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Cummins/Onan 6CTA8.3-M (JW) Engine

The Cummins/Onan 6CTA8.3-M (JW) is a 8.3 L 6-cylinder turbocharged / jacket water aftercooled engine rated at 1800 rpm, producing up to 255 kW. It powers generator sets from Cummins/Onan, including the 6CTA8.3.

Also known as: CUMMINS 6CTA8.3-M (JW)

Part of the Cummins/Onan 6CTA8.3 engine family — 11 variants share parts & fitment.

8.3 L

Displacement

Cylinders

1800 rpm

Rated speed

255 kW

Gross power

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

Engine specifications

Displacement	8.3 L
Cylinders	6
Aspiration	Turbocharged / Jacket Water Aftercooled
Rated speed	1800 rpm
Gross power	255 kW

Generator sets powered by this engine

Cummins/Onan 6CTA8.3

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

Common problems

Low power 35
Knock 338
Fuel or oil leaking from exhaust manifold 29
Exhaust smoke excessive under load 80
Excessive vibration 387
Excessive fuel consumption 86
Excessive engine moisture 38
Engine will not shut off 31

Compiled from service & troubleshooting documentation across every generator set that uses the Cummins/Onan 6CTA8.3-M (JW).

Service intervals

Item	Action	Hours	Months	Notes
Air Cleaner	Inspect	250 hr	3 mo	Every 8,000 km [5,000 mi]
Air Cleaner Service Indicator	Check	250 hr	3 mo
Air Intake System Piping	Inspect	250 hr	3 mo
Antifreeze	Check	500 hr	6 mo	Every 8,000 km [5,000 mi]
Belt Tension	Check	250 hr	3 mo	Every 8,000 km [5,000 mi]
Belt Tensioner Bearing	Inspect	250 hr	3 mo	Every 8,000 km [5,000 mi]
Charge Air Cooler	Clean	250 hr	3 mo
Coolant Filter	Replace	500 hr	6 mo	Every 8,000 km [5,000 mi]
Cooling System Condition	Check	250 hr	3 mo
Damper	Inspect	250 hr	3 mo	Every 8,000 km [5,000 mi]
Electrical Components	Inspect	250 hr	3 mo
Engine Coolant Heater	Check	250 hr	3 mo
Engine Mounting Bolts	Check	250 hr	3 mo
Fan Hub	Inspect	250 hr	3 mo	Every 8,000 km [5,000 mi]
Fuel Filter (Spin-on Type)	Change	250 hr	3 mo
Fuel Pump	Check	250 hr	3 mo
Heat Exchanger Zinc Plug	Inspect	250 hr	3 mo
Hose Condition	Check	250 hr	3 mo	Every Three Months or 250 Hours
Intake System	Inspect	250 hr	3 mo	Every 8,000 km [5,000 mi]
Lube Filter	Replace	500 hr	6 mo	Every 8,000 km [5,000 mi]
Lube Oil	Change	500 hr	6 mo	Every 8,000 km [5,000 mi]
Lubricating Oil and Filters	Change	250 hr	3 mo
Output Shafts	Lubricate	250 hr	3 mo	Lubrication of output/drive shafts
Turbocharger Mounting Nuts	Check	250 hr	3 mo
Valve Lash Clearance	Adjust	1000 hr	12 mo	Every 8,000 km [5,000 mi]
Coolant Filter	Change	500 hr	6 mo
Cooling System	Drain	500 hr	6 mo	Drain and flush cooling system; Every Six Months or 500 Hours
Fuel Filter	Replace	500 hr	6 mo	Every 16,000 km [10,000 mi]
Fuel Supply Lines	Other	500 hr	6 mo	Vent fuel supply lines
Injection Pump	Other	500 hr	6 mo	Vent injection pump
Air Compressor	Inspect	1000 hr	12 mo	Every 33,000 km [20,000 mi]
Drive Belt, Tensioner Bearing and Belt Tension	Check	1000 hr	12 mo
Overspeed Switch Operation	Check	1000 hr	12 mo	Every Year or 1000 Hours
Valve Lash	Adjust	1000 hr		After 1000 hours; contact an authorized service center for service
Antifreeze	Change	2000 hr	24 mo	Every 64,000 km [40,000 mi]; coolant mixtures with water pump lubricants and corrosion inhibitors
Coolant	Change	2000 hr	24 mo	Every 64,000 km [40,000 mi]; flush system
Engine	Clean	2000 hr	24 mo	Engine steam cleaning
Turbocharger	Inspect	2000 hr	24 mo	Every Two Years or 2000 Hours
Viscous Damper	Inspect	2000 hr	24 mo
Water Pump	Inspect	2000 hr	24 mo

