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Cummins/Onan 6CT8.3 Engine

The Cummins/Onan 6CT8.3 is a 8.3 L 6-cylinder turbocharged, aftercooled engine rated at 2200 rpm. It powers generator sets from AKSA and Cummins/Onan, including the AC 200, AC150, 6CT 8.3 and DGEA. It holds 19 L (5.0 gal) of oil and 26 L (6.9 gal) of coolant.

Also known as: CUMMINS 6CT8.3

Part of the Cummins/Onan 6CT8.3 engine family — 3 variants share parts & fitment.

8.3 L

Displacement

Cylinders

2200 rpm

Rated speed

19.0 L

Oil capacity

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

Engine specifications

Oil capacity	19.0 L
Coolant capacity	26.0 L
Displacement	8.3 L
Cylinders	6
Aspiration	Turbocharged, Aftercooled
Rated speed	2200 rpm

Generator sets powered by this engine

Shared across brands: AKSA, Cummins/Onan

AKSA AC 200AKSA AC150 Cummins/Onan 6CT 8.3 Cummins/Onan DGEA

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

Common problems

Low Power
Cause: Vehicle Overloaded
Fix: Reduce load or use lower gears.
Coolant Temperature Above Normal
Cause: Low Coolant Level
Fix: Add coolant.
Exhaust Smoke Excessive Under Load
Cause: Lugging Engine
Fix: Use lower gear.
Engine will not crank
Cause: Fault lamp on
Fix: Correct fault and reset control.
Excessive Fuel Consumption
Cause: Fuel Leak
Fix: Check for source of the leak.
Engine Hard to Start or Will Not Start (Exhaust Smoke Present)
Cause: Engine Cranking Speed to Slow
Fix: Refer to Engine Will Not Crank or Cranks Slowly
Lube Oil Loss
Cause: External Leaks
Fix: Visually Inspect for Oil Leaks.
Engine Will Not Reach Rated Speed When Loaded
Cause: Vehicle Overloaded
Fix: Reduce load or use lower gear.
Engine Starts But Will Not Keep Running
Cause: Idle Speed Too Low
Fix: Adjust idle speed.
Rough Idle, Warm Engine
Cause: Idle Speed Set too Low
Fix: Check/adjust low idle screw setting.
Lubricating Oil Pressure Low
Cause: Incorrect Oil Level
Fix: Add or drain engine oil.
Engine Will Not Crank or Cranks Slowly
Cause: Starting Motor Operating But Not Cranking the Engine
Fix: Remove the starting motor and check for broken teeth on the flywheel or broken spring.
Engine Cranks, But Will Not Start - No Smoke From Exhaust
Cause: No Fuel in Tank
Fix: Add fuel.
Fuel or Oil Leaking from Exhaust Manifold
Cause: Intake Air Restriction
Fix: Check/Replace Filter Element.
Excessive Vibration
Cause: Engine Not Running Smoothly
Fix: Refer to Troubleshooting Logic for rough running or misfiring.

Compiled from service & troubleshooting documentation across every generator set that uses the Cummins/Onan 6CT8.3.

Maintenance schedule

Item	Spec	Capacity	Part #	Interval
Air filter	Every 33,000 KM [20,000 Miles], 1,000 Hours Or 1 Year Maintenance And The Following.		—	1000 hr
Fuel filter	Fuel Filter		—	2500 hr
Oil filter	Lube Filter		—	8000 hr
Battery	Air Cleaner Element		—	8000 hr
Belt	Drive Belt		—	2500 hr
Coolant	Every 64,000 KM [40,000 Miles], 2,000 Hours Or 2 Years Interval		—	2000 hr
Coolant filter	Coolant Filter		—	8000 hr
Oil	Lube Oil	235.0 Litres [4 U.S. Quarts]	—	2000 hr
Spark plug	Every 64,000 KM [40,000 Miles], 2,000 Hours Or 2 Years Interval		—	2000 hr

