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Cummins/Onan KTA38G4 Engine

The Cummins/Onan KTA38G4 is a 37.8 L 12-cylinder turbo aftercooled engine rated at 1800 rpm. It powers generator sets from Cummins/Onan, including the 1020 DFJD, 928, CP1100-6 and CS1250-6. It holds 140 L (37.0 gal) of oil and 336.5 L (88.9 gal) of coolant.

Also known as: Cummins KTA38G4

37.8 L

Displacement

Cylinders

1800 rpm

Rated speed

140.0 L

Oil capacity

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

Engine specifications

Oil capacity	140.0 L
Coolant capacity	336.5 L
Displacement	37.8 L
Cylinders	12
Aspiration	Turbo Aftercooled
Rated speed	1800 rpm

Generator sets powered by this engine

Cummins/Onan 1020 DFJD Cummins/Onan 928Cummins/Onan CP1100-6Cummins/Onan CS1250-6 Cummins/Onan DFJD Cummins/Onan KTA38

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

Common problems

Engine fails to start, or starts, runs and then stops
Fix: Refer to Troubleshooting Section in the Operator’s manual

Compiled from service & troubleshooting documentation across every generator set that uses the Cummins/Onan KTA38G4.

Service intervals

Item	Action	Hours	Months	Notes
crankcase oil	Change	50 hr		First service — Drain and replace crankcase oil after the first 50 hours of operation on new generator sets; make a special entry in the unit log book.
Air cleaner element - restriction	Check	250 hr	6 mo	Replace air cleaner element as required
All belts	Check	250 hr	6 mo
Cooling fan	Check	250 hr	6 mo	Check for cracks, loose rivets, bent or loose blades
Engine oil	Change	250 hr	6 mo	Whichever occurs first
Fan idler pivot arm	Lubricate	250 hr	6 mo	Water pump type grease until grease appears
Front engine support	Lubricate	250 hr	6 mo	Chevron SRI grease or equivalent
Fuel filter	Replace	250 hr	6 mo
Hoses	Inspect	250 hr	6 mo	Check/replace as required
Oil filters	Change	250 hr	6 mo	Change filters with oil
Pulley tensioner	Check	250 hr	6 mo
Batteries	Check	1500 hr	12 mo
Cold start aids	Check	1500 hr	12 mo	Seasonal
Crankshaft end clearance	Inspect	1500 hr	12 mo
Engine (steam clean)	Clean	1500 hr	12 mo	Before conducting any 1500 hour maintenance
Engine mounting bolts and nuts	Check	1500 hr	12 mo	Tighten loose; inspect rubber
Engine protection system	Check	1500 hr	12 mo
Fan idler pulley tensioner	Adjust	1500 hr	12 mo
Heat exchanger zinc plugs (marine only)	Check	1500 hr	12 mo	Change if 50 percent eroded
Valves and injectors	Adjust	1500 hr	12 mo	First service — Initial adjustment at 1500 hours; thereafter not again before 6000 hour injector calibration
Air compressor	Inspect	6000 hr	24 mo	Discharge and intake checks
Coolant	Change	6000 hr	24 mo	Clean and flush cooling system
Crankcase breather element	Replace	6000 hr	24 mo	Clean/replace
Engine protection system	Adjust	6000 hr	24 mo	Calibrate
Fan hub	Inspect	6000 hr	24 mo	End clearance and grease leakage
Fan idler pulley assembly	Replace	6000 hr	24 mo	Rebuild or replace as necessary
Fuel pump	Clean	6000 hr	24 mo	Clean and calibrate
Injectors	Clean	6000 hr	24 mo	Clean and calibrate
Thermostats and seals	Replace	6000 hr	24 mo
Turbocharger	Inspect	6000 hr	24 mo
Vibration damper	Inspect	6000 hr	24 mo	Replace after 24,000 hours; K2000 dampers replaced every 12,000 hours
Water pump	Replace	6000 hr	24 mo	Rebuild or replace
Rupture basin leak detect switch	Test		12 mo	Check once a year; in some areas weekly inspections may be required by safety code regulations