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	Air compressor discharge total carbon deposit (clean if exceeded)	2	mm [1/16-inch]
Clearance	Fan hub maximum end play	0.15	mm [0.006 in]
Clearance	Thermostat fully open clearance between flow valve and flange	41.5	mm	minimum
Clearance	Turbocharger axial clearance MAX	0.093	mm
Clearance	Turbocharger axial clearance MIN	0.038	mm
Clearance	Turbocharger radial bearing clearance MAX	0.46	mm
Clearance	Turbocharger radial bearing clearance MIN	0.30	mm
Clearance	Vibration damper index line misalignment (replace if exceeded)	1.59	mm [1/16 inch]
Gap	Overspeed switch air gap	0.005 in. / 0.13 mm	in / mm
Gap	Tensioner spring case to tensioner arm clearance (replace if exceeded)	3	mm
Gap	Turbocharger wastegate actuator rod travel	0.33 to 1.27	mm	applied 200 kPa [29 psi]
Other	Drive belt maximum deflection	9.5 to 12.7	mm [3/8 to 1/2 inch]	at longest span
Other	Drive belt tension gauge value	80 to 110	lbs	using Cummins belt tension gauge ST-1293
Other	Generator voltage adjustment range via rheostat R21	+/-3 percent of rated nameplate voltage	percent
Other	LOP and HET fault time delay following starter disconnect	about 10 seconds	seconds
Other	Over/under voltage module time delay (to prevent nuisance tripping)	25 percent, or approximately 2.5 seconds	percent / seconds
Other	Overcrank limit (three 15-second cranking cycles with two 15-second rest periods)	75 seconds	seconds
Other	Overspeed module time delay	typically one second	seconds
Other	Time delayed start / time delayed stop adjustment range	1 to 15 seconds (start); 1 to 15 seconds (stop); cool-down 3-5 minutes recommended	seconds / minutes
Pressure	Idle Oil Pressure	10-30	psi	idle
Pressure	Idle Oil Pressure Shutdown Limit	8	psi	idle
Pressure	Idle Oil Pressure Warning Limit	12	psi	idle
Pressure	Low oil pressure shutdown setpoint	14 psi (97 kPa)	psi (kPa)	shutdown
Pressure	Lubricating oil pressure at low idle (minimum allowable)	69	kPa [10 psi]	low idle
Pressure	Lubricating oil pressure at rated speed (minimum allowable)	207	kPa [80 psi]	rated speed
Pressure	Lubricating oil pressure range at rated	276-414	kPa	at rated
Pressure	Max. Allowable Exhaust Back Pressure	41	in. H2O
Pressure	Max. Fuel Inlet Restriction	4	in. Hg (13.5 kPa)
Pressure	Max. Fuel Return Restriction	10	in. Hg (33.8 kPa)
Pressure	Max. Fuel Return Restriction	20	in. Hg (67.6 kPa)
Pressure	Maximum allowable exhaust back pressure	75	mm Hg [3.0 in. Hg]
Pressure	Maximum allowable fuel inlet restriction	101.6	mm-hg	low/high idle
Pressure	Maximum allowable intake restriction, dirty air filter	508	mm H2O [20.0 in. H2O]	naturally aspirated
Pressure	Maximum allowable intake restriction, dirty air filter	635	mm H2O [25.0 in. H2O]	turbocharged
Pressure	Maximum allowable restriction to pump, dirty filter	95	mm Hg [8.75 in. Hg]
Pressure	Maximum fuel drain line restriction	69	kPa	engine at rated speed and no load
Pressure	Minimum allowable pressure cap	50	kPa [7.0 psi]
Pressure	Minimum lubricating oil pressure	207	kPa	high idle rpm
Pressure	Minimum lubricating oil pressure	69	kPa	low idle (675 to 725 rpm)
Pressure	Normal Oil Pressure	40-70	psi	normal
Pressure	Oil Pressure Shutdown Limit	15	psi	normal
Pressure	Oil Pressure Warning Limit	20	psi	normal
Pressure	Pre-low oil pressure alarm setpoint	20 psi (138 kPa) or less	psi (kPa)	pre-alarm
Resistance	Circuit breaker insulation resistance (between each pole and to ground)	less than 100,000 ohms indicates a ground	ohm
Resistance	Mag pick-up (speed sensor) resistance	265	Ohms	good sensor
Resistance	Maximum resistance of starting circuit	0.002	Ohms	12V
Resistance	Maximum resistance of starting circuit	0.004	Ohms	24V
Resistance	Permanent magnet exciter stator resistance	4.4	ohms line-to-line
Resistance	Table 5-1 EXCITER ROTOR column	0.016	ohm	approximate, at 68 F (20 C) +/-10%
Resistance	Table 5-1 EXCITER ROTOR column	0.022	ohm	approximate, at 68 F (20 C) +/-10%
Resistance	Table 5-1 EXCITER ROTOR column	0.025	ohm	approximate, at 68 F (20 C) +/-10%
Resistance	Table 5-1 EXCITER ROTOR column	0.047	ohm	approximate, at 68 F (20 C) +/-10%
Resistance	Table 5-1 EXCITER ROTOR column	0.062	ohm	approximate, at 68 F (20 C) +/-10%
Resistance	Table 5-1 EXCITER ROTOR column	0.071	ohm	approximate, at 68 F (20 C) +/-10%
Resistance	Table 5-1 EXCITER ROTOR column	0.11	ohm	approximate, at 68 F (20 C) +/-10%
Resistance	Table 5-1 EXCITER STATOR column	0.67	ohm	approximate, at 68 F (20 C) +/-10%
Resistance	Table 5-1 EXCITER STATOR column	0.8	ohm	approximate, at 68 F (20 C) +/-10%
Resistance	Table 5-1 EXCITER STATOR column	1.1	ohm	approximate, at 68 F (20 C) +/-10%
Resistance	Table 5-1 EXCITER STATOR column	1.3	ohm	approximate, at 68 F (20 C) +/-10%
Resistance	Table 5-1 EXCITER STATOR column	1.7	ohm	approximate, at 68 F (20 C) +/-10%

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		Refer to Cummins engine Operation and Maintenance Manual for coolant recommendations/specifications			Balanced coolant mixture of water, antifreeze and coolant additives.
Coolant	50-percent water and 50-percent ethylene glycol-base antifreeze		above -37°C	22.2 litre	Protects the engine to -37°C [-34°F] year-around; coolant water capacity (engine side) 22.2 Litre; use Fleetguard coolant test kit CC2602 to check SCA
Coolant	50 percent water / 50 percent ethylene-glycol antifreeze	DCA4 supplemental coolant additive	above -34°C	11.4 litres [12.0 U.S. Qts] (6C8.3, 6CT8.3); 12.3 litres [13.0 U.S. Qts] (6CTA8.3)	Never exceed 70/30 antifreeze/water mix; never use 100 percent antifreeze; 50/50 mix protects to -34F (DCA4 one unit per 3.8 litres [1.00 U.S. gallon] initial charge)
Engine oil		Refer to Cummins engine Operation and Maintenance Manual for lubricating oil classification			Gensets are shipped with oil added.
Engine oil	15W-40 multiviscosity	Cummins Premium Blue or its equivalent		23.8 litre	Total system capacity 23.8 litre; no change in oil viscosity or type is needed for new or newly rebuilt engines
Engine oil	5W-20 or 5W-30 synthetic CC/CD		below -23°C		Arctic operation: for ambient temperatures consistently below -23C [-10F] with no means to keep engine warm
Engine oil	SAE 15W-40	API CE (CC/CD or CD/SF where CE unavailable); Cummins Premium Blue		22.4 litres [23.7 U.S. quarts] total including filter	Sulfated ash limit 1.0 mass percent suggested; must not exceed 1.85 mass percent
Fuel	ASTM No. 2 D diesel	ASTM No. 2 D; blends of No. 2 D and No. 1 D below 0C [32F]			Do not mix gasoline or alcohol with diesel fuel; fuel viscosity must stay above 1.3 cSt
Fuel	Diesel				Do not use zinc coated or copper fuel lines with diesel fuel.
Fuel	Number 2 Diesel	ASTM no. 2D			Use only number 2 diesel fuel; do not mix gasoline, alcohol, or gasohol with diesel fuel
Other	Starting battery electrolyte specific gravity			1.26 specific gravity	1.225 specific gravity recommended where ambient temperature is consistently above 95 F (35 C) to reduce electrolyte loss