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

Repair guides

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

Service intervals

Item	Action	Hours	Months	Notes
Check Coolant Level	Check	8 hr		Daily
Check Fuel Level	Check	8 hr		Daily
Check Oil Level	Check	8 hr		Daily
Coolant Heater	Check	8 hr		Verify hot coolant is being discharged from the outlet hose.
Coolant Level	Check	8 hr
Drain Water from Fuel Filter	Drain	8 hr		Daily; drain 1 cup or more of fuel to remove water and sediment.
Exhaust Condensate Trap	Drain	8 hr
Fuel Filter(s)	Drain	8 hr		Drain 1 cup or more of fuel to remove water and sediment. Refer to engine operation and maintenance manual for procedure.
Fuel Level	Check	8 hr
Fuel Tanks (water and sediment)	Drain	8 hr		Drain 1 cup or more of fuel to remove water and sediment.
Inspect Genset	Check	8 hr		Check for oil, fuel, cooling and exhaust system leaks. Check exhaust system audibly and visually with set running and repair any leaks immediately.
Inspect Set	Inspect	8 hr		Daily; check for oil, fuel, cooling, and exhaust system leaks.
Oil Level	Check	8 hr		Keep oil level near the dipstick high mark without overfilling.
Air Cleaner	Clean	50 hr		Clean if required. Perform more often in dusty conditions.
Battery Charging System	Check	50 hr
Charge Air Piping	Check	50 hr
Check Anti-freeze and DCA Concentration	Check	50 hr		Weekly
Check Battery Charging System	Check	50 hr		Weekly
Check Battery Level and Specific Gravity	Check	50 hr		Weekly
Check Coolant Heater	Check	50 hr		Weekly
Check Drive Belt Tension	Check	50 hr		Weekly; visually check belts for evidence of slippage.
Check Generator Air Outlet	Check	50 hr		Weekly
Crankcase Oil	Drain	50 hr		First service — Break-in: drain and replace the crankcase oil after the first 50 hours of operation on new generator sets.
Crankcase oil	Change	50 hr		First service — Drain and replace after first 50 hours of operation on new generator sets.
Drain Exhaust Condensate Trap	Drain	50 hr		Weekly
Drain Water and Sediment from Fuel Tanks	Drain	50 hr		Weekly; drain 1 cup or more.
Starting Batteries	Check	50 hr
Check Air Cleaner (clean if required)	Check	100 hr		Monthly; clean if required; perform more often in extremely dusty conditions.
Clean Generator Assembly	Clean	100 hr		Monthly
Air Cleaner	Inspect	250 hr	3 mo	Every 8,000 km [5,000 mi]
Anti-freeze and DCA Concentration	Check	250 hr	3 mo	Refer to engine operation and maintenance manual.
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]
Coolant Filter	Replace	500 hr	6 mo	Every 8,000 km [5,000 mi]
Crankcase Oil and Filter	Change	250 hr	3 mo	If genset is used for prime power applications, change oil and filter every 3 months or 250 hours. If used for standby applications, change oil every 12 months or 250 hours, whichever comes first.
Damper	Inspect	250 hr	3 mo	Every 8,000 km [5,000 mi]
Drive Belt Tension	Check	250 hr	3 mo	Visually check belt for evidence of wear or slippage. Replace if hard or brittle. Refer to engine operation and maintenance manual.
Fan Hub	Inspect	250 hr	3 mo	Every 8,000 km [5,000 mi]
Fuel Filters	Change	250 hr	3 mo	Refer to engine operation and maintenance manual.