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	Angular alignment maximum T.I.R.	0.001	inch per inch of radius (center of shaft to indicator axis)	measuring deflection to bolt heads
Clearance	Crankshaft end clearance	0.13 MIN / 0.51 MAX	mm
Clearance	Fan hub bearing end clearance	0.03 MIN / 0.15 MAX	mm
Clearance	Float switch assembly float lift clearance below C-clip stop	1/8	inch (3 mm)	use a feeler gauge
Clearance	Generator-to-engine angular alignment (T.I.R.)	.001 in. per inch of radius (center of shaft to indicator axis), maximum	in	750 kW gensets and larger
Clearance	Thermostat seal installation depth	no more than 0.51	mm	below top of cast edge
Clearance	Turbocharger BB (RR-151) and (RR-153) end clearance	0.09 MIN / 0.13 MAX	mm
Clearance	Turbocharger BB bearing radial clearance - RR-151	0.75 MAX	mm	0.030 in
Clearance	Turbocharger BB bearing radial clearance - RR-153	0.55 MAX	mm	0.021 in
Clearance	Turbocharger axial end play - HC5A	0.05 MIN / 0.13 MAX	mm
Clearance	Turbocharger axial end play - HT7100	0.06 MIN / 0.16 MAX	mm
Clearance	Turbocharger axial end play - T18A	0.10 MIN / 0.23 MAX	mm
Clearance	Turbocharger radial clearance compressor impeller - HC5A	0.15 MIN / 0.45 MAX	mm
Clearance	Turbocharger radial clearance turbine wheel - HC5A	0.20 MIN / 0.55 MAX	mm
Clearance	Vibration isolator top plate clearance	0.25	in (6 mm)	nominal
Gap	Heat exchanger zinc plug erosion limit A	approximately 19	mm	0.75 in; new 51 mm [2 in]
Gap	Heat exchanger zinc plug erosion limit B	approximately 6.4	mm	0.25 in; new 16 mm [0.625 in]
Gap	MPU sensor to flywheel ring gear tooth	back it out one quarter turn	turn	sensor threaded in until it just touches gear tooth
Other	AVR Droop setting	5	% at full load, 0 PF
Other	AVR voltage regulation (load regulation)	approximately ±0.5	% RMS
Other	Air compressor discharge carbon deposit thickness limit	2	mm	1/16 in
Other	Alternator belt tension	356	N	80 lbf, Burroughs tension gauge GT-1293
Other	Angular alignment maximum T.I.R.	.001 inches per inch of radius	in/in	center of shaft to indicator axis
Other	Battery specific gravity (high ambient, above 95F/35C)	1.225		recommended to reduce electrolyte loss
Other	Battery specific gravity (recharge threshold)	below 1.260
Other	Battery specific gravity, fully charged	approximately 1.260	specific gravity	at 80 F (27 C)
Other	Fuel lift height limit	6	feet	(1.8 meters) between fuel lift pump and bottom of dip tube
Other	GOV GAIN default value for paralleling applications	70	%
Other	Maximum angular alignment T.I.R.	0.001	in per inch of radius (center of shaft to indicator axis)
Other	Maximum cranking voltage drop	2	volts	difference between battery and starter terminals while cranking
Other	Maximum vibration damper thickness - Houdaille	66.38	mm	2.574 in
Other	Maximum vibration damper thickness - Made in England Before F-82	65.91	mm	2.595 in
Other	Maximum vibration damper thickness - Made in England F-82 and After	65.66	mm	2.585 in
Other	Over/Under Frequency Sensor Module - Over Hz Set, 50 Hz nominal	55	Hz	reset 53 Hz
Other	Over/Under Frequency Sensor Module - Over Hz Set, 60 Hz nominal	65	Hz	reset 63 Hz
Other	Over/Under Frequency Sensor Module - Under Hz Set, 50 Hz nominal	45	Hz	reset 47 Hz
Other	Over/Under Frequency Sensor Module - Under Hz Set, 60 Hz nominal	55	Hz	reset 57 Hz
Other	Over/Under Voltage Sensor Module time delay	typically 25 percent, approximately 2.5	seconds
Other	Overcrank cranking limit	75	seconds	three 15-second cranking cycles with two 15-second rest periods
Other	PTD injector travel verification specification	7.80 MIN / 7.82 MAX	mm
Other	PTD non-top stop injector travel adjustment	7.82	mm
Other	PTD non-top stop injector travel limits	7.77 to 7.87	mm
Other	REG VHZ (underfrequency roll-off) adjustable range	1 through 50; normal range 7 through 21
Other	Start delay adjustment range	0 to 300	seconds
Other	Stop delay adjustment range	0 to 600	seconds
Other	Two pulley fan drive belt tension (set)	2668.9 to 2891.3	N	600 to 650 lbf
Other	Two pulley fan drive belt tension (verify)	2891.3 to 3336.2	N	650 to 750 lbf
Other	Under Frequency Roll Off (UFRO) knee point, 50 Hz units	48 to 49	Hz
Other	Under Frequency Roll Off (UFRO) knee point, 60 Hz units	58 to 59	Hz
Other	Under-frequency roll-off threshold (UFRO)	typically 59 Hz for 60 Hz applications and 49 Hz for 50 Hz applications	Hz	AVR UFRO pot preset
Other	Vibration damper thickness variation (four readings 90 degrees apart)	must not vary more than 0.25	mm	0.010 in
Pressure	Coolant pressure cap minimum	50	kPa	7 psi
Pressure	Engine oil pressure - K19 normal	50-70	psi (345-482 kPa)	run mode
Pressure	Engine oil pressure - K38 normal	45-65	psi (310-448 kPa)	run mode
Pressure	Engine oil pressure - K50 normal	50-70	psi (345-482 kPa)	run mode
Pressure	Engine oil pressure - L10/M11 normal	30-50	psi (207-345 kPa)	run mode
Pressure	Engine oil pressure - NTA 855 normal	35-50	psi (241-345 kPa)	run mode
Pressure	Engine oil pressure - V28 normal	50-90	psi (345-620 kPa)	run mode
Pressure	Engine oil pressure gauge	40 to 70	psi (275 to 483 kPa)	engine at operating temperature
Pressure	Engine oil pressure shutdown limit - L10/M11	20	psi (138 kPa)	run mode value