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
121	Speed Signal Lost		Shutdown
135	Oil Pressure Sensor H		Warning
141	Oil Pressure Sensor L		Warning
143	Pre-Low Oil Pres		Warning	Indicates engine oil pressure has dropped below the warning trip point. If generator is powering critical loads and cannot be shut down, wait until next shutdown period and then follow code 415 procedure.
144	Coolant Sensor High		Warning
145	Coolant Sensor Low		Warning
146	Pre-High Coolant Temp		Warning	Indicates engine is operating near cooling system capacity. Increase in load or higher ambient temperature may cause High Coolant Temp (151) shutdown. Review 151 correction list for other possible causes.
151	High Coolant Temp		Shutdown	Allow engine to cool down completely. Check coolant level and replenish if low; look for leaks and repair. Check for obstructions to cooling airflow. Check fan belt and repair or tighten. Check blower fan and circulation pumps. Reset control and restart.
197	Low Coolant Level		Warning	Indicates engine coolant level has fallen below warning trip point. If generator is powering critical loads and cannot be shut down, wait until next shutdown period, then follow code 235 procedure. If engine can be stopped, follow code 235 procedure.
212	Oil Temp Sensor H		Warning
213	Oil Temp Sensor L		Warning
234	Overspeed		Shutdown
235	Low Coolant Level		Shutdown	Allow engine to cool down completely. Check coolant level and replenish if low; look for possible coolant leakage points and repair. Reset control and restart.
359	Fail To Start		Shutdown	Indicates possible fuel system or air induction problem. Check for empty fuel tank, fuel leaks, or plugged fuel lines. Check for dirty fuel filter and replace if necessary. Check for dirty or plugged air filter and replace if necessary. Reset control and restart.
415	Low Oil Pressure		Shutdown	Indicates engine oil pressure has dropped below shutdown trip point. Check oil level. If oil level is low, replenish. Reset control and restart.
421	Oil Temp		Warning	Indicates engine has begun to overheat. If generator is powering non-critical and critical loads and cannot be shut down: reduce load if possible; check air inlets and outlets and remove obstructions. If engine can be stopped, follow code 151 procedure and check engine oil level.
441	Low Bat Voltage		Warning	Indicates battery voltage supply to control is approaching a low level. Check battery charger fuse. Recharge or replace battery. Clean battery cable terminals and tighten all connections. Check battery charge voltage float level if applicable.
442	High Bat Voltage		Warning	Indicates battery voltage supply to control is approaching a high level. Check float level on battery charger if applicable (lower float level).
1122	Rated/Idle Trans		Info
1123	Shutdown After Battle Short		Shutdown
1124	Delayed Shutdown		Warning
1131	Battle Sh Active		Warning
1311	Customer Input #1			Nature of fault is optional customer selection. Example inputs: Low Fuel Day Tank, Water In Fuel, Ground Fault, Low Starting Hydraulic Pressure, Low Starting Air Pressure, etc. Programmable via service tool.
1312	Customer Input #2			Nature of fault is optional customer selection. Example inputs: Low Fuel Day Tank, Water In Fuel, Ground Fault, Low Starting Hydraulic Pressure, Low Starting Air Pressure, etc. Programmable via service tool.
1317	Customer Input #3			Nature of fault is optional customer selection. Example inputs: Low Fuel Day Tank, Water In Fuel, Ground Fault, Low Starting Hydraulic Pressure, Low Starting Air Pressure, etc. Programmable via service tool.
1318	Customer Input #4			Nature of fault is optional customer selection. Example inputs: Low Fuel Day Tank, Water In Fuel, Ground Fault, Low Starting Hydraulic Pressure, Low Starting Air Pressure, etc. Programmable via service tool.
1334	Crit Scaler Out Of Range		Shutdown
1335	Noncrit Scaler Out Of Range		Warning
1337	No Message		Info
1416	Fail To Shutdown		Warning
1417	Powr Down Error		Warning	Indicates controller cannot power down because of unknown condition. Possible drain on battery. Contact an authorized service center for service.
1433	Emergency Stop		Shutdown	Indicates local Emergency Stop. To reset: Pull button out; move O/Manual/Auto switch to O; press front panel Fault Acknowledge/Reset button; return switch to desired position.
1434	Remote E-Stop		Shutdown	Indicates remote Emergency Stop. See code 1433 to reset.
1435	Low Coolant Temp		Warning	Indicates engine coolant heater is not operating or is not circulating coolant. Check coolant heater power supply for blown fuse or disconnected cord; check for low coolant level and replenish; look for coolant leaks and repair.
1438	Fail To Crank		Shutdown	Indicates possible fault with control, speed sensing or starting system. See code 441 for corrective action.
1442	Weak Battery		Warning	Indicates during cranking battery voltage is at or below weak battery warning trip point for time greater than or equal to weak battery set time. See code 441 for corrective action.
1443	Battery Failed		Shutdown	Dead battery – engine will not start. See code 441 for corrective action.
1444	KW Overload		Warning
1445	Short Circuit		Shutdown
1446	High AC Voltage		Shutdown
1447	Low AC Voltage		Shutdown
1448	Under Frequency		Shutdown
1449	Over Frequency		Warning
1452	Gen CB Not Close		Warning
1453	Gen CB Not Open		Warning
1459	Reverse Power		Shutdown
1461	Loss Of Field		Shutdown
1466	Modem Failure		Warning
1468	Network Error		Warning
1469	Speed/Hz Match		Shutdown
1471	Over Current		Warning
1472	Over Current		Shutdown
2327	PTC Fault		Warning
2329	Low S1 Frequency		Warning
2331	Low S1 Voltage		Warning
2335	Excitation Fault		Shutdown
2336	Memory Error		Shutdown
2337	Pwr Tran Disabled		Warning
2338	Pwr Tran Failure		Warning
2339	Pwr Down Enabled		Warning
2341	High Control Temp		Warning
2342	Too Long In Idle (10 min.)		Warning	Indicates genset has been in Idle mode too long (10 minutes maximum).
2358	High S1 Voltage		Warning
2396	S1 CB Not Close		Warning
2397	S1 CB Not Open		Warning
2966	PTC Timeout		Warning
2967	Governor Fault		Warning
2968	AVR Fault		Warning
2969	LON Failure		Warning
2972	Field Overload		Shutdown
FAULT 1	Fault 1 (Detector-12)	Red undedicated fault; may be programmed as timed or non-timed shutdown or fault light only (normally factory set for timed shutdown)	Shutdown	Refer to Tests and Adjustments section and perform necessary adjustments
FAULT 2	Fault 2 (Detector-12)	Red fault, same features as Fault 1 (normally factory set for non-timed shutdown)	Shutdown	Refer to Tests and Adjustments section and perform necessary adjustments
HI ENG TEMP	High Engine Temperature	Red lamp; engine shutdown because coolant temperature rose above 215 F (102 C); not operable if coolant level too low	Shutdown	Maintain adequate coolant level; check coolant level and temperature gauge; replace switch S2, thermostat, or tighten fan belt as needed
LO FUEL	Low Fuel (Detector-12)	Yellow lamp; fuel supply marginally low (if equipped)	Warning	Replenish fuel supply
LO OIL PRES	Low Oil Pressure	Red lamp; engine shutdown because oil pressure dropped below 14 psi (97 kPa); fault inhibited during cranking and time delayed about 10 seconds after starter disconnect	Shutdown	Check oil level; monitor oil pressure gauge; replace switch S1 if gauge reading within normal range
LOW ENG TEMP	Low Engine Temperature (Detector-12)	Yellow lamp; engine water jacket temperature 70 F (21 C) or lower; indicates possible inoperative coolant heater	Warning	Check coolant heater; lamp should extinguish after engine warms up
OVERCRANK	Overcrank	Red lamp; starter locked out because of excessive cranking time; limits cranking to 75 seconds (three 15-second cranking cycles with two 15-second rest periods)	Shutdown	Press Reset switch (S11) to clear the fault before attempting to restart
OVERSPEED	Overspeed	Red lamp; engine shutdown due to excessive speed; factory set approximately 2100 r/min (60 Hz units) or 1850 r/min (50 Hz units)	Shutdown	Adjust or replace overspeed switch/module; reset before restarting
PRE Hi ENG TEMP	Pre-High Engine Temperature (Detector-7)	Yellow lamp; engine temperature marginally high, 205 F (97 C) or higher	Warning	Find and correct cause as soon as possible
PRE HI OIL TEMP	Pre-High Oil Temperature (Detector-12)	Yellow lamp; engine temperature marginally high	Warning