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	Float switch lift below C-clip stop	1/8	inch (3 mm)
Clearance	Overspeed switch magnet-to-fly arm air gap (minimum)	0.005	inches (0.13 mm)
Clearance	Vibration damper index line misalignment (replace if exceeded)	1.59	mm [1/16 inch]
Gap	Mechanical overspeed switch air gap between magnet and fly arm (replace switch if less)	0.005	inches (0.13 mm)
Gap	Overspeed switch air gap	0.005 in. / 0.13 mm	in / mm
Injection timing	Timing	22	°BTDC
Other	AVR DROOP preset at factory	five percent droop at full load and zero power factor
Other	Battery electrolyte corrected specific gravity (fully charged)	1.260		electrolyte temperature corrected
Other	Battery recharge threshold specific gravity	1.215
Other	Battery specific gravity	1.260		at 77°F (25°C)
Other	Battery specific gravity temperature correction	four gravity points (0.004) for every ten degrees above 80 F (27 C)
Other	Battery specific gravity, fully charged	approximately 1.260	at 80°F (27°C)
Other	Coolant level	50	mm	below radiator cap opening
Other	Cycle crank crank and rest time	7 to 20	seconds
Other	Cycle crank number of cycles	3, 4, or 5
Other	Cycle cranking (12-lamp control)	3 cycles of 15 seconds
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	ECM fuse F1 (starter solenoid circuit)	20	amps
Other	ECM fuse F2 (fuel solenoid circuit)	20	amps
Other	ECM fuse F3 (continuous B+ to remote circuits)	15	amps
Other	ECM fuse F4 (ECM circuits)	5	amps
Other	ECM fuse F5 (engine gauge circuits)	5	amps
Other	Firing order	153624
Other	Frequency adjustment range	±5%	%	genset running
Other	Fuse A31-F1 (control B+)	5	Amp	Engine Interface board
Other	Fuse A31-F3 (auxiliary B+)	5	Amp	Engine Interface board; panel lights, run and start relays
Other	Fuse A38-F1 (Network B+)	10	Amp	Governor Output Module
Other	Fuse A38-F2 (Switched B+)	10	Amp	Governor Output Module
Other	Fuse A38-F3 (Governor B+)	10	Amp	Governor Output Module
Other	Fuse TB-Bat F1 (Customer B+)	20	Amp	Engine Harness Assembly
Other	GOV RAMP adjustment range	0 through 10	seconds
Other	Generator voltage adjustment range via rheostat R21	+/-3 percent of rated nameplate voltage	percent
Other	Governor droop adjustment range	within 5	percent of nominal frequency (3 Hz for 60Hz sets, 2.5 Hz for 50Hz sets)
Other	LOP and HET fault time delay following starter disconnect	about 10 seconds	seconds
Other	Low oil pressure / high engine temperature fault time delay	about 10	seconds	following starter disconnect and inhibited during cranking
Other	Over/under voltage module time delay (to prevent nuisance tripping)	25 percent, or approximately 2.5 seconds	percent / seconds
Other	Overcrank limit (Sentinel)	60	seconds
Other	Overcrank limit (three 15-second cranking cycles with two 15-second rest periods)	75 seconds	seconds
Other	Overcrank option limit (Detector)	75	seconds
Other	Overcrank time limit	75	seconds
Other	Overspeed module time delay	typically one second	seconds
Other	Overspeed warning range 60 Hz sets	2000 to 2200	RPM
Other	REG VHZ adjustment range	1 through 50 (normal range 7 through 21)
Other	Random voltage variation	±1	%	for constant loads
Other	Response jumper setting - 90 to 550 kW	B to C
Other	Response jumper setting - over 550 kW	A to B
Other	Response jumper setting - under 90 kW	A to C
Other	Setup/calibration menu access code	574
Other	Standard cycle cranking (Detector)	three 15-second cranking cycles with two 15-second rest periods
Other	Start delay adjustment range	0 to 300	seconds	remote starting in Auto mode
Other	Starter disconnect speed	450 to 570	RPM
Other	Stop delay adjustment range	0 to 600	seconds	remote stopping in Auto mode
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
Other	Trailer brake shoe adjustment back-off	10	clicks
Other	Trailer surge brake actuator stroke length (service brakes if exceeds)	1	inch (25 mm)
Other	Under-frequency roll-off (UFRO) threshold, 50 Hz applications	49	Hz
Other	Under-frequency roll-off (UFRO) threshold, 60 Hz applications	59	Hz

