation; verify against the official manual before servicing.

Repair guides

Step-by-step procedures compiled from the Cummins/Onan service manual for this model.

Parts

Part #	Description	Qty	System
N/A-024	High temperature grease	1	Service part / kit	buy
N/A-035	Compression gauge	1	Service part / kit	buy
N/A-042	Manual voltage control rheostat	1	Service part / kit	buy
N/A-056	Idle adjusting needle valve	1	Service part / kit	buy
N/A-078	Main adjusting needle valve	1	Service part / kit	buy
N/A-092	Idle adjusting screw	1	Service part / kit	buy
N/A-104	Main gas adjusting screw	1	Service part / kit	buy
N/A-123	Throttle level stop screw	1	Service part / kit	buy

Service, wear & replacement parts referenced for this model and its engine — confirm the exact part for your serial number. See the full parts catalog to search and cross-reference.

Available documents

Operator's manual — 928-0003 Onan EC (spec A-E) Genset Instruction manual (Cummins/Onan)Owner's manual — 928-0003 Onan EC series Genset Instruction manual (03-1965) (Cummins/Onan)Service manual — 928-0003 Onan EC (spec A-E) Genset Instruction manual (1964) (Cummins/Onan)

This page was generated from the 3 manufacturer documents above by automated extraction; every figure shown is copied from one of them. How the data is compiled.

Cummins/Onan EC series Generator Set

Specifications

Maintenance & consumables

Service intervals

Service specifications

Recommended fluids

Procedures

Voltage reconnection

Common questions

Troubleshooting

Symptoms & remedies

Repair guides

Parts

Available documents