Showing the first 80 of 83 codes.

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

Procedures

Adjust Valve Lash Clearance adjustment

⚠ Be sure to disengage the engine timing pin after locating top dead center to prevent damage to the engine timing pin.

Tools: Engine barring gear, Feeler gauge

Remove the air crossover tube, support clamps, hose clamp, and wastegate sensing line.
Remove the crankcase vent tube and remove the valve cover.
Locate top dead center for cylinder No. 1 by rotating the crankshaft while pressing on the engine timing pin.
Check/adjust the valves indicated for STEP A (I = intake; E = exhaust).
Tighten the rocker lever locknut and recheck valve clearance. Torque: 24 N•m [212 in-lb].
Disengage the timing pin; mark the vibration damper and rotate the crankshaft 360 degrees.
Set the valves indicated for STEP B; tighten the locknut and recheck the clearance.
Install a new rubber seal in the valve cover and new sealing o-rings on the capscrews.
Install the valve cover, wastegate sensing tube, and crankcase vent tube.

Adjusting Values/Parameters adjustment

⚠ If Home button or Previous Main Menu button is pressed before pressing save symbol, changes are not saved.

Press button next to symbol in display until + and − symbols are displayed.
Press button next to arrow symbols to move to numeric character to change.
Press button next to + symbol to increase value or select parameter.
Press button next to − symbol to decrease value or select parameter.
After adjusting values/selecting parameters, press symbol to save changes.

Electric Governor Calibration Checks adjustment

Tools: Frequency meter or tachometer

Start the generator set.
Set no-load speed for desired droop (isochronous 60.0 Hz/1800 r/min).
With no load, turn GAIN clockwise until actuator lever oscillates; reduce until stable.
Reduce GAIN one division, then turn fully clockwise while observing lever.
Turn I adjustment counterclockwise until lever stable; it should oscillate up to 3 times.
Apply and remove loads to check response; recalibrate if unsatisfactory.

Electric Governor Preliminary Adjustments adjustment

Tools: Screwdriver

Set frequency adjust (engine speed) potentiometer to mid position and tighten locking nut.
Set I potentiometer one division from zero.
Set Gain potentiometer at the third division from zero.
For isochronous operation turn Droop potentiometer fully counterclockwise.
Turn droop screw to approximately 40 for 3 percent droop.
Turn droop screw to approximately 80 for 5 percent droop.