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		soft water/E.G./DCA mixture			Installation review checklist item: cooling system must be filled with soft water/E.G./DCA mixture.
Coolant	50/50 mix of water and antifreeze	Balanced coolant mixture of water, antifreeze and coolant additives			Drain and replace the mixture every 6 months or after 500 hours of operation. Do not add cold coolant to a hot engine; allow engine to cool below 120 F (50 C) before adding coolant.
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 the Cummins engine Operation and Maintenance Manual for lubricating oil classification/recommendations/specifications			Gensets are shipped with oil added.
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
Engine oil	SAE 5W synthetic	API CC/CD; sulphated ash max 1.85%; pour point 9°F (5°C) below lowest expected temperature; viscosity max 10,000 mPa·s at -31°F (-35°C) and min 4.1 mm²/s at 212°F (100°C)	below -23°C		For ambient consistently below -10°F (-23°C) and no engine warm-up provision
Engine oil	10W-30	API CC/CD	-23°C to -10°C		For ambient -10°F (-23°C) to 14°F (-10°C)
Engine oil	15W-40	API CC/CD	above -10°C		For ambient 14°F (-10°C) and above
Engine oil	20W-40	API CC/CD	above 0°C		For ambient 32°F (0°C) and above
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	No. 2 diesel				Engine primarily designed for No. 2 diesel; No. 1 fuel or similar acceptable if meets specifications
Fuel	diesel				Do not use zinc coated or copper fuel lines with diesel fuel.
Hydraulic oil	DOT-3				Trailer master cylinder reservoir - keep at least half full
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
101	IDLE MODE	Indicates that the engine is operating in idle mode. Grounding the engine idle input inhibits generator build-up and governs the engine at 800 RPM; control lowers oil pressure warning and shutdown trip points accordingly.	Warning	None required; removing ground returns the genset to normal speed and voltage.
102	EMERGENCY STOP	Indicates local or remote Emergency Stop.	Shutdown	Pull the button out (turn clockwise to allow it to pop out); move Run/Off/Auto switch to Off; press the Reset switch; select Run or Auto as required. Reset only at the PCC front panel.
200	LOW OIL PRESSURE	Indicates engine oil pressure has dropped to an unacceptable level.	Warning	If powering critical loads and cannot be shut down, wait until next shutdown period then follow the 201-SHUTDOWN procedure. Check oil pressure via the Oil Pressure menu prior to clearing the fault.
201	LOW OIL PRESSURE	Indicates engine oil pressure has dropped below the shutdown trip point.	Shutdown	Check oil level, lines and filters; if oil system is OK but oil level is low, replenish; reset control and restart. Oil pressure limits are listed in Table 4-3.
204	OIL PRES SENDER	Indicates that the control has sensed that the engine oil pressure sender is out of its working range.	Warning	Check that the engine oil pressure sender is properly connected.
210	LOW COOLANT TEMP	Warning occurs when engine coolant temperature is 70 deg F (21 deg C) or lower while set is not operating.	Warning	Indicates engine coolant heater is not operating or is not circulating coolant; check coolant heater power supply/fuse, low coolant level, and open heater element.
211	HIGH COOLANT TEMP	Indicates engine coolant temperature is getting close to the recommended maximum (215 deg F/102 deg C standby or 207 deg F/97 deg C prime).	Warning	Reduce load if possible; check air inlets and outlets and remove obstructions to airflow; if engine can be stopped follow the 212-SHUTDOWN procedure.
212	HIGH COOLANT TEMP	Indicates engine has overheated (coolant above 223 deg F/106 deg C standby or 215 deg F/102 deg C prime).	Shutdown	Allow engine to cool; check for obstructions to cooling airflow, check fan belt, check coolant mixture, check blower fan and circulation pumps; reset control and restart after correcting problem.
213	COOLANT SENDER	Indicates that the resistance of the coolant temperature sender is out of range.	Warning	Check the resistance of the sender (should be 500 to 2k ohms).
214	LOW COOLANT LVL	Indicates engine coolant level has fallen below the trip point.	Warning	Allow engine to cool; check coolant level in radiator and recovery bottle and replenish if low; check for possible coolant leakage points.
215	LOW COOLANT LVL	Indicates engine coolant level has fallen below the shutdown trip point.	Shutdown	Check coolant level in radiator and recovery bottle and replenish if low; check defective coolant bottle hose or radiator cap; reset control and restart after correcting problem. Will not occur in Idle mode.
220	MAG PICKUP	Indicates mag pickup speed indication is not being sensed or does not match generator set output frequency.	Shutdown	Restart and check RPM on the digital display; isolate per troubleshooting table 4-18.
221	FAIL TO CRANK	Indicates possible fault with control or starting system.	Shutdown	Check fuse F3 on the Engine Interface board; clean battery cable connections; recharge or replace battery.
222	OVERCRANK	Indicates possible fuel system problem.	Shutdown	Check for empty fuel tank, fuel leaks, or plugged fuel lines; check for dirty fuel filter and replace; check for dirty or plugged air filter and replace; reset control and restart.
223	OVERSPEED	Indicates engine has exceeded normal operating speed (115% +/-1% of nominal).	Shutdown	Inspect mechanical fuel linkage; check EFC for binding/damage; monitor PCC duty cycle and replace A32 or A38 as indicated.
224	FAIL TO SYNCHRONIZE	The generator set has not synchronized to the system bus within the allowable time frame.		Check governor system stability and adjust governing/synchronizer parameters; check for fuel system problems causing engine instability; widen synchronizing window and reduce acceptance time delay.
226	FAIL TO CLOSE	Indicates that the paralleling breaker has been given a signal to close, but has not closed properly.		Verify charging mechanism of paralleling breaker; check the close signal to the breaker; verify auxiliary contact signals from the breaker to the control are operational.
230	LOW DC VOLTAGE	Indicates battery voltage is below 10 VDC.	Warning	Check battery charger fuse and recharge or replace battery; clean and tighten battery cable connections; check engine DC alternator; check battery charge voltage float level.
231	HIGH DC VOLTAGE	Indicates battery voltage exceeds 32 VDC.	Warning	Check voltage float level on battery charger (lower float level); check engine DC alternator and replace if normal charging voltage is not obtained.
232	WEAK BATTERY	Indicates battery voltage drops below 60% of nominal for two seconds during starting.	Warning	Discharged or defective battery; see warning message 230, LOW DC VOLTAGE.
240	LOW FUEL-DAY	Indicates day tank fuel supply is running low.	Warning	Check fuel supply and replenish as required.
241	LOW FUEL	Indicates fuel supply is running low.	Warning	Check fuel supply and replenish as required.
250	EEPROM ERROR	Indicates PCC memory error - data corruption of critical operating parameters.	Shutdown	Perform initial start setup; turn Run/Off/Auto to Off and reset; if the same EEPROM ERROR message occurs, replace the digital board (A32).
251	EEPROM ERROR	Indicates PCC memory error - data corruption of noncritical operating parameters.	Warning	Perform adjustment procedures and save; if the same EEPROM ERROR message occurs, replace the digital board (A32).
252	EEPROM ERROR	Indicates PCC memory error - data corruption of noncritical operating parameters.	Warning	Verify values/choices selected and repeat the save operation; if the same EEPROM ERROR message occurs, replace the digital board (A32).
260	CUSTOMER FAULT 1	Customer defined input closed to ground; message is editable.		Isolate the source of the false signal; check A34 LED corresponding to the fault input.
261	GROUND FAULT	Customer defined input closed to ground (default message); message is editable.		Isolate the source of the false signal; check A34 LED corresponding to the fault input.
262	RUPTURE BASIN (DAY TANK)	Customer defined input closed to ground; message is editable.		Isolate the source of the false signal; check A34 LED corresponding to the fault input.
263	HIGH GEN TEMP	Customer defined input closed to ground (default message); message is editable.		Isolate the source of the false signal; check A34 LED corresponding to the fault input.
270	PHASE ROTATION	The phase relationship between the generator set and the system bus is not matched.	Shutdown	Using a phase rotation checker, verify that the generator set phase rotation matches the system bus; verify control wiring to the bus PT module is properly connected.
272	FIRST START	The PowerCommand control is not receiving a proper signal from the system master first start sensor.	Warning	Control reverts to fallback mode; verify the Master First Start Sensor is functioning and that the voltage pulse is present at the PowerCommand control (terminal TB1-50); check interconnection wiring.
301	HIGH AC VOLTAGE	Indicates that one or more phase voltages has exceeded 130% of nominal, or exceeded 110% of nominal for 10 seconds.	Shutdown	Isolate the regulator module (A37), engine interface board (A31), digital board (A32), PMG/field wiring or PT/CT sensing path per troubleshooting table 4-29.
303	LOW AC VOLTAGE	Indicates that one or more phase voltages has dropped below 85% of nominal for 10 seconds.	Shutdown	Check PMG or field wiring, rotating rectifier diodes, overload, loose connectors, and voltage sensing circuitry per troubleshooting table 4-30.
313	UNDER FREQUENCY	Indicates that engine speed has dropped below 90% of nominal for 10 seconds. (Five seconds before shutdown, a Load Dump signal is initiated.)	Shutdown	Check fuel supply, intake air supply and load; check Initial Setup (set size).
320	OVERCURRENT	Indicates that generator output current has exceeded 110% of rated for 60 seconds.	Warning	Check load and load lead connections.
321	OVERCURRENT	Indicates that generator output current has exceeded 110% of rated, and a PCC time/current calculation has initiated an overcurrent shutdown.	Shutdown	Check load and load lead connections.
322	SHORT CIRCUIT	Indicates that generator output current has exceeded 175% of rated.	Shutdown	Check load and load lead connections.
330	OVERLOAD	Indicates that three-phase power output exceeds 105% of standby (or 115% of prime) rating.	Warning	Check load and load lead connections.