Fuel Pump Control: Convert 120 VAC to 240 VAC adjustment

Remove jumpers between TB1-5/TB1-6 and TB1-7/TB1-8; connect two jumpers between TB1-6 and TB1-7.
Move selector switch S103 on control PCB to down position for 240 VAC.
If equipped with a transformer, remove jumpers between H1/H3 and H2/H4 and connect two jumpers between H2 and H3.
Attach a tag to the control box indicating the supply voltage.

Fuel Pump Control: Convert 240 VAC to 120 VAC adjustment

Remove jumpers between TB1-6/TB1-7; connect one jumper TB1-5 to TB1-6 and one TB1-7 to TB1-8.
Move selector switch S103 on control PCB to up position for 120V.
If equipped with a transformer, remove jumpers between H2/H3 and connect one between H1-H3 and one between H2-H4.

Idle Speed - Adjustment adjustment

Tools: Screwdriver, Tachometer, 13, 19 and 10 mm wrenches

Industrial: loosen locknut and back out the bumper spring screw.
Speed should drop 20-30 rpm as the screw is backed out.
Loosen locknut; set idle screw 20-30 rpm less than desired speed.
Turn idle screw counterclockwise to decrease rpm; clockwise to increase.
Turn bumper spring screw in until desired idle speed is obtained.
Tighten the locknut.
Automotive: loosen locknut and turn screw counterclockwise to raise rpm, clockwise to decrease.

Mechanical Governor Speed Adjustment adjustment

Tools: Frequency meter or tachometer, Wrench

Use the frequency control meter (if equipped) or an accurate tachometer.
Loosen the speed adjustment screw locknut.
Start set, warm to operating temperature, then apply full rated load.
Adjust speed adjust screw in or out to reach required speed (60 Hz - 1800 r/min, 50 Hz - 1500 r/min).
Hold screw at proper setting and retighten locknut.
Remove and apply loads to check response; readjust if necessary.

Overspeed Setpoint Adjustment and Testing adjustment

⚠ Do not exceed 120% of rated speed.

Tools: Signal generator (0.25 to 120 VAC RMS)

Lower the cover on the engine's local control panel.
Disconnect the engine speed sensor signal from PICK-UP terminals 1 and 2.
Connect a signal generator capable of providing 0.25 to 120 VAC RMS proportional to the engine's rated speed.
Remove the calibrating screw cover from the electronic overspeed switch.
Turn the potentiometer screw clockwise to increase trip speed, counter-clockwise to reduce trip speed.
Adjust until the OVERSPEED light is just illuminated at the desired setpoint.
Replace the screw cover, disconnect the signal generator, reset the light, and reconnect the speed sensor input.

Valves - Adjustment adjustment

⚠ Be sure to disengage the engine timing pin after locating TDC

Tools: Screwdriver, 13, 14, 15 and 18 mm wrenches, Feeler gauge, Barring gear Part No. 3904682

Remove air crossover tube, support clamps and crankcase vent tube.
Remove the valve cover.
Locate Top Dead Center for cylinder number 1 using barring gear and timing pin.
Check/set valves with engine cold, below 60C [140F].
Adjust the valves indicated for STEP A (intake then exhaust).
Tighten locknut to 24 Nm [18 ft-lb] and re-check valve lash.
Rotate crankshaft 360 degrees; be sure timing pin is disengaged.
Set the valves indicated for STEP B; tighten locknuts to 24 Nm [18 ft-lb].

Voltage Regulator Adjustment adjustment

⚠ Seated voltage regulator potentiometers are factory calibrated; further adjustments only by qualified service representative.

Tools: Screwdriver

Adjust voltage control rheostat R21 (if available) to mid position.
Open control panel doors to gain access to voltage regulator.
With set operating and voltage monitored, adjust Volts potentiometer to desired voltage.
Perform fine voltage adjustment (+/-3 percent) with rheostat R21, retighten locking nut.
Stop and restart generator set to confirm proper operation.

Battery Testing - Check Specific Gravity diagnostic

⚠ Batteries can emit explosive gases. Always ventilate the compartment before servicing the batteries.

⚠ Acid is extremely dangerous.

Tools: Hydrometer, Refractometer

Use a hydrometer to measure the specific gravity of each cell.
Check the battery fluid column in the refractometer to determine the state of charge of each battery cell.
If charge is low, charge the batteries.
Replace the battery if it will not charge to the manufacturer's specifications.

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	Notes
110/190	3
110/220	1
115/220	3
115/230	1	Generator voltage connections (reconnectable type only) per Figure 5-20; single phase double delta connection will reduce set rating and may not work with 3-phase meters
120/208	3
120/240	1
127/220	3
139/240	3
220/380	3
220/480	3
230/400	3
240/416	3
240/480	1
254/440	3
277/480	3