335	REVERSE POWER	Indicates that power is flowing into the generator set rather than out from the unit.	Shutdown	Verify connection of generator set CT's; verify proper connection of load sharing lines; verify correct frequency and voltage on all sets.
337	LOSS OF EXCITATION	Indicates that the alternator excitation system is improperly adjusted or has failed.	Shutdown	Check output voltage with calibrated meter and adjust; check load sharing lines; see Section 6 Servicing the Generator.
BASIN	Day tank BASIN lamp	Fuel has overflowed into the rupture basin, indicating possible failure of pump-off and hi-fuel float switches or a leak in the day tank	Warning	RESET the control after fuel in the basin is safely disposed of and cause of overflow corrected
BLANK	Blank lamp	For customer use
F1	ECM fuse F1	Starter solenoid circuit, 20 amps		Replace with a fuse of the same type and amp rating
F2	ECM fuse F2	Fuel solenoid (switched B+) circuits, 20 amps		Replace with a fuse of the same type and amp rating
F3	ECM fuse F3	Continuous B+ out to remote circuits, 15 amps		Replace with a fuse of the same type and amp rating
F4	ECM fuse F4	ECM circuits, 5 amps		Replace with a fuse of the same type and amp rating
F5	ECM fuse F5	Engine gauge circuits, 5 amps		Replace with a fuse of the same type and amp rating
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 1 (Red)	Fault 1 (Detector-12)	Engine shut down because of a system fault; part of a 10 second time delay shutdown circuit (customer connections)	Shutdown	Service as required; selection jumpers may choose warning only or non-timed shutdown
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
Fault 2 (Red)	Fault 2 (Detector-12)	Engine shut down because of a system fault; part of a non-time delay shutdown circuit (customer connections)	Shutdown	Service as required; selection jumpers may choose warning only or 10 second time delay shutdown
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
HI FUEL	Day tank HI FUEL lamp	Fuel in the day tank has reached an abnormally high level, indicating possible failure of the pump-off float switch	Warning	High-fuel float switch takes over as automatic pump-off switch; reset when level drops to normal
High Engine Temperature (Red)	High Engine Temperature shutdown	Engine shut down because of excessively high engine coolant temperature (greater than 230 F)	Shutdown	Reset ECM; fill coolant as necessary and repair all leaks
LO FUEL	Day tank LO FUEL lamp	Fuel in the day tank has dropped to an abnormally low level, indicating possible failure of the pump-on float switch	Warning	Lo-fuel float switch takes over as automatic pump-on switch; reset when level rises to normal
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
LO SHUTDOWN	Day tank LO SHUTDOWN lamp	Fuel has dropped to a level near the bottom of the tank (empty main tank, pump failure, or float switch failure)	Shutdown	Check and fill main fuel tank; RESET both pump control and engine control
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
Low Engine Temperature (Yellow)	Low Engine Temperature (Detector-12)	Engine temperature is less than 70 F; possibility the engine might not start	Warning	Plug in, repair or install engine coolant and engine oil heaters
Low Fuel (Yellow)	Low Fuel (Detector-12)	Fuel level in the supply tank has dropped below reserve necessary for full load	Warning	Fill the main fuel supply tank with the appropriate grade of fuel
Low Oil Pressure (Red)	Low Oil Pressure shutdown	Engine shut down because of excessively low engine oil pressure (less than 14 psi)	Shutdown	Reset ECM (Stop then Reset); fill engine oil as necessary and repair all oil leaks
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
Overcrank (Red)	Overcrank shutdown	Engine shut down because it did not start during the timed cranking period (approximately 75 seconds, including two rest periods)	Shutdown	Reset control (Stop then Reset), then push Run or Remote
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
Overspeed (Red)	Overspeed shutdown	Engine shut down because of overspeed	Shutdown	Adjust cutout speed or replace overspeed module/switch; check governor and speed pickup
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
Pre High Engine Temperature (Yellow)	Pre High Engine Temperature	Engine coolant temperature is abnormally high (greater than 220 F)	Warning	Shut down the set if possible or disconnect non-critical loads; service engine cooling system
PRE LO OIL PRES	Pre-Low Oil Pressure	Yellow lamp; engine oil pressure marginally low, 20 psi (138 kPa) or less	Warning	Find and correct cause as soon as possible
Pre Low Oil Pressure (Yellow)	Pre Low Oil Pressure	Engine oil pressure is abnormally low (less than 20 psi)	Warning	Shut down the set if possible or disconnect non-critical loads; service the engine lubricating system
RUN	Run	Green lamp; comes on when both primary and secondary starter circuits are opened after unit starts	Info
Run (Green)	Run lamp	Generator set is running and the starter has been disconnected	Info
SWITCH OFF	Switch Off (Detector-12)	Flashing red lamp; generator set is not in automatic start operation mode	Info	Press Run/Stop/Remote switch to Run or Remote position
Switch-off (Flashing Red)	Switch-off (Detector-12)	Run/Stop/Remote switch is in the Stop position, preventing remote automatic operation	Info	Push the Run-Stop-Remote switch to Run or Remote

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

Procedures

Convert Day Tank Controller 240 VAC to 120 VAC adjustment

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

Day Tank Controller Conversion 240 VAC to 120 VAC adjustment

Remove the two jumpers between terminals TB1-6 and TB1-7 and connect one between TB1-5 and TB1-6 and the other between TB1-7 and TB1-8.
Move selector switch S103 on the control PCB to the up position for 120V.
On the control transformer, remove the two jumpers between terminals H2 and H3 and connect one between H1 and H3 and the other between H2 and H4.

Dip Adjustment adjustment

Turn the DIP pot clockwise to increase the voltage vs frequency slope for frequencies below the UFRO threshold.
Greater slope gives greater voltage roll off as frequency drops, easing large load pickup but increasing voltage dip.
Turn the pot fully counterclockwise to make the slope the same above and below the threshold frequency.

Dwell Adjustment adjustment

Turn the DWELL pot clockwise to increase dwell time (voltage recovery time when frequency dips below threshold).
Turn the DWELL pot fully counterclockwise to eliminate dwell.
With no dwell, voltage recovery follows engine speed recovery.

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.

Governor Adjustments (Type A Electric Governor) adjustment

Set selector switch S1 to OFF, S2 to appropriate model position.
Set pots initially: Gain 20%, I 20%, D 30%, Droop 0%.
Start set, adjust Speed pot for required frequency (60Hz=1800RPM or 50Hz=1500RPM) at operating temperature.
Disconnect load, turn Gain pot to 100% or until unstable, then back off until stable.
Adjust D and I pots similarly; readjust Speed if necessary.
Push throttle to minimum speed, release and observe overshoot (2-5 Hz acceptable); adjust I pot to reduce overshoot or hunting.

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.

Initial Start Setup adjustment

⚠ Selecting this menu resets all operating parameters to default values; perform only by technically qualified personnel.

Press RESET, MENU and PHASE SELECT simultaneously to invoke the Initial Start Setup menu.
Toggle the Standby/Prime option.
Select the correct generator set model, frequency and kW rating.
Select the correct nominal line-to-line output voltage.
Select DELTA or WYE.
Select SAVE to save changes; MAIN MENU is then displayed.

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.

Operating PowerCommand in Droop Mode adjustment

Set the no load speed and voltage at the desired level (bus must be de-energized or disconnect Bus PT module).
Apply 100% load and adjust KW load sharing gain for desired full load frequency; adjust KVAR load sharing gain for desired full load voltage.
Repeat the process for other generator sets in the system.
Test the system with all available load and verify approximately equal load sharing at no load and maximum load.

Over / Under Voltage Module Recalibration adjustment

Remove the two screws securing the top to the case and withdraw the top assembly.
Adjust the UNDER setpoint SET pot to 75 percent.
Apply single-phase, 60 Hertz, 104.25 VAC across terminals L and N.
Adjust pot R25 on the PC board until the relay trips (de-energizes).
Adjust the OVER setpoint SET pot to 125 percent.
Apply single-phase, 60 Hertz, 173.75 VAC across terminals L and N.
Adjust pot R26 on the PC board until the relay trips (energizes).
Repeat until no adjustments are necessary, then reassemble the module.

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
		AVR response jumper	A to C	For generator output 90 kW or less (SX440 and MX321)
		Auxiliary terminal board TB21	K1, K2, P2, P3, P4, S2, S1, A2, A1	A1 and A2 connect a VAR/power factor controller when paralleling with a utility; S1 and S2 connect a droop compensating CT when paralleling with a generator set or utility
		Day tank LO SHUTDOWN engine shutdown connection	TB1-14 to engine block ground; TB1-15 to TB2-16 on the ECM
		Fault relay K8/K9 (Dry Contact Module)	K8=Over Crank, Low Oil Pressure, High Engine Temperature, Low Coolant Level, Low Fuel Level; K9=Low Fuel Level, Rupture Basin	Contact ratings: 40A max carry/break N.O. 12V coil, 30A N.C. 12V coil, 20A N.O./10A N.C. 24V coil
		MX321 PMG-excited jumper positions	2-3, 4-5 and 6-7	These jumpers must be in these positions
		MX321 voltage regulator frequency jumper	3-2 for 50 Hz; 3-1 for 60 Hz
		SX440 voltage regulator frequency jumper	C-50 for 50 Hz; C-60 for 60 Hz
		TB3 (ECM alternative RUN/STOP/REMOTE connection)	TB3-1=REMOTE, TB3-2=RUN, TB3-3=STOP	Provides alternative direct connection to ECM for troubleshooting or customer connection
		Voltage trimmer R21	voltage regulator terminals 1 and 2	There must be a jumper between terminals 1 and 2 when voltage trimmer R21 is not used
	single phase	QSG-Series power distribution panel voltage selector switch S1 position	main output terminals	Rotary switch under lockable cover selects 120/240 VAC single phase
	single phase	Voltage regulator terminal 6	jumpered to terminal 8	When the generator is connected for single-phase output, terminal 6 is not connected to the isolation transformer
	three phase	QSG-Series power distribution panel voltage selector switch S1 position	main output terminals	Rotary switch selects 120/208 VAC three phase
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	single phase	Day tank fuel pump control power reconnection	move jumpers from TB1-6/TB1-7 to TB1-5/TB1-6 and TB1-7/TB1-8	Move selector switch S103 on the control PCB to the up position for 120 V (factory set for 240 V, S103 down)
120/208	3
120/240	1
127/220	3
139/240	3
220/380	3
220/480	3
230/400	3
24		Day tank fuel pump control logic power (two lead harness, no transformer)	TB1-19 to positive (+) 24 V starter motor solenoid; TB-20 to negative (-)	Provides 24 VDC for the control circuit
240	single phase	Day tank fuel pump control default factory connection	jumpers between terminals TB1-6 and TB1-7	Selector switch S103 on the control PCB in the down position for 240 V
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 6CT8.3 family