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 6CTA8.3 family

300

Part #	Description	Category
140-2241	Element, Air Cleaner	Air filter
140-2251	Element, Air Cleaner Secondary (Inner)	Air filter
140-2252	Element, Air Cleaner - Secondary (Inner)	Air filter
3833680	Bracket, Air Cleaner	Air filter
3837348	Cleaner, Air	Air filter
3919520	Bracket, Air Cleaner	Air filter
AC9055-01	Air Cleaner	Air filter
AF4669	Air Cleaner	Air filter
RU5045	Air Cleaner	Air filter
3016627	Alternator	Alternator
3016628	Alternator	Alternator
309-0272	Regulator, Voltage - 24 VDC (Used on 35 A MP Alternator)	Alternator
309-0561	Alternator & Drive Components Group Pulley. Alternator - Multi Groove (Use with 35 A MP Alternator)	Alternator
130-3216	V-belt	Belt
3897933	Bracket, Belt Guard	Belt
3897934	Bracket, Belt Guard	Belt
3897937	Bracket, Belt Guard	Belt
3911560	Belt, Drive - Alternator	Belt
3911562	Belt	Belt
3911571	Belt, Drive - Fan & Altr (6CTA Engine)	Belt
3921633	Guard, Belt	Belt
3922900	Tensioner, Belt	Belt
3925697	Bracket, Belt Tensioner	Belt
130-3536	Filter, Water - Service	Coolant filter
130-3539	Filter, Water - Pre-Charging	Coolant filter
WF2072	Coolant Filter	Coolant filter
405-5832	Door, Housing	Door
3377363	Lube Oil, Cummins Premium Blue 15W40 (one-gallon jugs)	Fluid
V70509	Lube Oil	Fluid
149-2250	Filter, Fuel - Primary	Fuel filter
149-2251	Filter, Fuel - Secondary	Fuel filter
3843760	Fuel Filter (Fleetguard FS1251 equivalent)	Fuel filter
FS1251	Fuel Filter	Fuel filter
102-1147	Gasket, Drain-Oil Pan	Gasket
102-1356	Gasket, Oil Drain	Gasket
3519762	Gasket, Turbocharger	Gasket
3914303	Gasket, Gear Housing (Front-Gear-Cover group BP9733-04)	Gasket
3914311	Gasket, Int Manifold Cover	Gasket
3916300	Gasket, Turbocharger	Gasket
3917779	Gasket, Gear Cover (Front-Gear-Cover group BP9733-04)	Gasket
3918779	Gasket, Connection	Gasket
3921691	Gasket, Exh Out Connection	Gasket
3931350	Gasket, Oil Drain	Gasket
3931608	Gasket, Acc Drive Cover	Gasket
406-0831	Hinge, Door	Hinge
106334	Hose, Plain	Hose
210753	Clamp, Hose	Hose
3025152	Hose, Plain	Hose
3283227	Coupling, Plain Hose	Hose
3905084	Hose, Flexible	Hose
3907167	Coupling, Plain Hose	Hose
3911875	Hose, Flexible	Hose
3911880	Coupling, Elbow Hose	Hose
3912183	Hose, Plain	Hose
3913724	Hose, Plain	Hose
3913751	Hose, Plain	Hose
3916529	Hose, Plain	Hose
3918163	Clamp, Hose	Hose
3918521	Clamp, Hose	Hose
3918607	Hose, Elbow	Hose
3918611	Hose, Plain	Hose
3920762	Hose, Elbow	Hose
3925025	Hose, Molded	Hose
3931970	Hose, Plain	Hose
501-0441	Line, Fuel - Flex (Fuel In)	Hose
503-0197	Clip, Hose	Hose
503-0365	Clamp, Hose	Hose
503-0446	Clamp, Hose	Hose
503-0465	Clamp, Hose	Hose
503-0685	Clamp, Hose	Hose
503-1195	Hose (3/4"ID x 24"LG)	Hose
503-1379-01	Hose, Radiator	Hose
503-1595	Hose	Hose
503-1599	Hose, Radiator	Hose
155-3150-04	Muffler, Critical	Muffler
502-0047	Nipple, Pipe (1/4)	Nipple
122-0756	Element - Oil Filter	Oil filter
3318853	Combination Full-Flow/Bypass Lubricating Oil Filter	Oil filter
LF9009	Lube Filter	Oil filter
102-1237	Adapter, Drain-Oil	Service part / kit
102483	End, Control Rod	Service part / kit
108722	Clip	Service part / kit
127007	Screw, Pan Head Cap	Service part / kit
130-3212	Advanced Efficiency Hydraulic/Transmission Filter	Service part / kit
140-1260	Fitting, Safety Filter	Service part / kit
140-1548	Indicator, Service	Service part / kit
140-2240	Cleaner, Air (Incl Element)	Service part / kit
140332	Clamp, T Bolt	Service part / kit
146159	Washer, Plain	Service part / kit
146160	Washer, Plain	Service part / kit
155-2307	Silencer	Service part / kit
180371	Clip	Service part / kit
203555	Connection, Exhaust Outlet	Service part / kit
204991	Washer, Plain	Service part / kit
213365	Screw, Hexagon Head Cap	Service part / kit
3007636	Plug, Expansion	Service part / kit
3008468	Plug, Pipe 1/2 NPT	Service part / kit
3010596	Screw, Captive Washer Cap	Service part / kit
3018006	Screw, Hexagon Head Cap	Service part / kit
3026910	Cable	Service part / kit
3028870	Connection, Tur Oil Inlet	Service part / kit
3030871	Gauge, Pressure	Service part / kit
3030872	Gauge, Temperature	Service part / kit
3031348	Flange, Power Takeoff	Service part / kit
3031643	Rectifier	Service part / kit
3032105	Bearing, Ball	Service part / kit
3033379	Control, Vernier	Service part / kit
3033800	Washer, Plain	Service part / kit
3035083	Isolator, Vibration	Service part / kit
3035084	Isolator, Vibration	Service part / kit
3039554	Switch, Push Button	Service part / kit
3039570	Ammeter	Service part / kit
3049554	Hourmeter & Tachometer	Service part / kit
3050323	Speed Switch, Electronic	Service part / kit
309-0553	Switch, Temperature-Pre Water	Service part / kit
309-0554	SWITCH WATER	Service part / kit
3175239	Nut, Lock	Service part / kit
3284244	Connector, Female	Service part / kit
332-1473	Lug, Solderless	Service part / kit
3393823	Bolt, Carriage	Service part / kit
3885910	Red Paint, Spray can	Service part / kit
3900629	Screw, Hex Flange Head Cap	Service part / kit
3900630	Screw, Hex Flange Head Cap	Service part / kit
3900631	Screw, Hex Flange Head Cap	Service part / kit
3900632	Screw, Hex Flange Head Cap	Service part / kit
3900633	Screw, Hex Flange Head Cap	Service part / kit
3901249	Screw, Hex Flange Head Cap	Service part / kit
3901757	Screw, Hex Flange Head Cap	Service part / kit
3902115	Screw, Hex Flange Head Cap M12 x 1.75 x 65	Service part / kit
3902468	Cap, Filler	Service part / kit
3902662	Nut, Hexagon Flange	Service part / kit
3903463	Cover, Access Hole	Service part / kit
3903990	Screw, Hex Flange Head Cap	Service part / kit
3904971	Connection Water Transfer	Service part / kit
3905156	Shim A/R 1.00 mm Thick	Service part / kit
3905157	Shim A/R 1.04 mm Thick	Service part / kit
3905158	Shim A/R 1.08 mm Thick	Service part / kit
3905159	Shim A/R 1.10 mm Thick	Service part / kit
3905160	Shim A/R 1.14 mm Thick	Service part / kit
3905161	Shim A/R 1.18 mm Thick	Service part / kit
3905162	Shim A/R 1.20 mm Thick	Service part / kit
3905163	Shim A/R 1.24 mm Thick	Service part / kit
3905164	Shim A/R 1.28 mm Thick	Service part / kit
3905165	Shim A/R 1.30 mm Thick	Service part / kit
3905166	Shim A/R 1.34 mm Thick	Service part / kit
3905167	Shim A/R 1.38 mm Thick	Service part / kit
3905168	Shim A/R 1.40 mm Thick	Service part / kit
3905169	Shim A/R 1.44 mm Thick	Service part / kit
3905170	Shim A/R 1.48 mm Thick	Service part / kit
3905171	Shim A/R 1.50 mm Thick	Service part / kit
3905172	Shim A/R 1.54 mm Thick	Service part / kit
3905173	Shim A/R 1.58 mm Thick	Service part / kit
3905174	Shim A/R 1.60 mm Thick	Service part / kit
3905175	Shim A/R 1.64 mm Thick	Service part / kit
3905176	Shim A/R 1.68 mm Thick	Service part / kit
3905177	Shim A/R 1.70 mm Thick	Service part / kit
3905178	Shim A/R 1.74 mm Thick	Service part / kit
3905180	Shim A/R 1.78 mm Thick	Service part / kit
3905181	Shim A/R 1.80 mm Thick	Service part / kit
3905182	Shim A/R 1.84 mm Thick	Service part / kit
3905183	Shim A/R 1.88 mm Thick	Service part / kit
3905184	Shim A/R 1.90 mm Thick	Service part / kit
3905185	Shim A/R 1.94 mm Thick	Service part / kit
3905186	Shim A/R 1.98 mm Thick	Service part / kit
3906436	Tube, Water Inlet	Service part / kit
3906439	Plate, Clamping	Service part / kit
3906619	Plug, Pipe	Service part / kit
3906715	Screw, Hex Flange Head Cap	Service part / kit
3906733	Screw, Hex Flange Head Cap	Service part / kit
3907978	Stud M10 x 1.50(Both Ends) x 50	Service part / kit
3908402	Tube, Water Outlet	Service part / kit
3910901	Screw, Hex Flange Head Cap	Service part / kit
3911670	Manifold, Exhaust	Service part / kit
3912151	Plate, Clamping	Service part / kit
3912159	Connection, Water Outlet	Service part / kit
3914502	Aftercooler	Service part / kit
3914868	Plate, Cover	Service part / kit
3915772	Seal, Rectangular Ring (Front-Gear-Cover group BP9733-04)	Service part / kit
3916326	Connection, Exhaust Outlet	Service part / kit
3916518	Screw, Hex Flange Head Cap M10 x 1.50 x 125	Service part / kit
3916585	Screw, Hexagon Head Cap	Service part / kit
3917394	Connection, Water Transfer	Service part / kit
3918109	Screw, Hex Flange Head Cap M8 x 1.25 x 25	Service part / kit
3918192	Washer, Sealing	Service part / kit
3918498	Screw, Hex Flange Head Cap M10 x 1.50 x 145	Service part / kit
3918500	Tube, Air	Service part / kit
3918542	Spacer, Mounting	Service part / kit
3918927	Connection Water Transfer	Service part / kit
3919461	Block, Terminal	Service part / kit
3919462	Harness, Wiring	Service part / kit
3919465	Cabinet, Instrument	Service part / kit
3919467	Decal	Service part / kit
3919563	Tube, Water Transfer	Service part / kit
3919577	Heater, Engine	Service part / kit
3919578	Panel, Instrument	Service part / kit
3919585	Panel, Eng Instrumentation	Service part / kit
3919687	Connector, Female	Service part / kit
3919748	Dataplate	Service part / kit
3919750	Brace, Exh Out Connection	Service part / kit
3919751	Shield, Heat	Service part / kit
3919814	Connection, Tur Oil Drain	Service part / kit
3919815	Tube, Tur Oil Drain	Service part / kit
3919871	Bracket, Cable	Service part / kit
3921533	Shield, Dust	Service part / kit
3921724	Tag, Identification	Service part / kit
3923360	Plate, Clamping	Service part / kit
3924389	Washer, Sealing	Service part / kit
3924798	Shaft, Idler	Service part / kit
3925186	Screw, Flat Head Cap	Service part / kit
3925568	Damper, Vibration	Service part / kit
3925749	Connector, Banjo	Service part / kit
3925883	Screw, Hex Flange Head Cap	Service part / kit
3926125	Screw, Hexagon Head Cap	Service part / kit
3926901	Pulley, Idler	Service part / kit
3930678	Tube, Vent	Service part / kit
3930903	Cover, Valve	Service part / kit
3931827	Tube, Tur Oil Drain	Service part / kit
402-0030	Part 402-0030	Service part / kit
41320-D	Shaft, Stub	Service part / kit
416-0444	Cable, Battery - Negative	Service part / kit