Part #	Description	Category
B-45	CHECKING BATTERY	Battery
FP-3911558	Belt, V Ribbed (Alternator)	Belt
FP-3911582	Belt, V Ribbed (Alternator)	Belt
2278784	Fuel pump-governor combination	Fuel filter
FP-3921978	Solenoid, Fuel Pump Shutoff (12 Volt)	Fuel pump
FP-3921980	Solenoid, Fuel Pump Shutoff (24 Volt)	Fuel pump
DM-3801373	Gasket Set - 6CT 8.3	Gasket
FP-3902089	Gasket, Water Pump Mounting	Gasket
FP-3914310	Gasket, Thermostat Housing	Gasket
FP-3918174	Gasket, Oil Cooler Core	Gasket
FP-3918332	Gasket, Oil Cooler Core Cover	Gasket
FP-3932063	Gasket, Exhaust Manifold	Gasket
FP-3935585	Gasket, Cylinder Head (Standard)(230 HP & Below)	Gasket
FP-3936993	Gasket, Intake Manifold Cover	Gasket
FP-6C83PREM	6C/6CT8.3 In-Frame Kit w/upper gasket set & oil pan gasket	Gasket
FP-IFK6C83PREM	6C/6CT8.3 In-Frame Kit w/upper gasket set & oil pan gasket	Gasket
DM-3928389	Fuel Injector - 6CT 8.3	Injector
LF3000	Lube, Spin-On	Oil filter
LS1174s	OIL FILTER	Oil filter
DM-3802010	Main Bearing Set Standard - 4BT 3.9, 6BT 5.9, 6CT 8.3	Service part / kit
DM-3802439	Piston Ring Set - 6CT 8.3	Service part / kit
FP-3356824	6C/6CT8.3 In-Frame Kit (contains FP-3802403 Cyl Kit)	Service part / kit
FP-3356825	6C/6CT8.3 In-Frame Kit (contains FP-3802404 Cyl Kit)	Service part / kit
FP-3356826	6C/6CT8.3 In-Frame Kit (contains FP-3802406 Cyl Kit)	Service part / kit
FP-3356827	6C/6CT8.3 In-Frame Kit (contains FP-LK92479937 Cyl Kit)	Service part / kit
FP-3357573	6C/6CT8.3 In-Frame Kit (contains FP-3802263 Piston Kit)	Service part / kit
FP-3357574	6C/6CT8.3 In-Frame Kit (contains FP-3802601 Piston Kit)	Service part / kit
FP-3357803	6C/6CT8.3 In-Frame Kit (contains FP-3802344 Piston Kit)	Service part / kit
FP-3923564	Guide, Valve Stem (Intake & Exhaust Valve)	Service part / kit
FP-3974815	Oil Cooler Core	Service part / kit
FP-3806180	Pump, Water	Pump
FP-3936321	Pump, Fuel Transfer	Pump
FP-3948071	Pump, Lubricating Oil	Pump
FP-4944710	Pump, Fuel Transfer	Pump
FP-3905449	Seal, Rocker Lever Cover	Seal
FP-3927642	Seal, Valve Stem (Intake & Exhaust Valve)	Seal
FP-3928639	Thermostat Assembly (83° C), (180° F)	Thermostat

Parts cataloged across all variants of this engine family — verify the exact part fits your specific variant and serial number before ordering.

Common questions

What is the oil capacity of the Cummins/Onan 6CT8.3?

The Cummins/Onan 6CT8.3 engine has an oil capacity of 19.0 liters.

What is the displacement of the Cummins/Onan 6CT8.3?

The Cummins/Onan 6CT8.3 has a displacement of 8.3 liters with 6 cylinders.

Which generators use the Cummins/Onan 6CT8.3 engine?

The Cummins/Onan 6CT8.3 powers 4 generator set(s), including AKSA AC 200, AKSA AC150, Cummins/Onan 6CT 8.3, Cummins/Onan DGEA.

How often should you change the oil in the Cummins/Onan 6CT8.3?

The Cummins/Onan 6CT8.3 oil change interval is every 2000 hours.

What is a common problem with the Cummins/Onan 6CT8.3 engine?

A commonly reported issue on generators using the Cummins/Onan 6CT8.3 is: Low Power. Cause: Vehicle Overloaded. Fix: Reduce load or use lower gears..