416-0619	Cable, Battery	Service part / kit
501-0480	Line, Fuel - Flex (Fuel Out)	Service part / kit
504-0011	Valve, Shutoff (1/2”)	Service part / kit
505-0021	Bushing, Pipe - Reducer (3/4º to 1/2º)	Service part / kit
505-0050	Elbow, Street (1/2' x 90 ° )	Service part / kit
505-0185	Nipple, Half (1/2' x 1.5' lg)	Service part / kit
508-0015	Washer, Insulating - Fiber (#8)	Service part / kit
508-0231	Bumper Switch, Selector	Service part / kit
526-0003	#Washer, Flat (#8)	Service part / kit
526-0008	148-036’?	Service part / kit
526-0219	Washer, Flat (1/2)	Service part / kit
526-2140	Washer, Flat (M12)	Service part / kit
554802	Washer, Plain	Service part / kit
5818824	Nut, Hexagon Flange M10 x 1.50	Service part / kit
62399-N	Key, Square	Service part / kit
70208	Screw, Pan Head	Service part / kit
800-0008	Screw, Cap - Hex Head (1/'4-2Ox 1-1/4')	Service part / kit
800-0026	Screw, Cap - Hex Head (5/16-18 X 3/4')	Service part / kit
800-0091	Part 800-0091	Service part / kit
800-0520	Screw, Cap - Hex Head - Self Locking 3/4-10 x 1"	Service part / kit
800-2058	Screw, Cap - Hex Head (M8 x 1.25 x 25)	Service part / kit
800-2088	Screw, Cap - Hex Head	Service part / kit
800-2110	Hood, Inlet - Air Molded	Service part / kit
800-2111	Screw, Cap - Hex Head (M12 x 1.25 x 25mm)	Service part / kit
809-0035	Screw, Machine - Thread Cutting, Round Head (#8 X 3/4')	Service part / kit
815-0172	Cover, Adapter Outlet	Service part / kit
818-0150	Rivet	Service part / kit
821-0014	2 821-0018 1 3 526-0018 2 4 856-0006 1 5 870-0212 1 6 NOTE 1 REF 7 NOTE 1 REF 8 NOTE 1	Service part / kit
821-0018	Screw, Self-locking - Hex Washer Head ( 1'4.20 x 5 8')	Service part / kit
821-0029	Screw, Self–Locking – Hex Washer Head (3/8–16 x 3/4")	Service part / kit
821-6003-02	Screw, Cap - Hex Head (M8 x 1.25 x 25mm)	Service part / kit
850-0030	Washer, Lock - Spring (#10)	Service part / kit
850-0060	Screw, Cap - Hex Head (5/16-18 X 7-1/2" )	Service part / kit
850-2005	Washer, Lock - Spring (M5)	Service part / kit
850-2008	Washer, Lock (M8)	Service part / kit
850-2010	Lock	Service part / kit
850-2012	Washer, Lock - Spring (M12)	Service part / kit
856-0008	Washer, Lock - EIT (5/16'1)	Service part / kit
856-0013	Washer, Lock - W/EIT (1/2)	Service part / kit
860-2006	Genset component (SJB series)	Service part / kit
862-0004	4 ttNut, Hex - Set Mounting - Key 2 HARDWARE SET, SET MOUNTING	Service part / kit
862-0016	Nut, Hex	Service part / kit
863-0002	Cleaner, Air (Includes Element)	Service part / kit
870-0048	Nut, Self-locking - Hex (5/16-18)	Service part / kit
870-0053	Nut, Hex (s10-32)	Service part / kit
870-0196	Nut, Insulating (#8)	Service part / kit
870-0212	Nut, Locking (1/4-20)	Service part / kit
870-0257	Nut, Locking (5/16−18) * − Parts Used On Heat Exchanger Installations With Automatic Water Regulator # − Cut Off And Discard Swivel Connector End Of Hose So That 1/8 NPT Connector End Measures Length As Indicated Above + − Parts Used On Heat Exchanger Installations Without Automatic Water Regulator	Service part / kit
870-0281	Nut, Self-Locking – Hex Washer Head (3/8–16)	Service part / kit
871-0010	Nut, Hex - Srass (#10-32) Washer, Lock - EIT (#10) Washer, Lock - IT (#10)	Service part / kit
S-1008-1	Connector, Female	Service part / kit
S-103-D	Screw, Hexagon Head Cap	Service part / kit
S-114	Screw, Hexagon Head Cap 1/4 - 20 X 3/4 Inch.	Service part / kit
S-115	Screw, Hexagon Head Cap	Service part / kit
S-118	Screw, Hexagon Head Cap	Service part / kit
S-118-A	Screw, Hexagon Head Cap	Service part / kit
S-168-C	Screw, Hexagon Head Cap	Service part / kit
S-224	Nut, Heavy Hexagon	Service part / kit
S-225	Nut, Heavy Hexagon Jam	Service part / kit
S-257	Nut, Regular Hexagon	Service part / kit
S-511	Pin, Cotter	Service part / kit
S-600	Washer, Lock 1/4 inch	Service part / kit
S-608	Washer, Lock	Service part / kit
S-622	Washer, Plain 3/8 inch	Service part / kit
S-907-B	Union, Plain Female	Service part / kit
S-920	Nipple, Plain Pipe	Service part / kit
S-960	Tee, Female Pipe	Service part / kit
S-962-E	Draincock	Service part / kit
405-5908	Panel, Side - Radiator Housing	Panel
405-5917	Panel, End - Roof	Panel
155-3164-01	Pipe, Exhaust	Pipe
405-5744	Post, Housing - Center	Post
405-5916	Post, Corner - Housing	Post
3802975	Pump, Water	Pump
3929614	Pump, Water	Pump
145530	Seal, O Ring	Seal
3819725	Clamp, Hose	Seal
3902089	Seal, O Ring	Seal
3902466	Seal, Rectangular Ring	Seal
3903475	Seal, Rectangular Ring	Seal

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 6CTA8.3-M (JW)?

The Cummins/Onan 6CTA8.3-M (JW) has a displacement of 8.3 liters with 6 cylinders.

Which generators use the Cummins/Onan 6CTA8.3-M (JW) engine?

The Cummins/Onan 6CTA8.3-M (JW) powers 1 generator set(s), including Cummins/Onan 6CTA8.3.

What is a common problem with the Cummins/Onan 6CTA8.3-M (JW) engine?

A commonly reported issue on generators using the Cummins/Onan 6CTA8.3-M (JW) is: Low power.