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	50/50 low-silicate antifreeze and quality water	ASTM D4985 (less than 0.10% silicate as Na2SiO5)			Must be pre-charged with supplemental coolant additives (DCA4) to 1.5 units per gallon; never below 1.2 or above 3 units per gallon. Do not use soluble oils.
Coolant	Ethylene glycol based permanent antifreeze				Precharged spin-on corrosion filters compatible with plain water and all ethylene glycol based permanent antifreeze coolants. Remote radiator requires a deareation type radiator or separate auxiliary tank with capacity at least 5% of total coolant volume.
Coolant	soft water / E.G. / DCA mixture				Cooling system to be filled with soft water/E.G./DCA mixture (on-site review checklist).
Engine oil	SAE 15W-40	API CE or CF4 (CD or CD/SF where CE/CF4 not available)			Multigrade preferred; sulfated ash limit must not exceed 1.85 mass percent. Arctic operation (below -23 C) use synthetic CE/SF 5W-30.
Fuel	ASTM No. 2 Diesel				Check the engine manual for fuel specifications to determine acceptability. Do not use galvanized fuel lines, fittings or tanks; do not use copper tubing for fuel lines.
Fuel	ASTM No. 2 diesel				Below 0 C use blends of No. 2D and No. 1D. Viscosity must be kept above 1.3 cSt. Do NOT mix gasoline or alcohol with diesel fuel.
Fuel	Diesel				Day tank fuel transfer pump maintains reservoir of diesel fuel in the day tank.
Grease	Lithium based grease	Mobilux No. 2 or Shell Alvania R3		2.74 oz (81 ml)	Generator end bearing. Temperature range -22F to +248F (-30C to +120C). Grease should be equally divided between the bearing, bearing cap cavity, and bearing cartridge cavity.
Grease	Water pump type grease (Amoco Rykon Premium No. 2 / Chevron SRI / Exxon Unirex N2 / Shell Dolium R / Texaco Premium RB)				Fan idler pivot arm and front engine support lubrication
Grease	Lithium based grease, Mobilux No. 2 or Shell Alvania R3		-30°C to 120°C	2.74 oz (81 ml)	End bearing lubricant; grease equally divided between bearing, bearing cap cavity and bearing cartridge cavity.

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 causes generator build-up to be inhibited and the engine to be governed at 800 RPM.	Warning	Remove ground from engine idle input to return to normal speed and voltage.
102	EMERGENCY STOP	Indicates local or remote Emergency Stop.	Shutdown	Turn the switch clockwise and allow it to pop out (local only); move the Run/Off/Auto switch to Off; press the Reset switch; select Run or Auto as required. Can be reset only at the PCC front panel.
200	LOW OIL PRESSURE	Indicates engine oil pressure has dropped to an unacceptable level.	Warning	If generator is powering critical loads and cannot be shut down, wait until next shutdown period and then follow 201-SHUTDOWN procedure. Access 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; replenish if low; reset control and restart.
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°F (21°C) or lower.	Warning	Indicates engine coolant heater is not operating or is not circulating coolant. Check coolant heater power supply, low coolant level, and heater element current draw.
211	HIGH COOLANT TEMP	Indicates the engine coolant temperature is getting close to the recommended maximum temperature limit: 215° F (102° C) − standby or 207° F (97° C) − primary.	Warning	Reduce load if possible; check air inlets and outlets and remove obstructions to airflow.
212	HIGH COOLANT TEMP	Indicates engine has overheated (coolant temperature has risen above the shutdown trip point: 215 F (102 C) - standby or 207 F (97 C) - primary).	Shutdown	Check for obstructions to cooling airflow; check fan belt; check coolant mixture; check blower fan and circulation pumps; reset control and restart.
213	COOLANT SENDER	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	Check coolant level in radiator and coolant recovery bottle; replenish if low; look for leaks.
215	LOW COOLANT LVL	Indicates engine coolant level has fallen below the trip point.	Shutdown	Allow engine to cool; check coolant level and leakage points; reset control and restart.
220	MAG PICKUP	Mag pickup speed indication is not being sensed or does not match generator set output frequency.	Shutdown	Restart and check RPM; check PCC model setting; inspect and test MPU.
221	FAIL TO CRANK	Possible fault with control or starting system.	Shutdown	Check fuse F3 on the Engine Interface board; check battery cable connections; recharge or replace the battery.
222	OVERCRANK	Possible fuel system problem.	Shutdown	Check for empty fuel tank, leaks, plugged fuel lines; replace dirty fuel or air filter; reset and restart.
223	OVERSPEED	Indicates engine has exceeded normal operating speed. (115% ±1% of nominal).	Shutdown	Check mechanical fuel linkage and governor module/digital board duty cycle.
224	FAIL TO SYNCHRONIZE	Generator set has not synchronized to the system bus within the allowable time frame.	Warning	Check governor system stability; adjust governing and synchronizer parameters; check fuel system.
226	FAIL TO CLOSE	Paralleling breaker has been given a signal to close, but has not closed properly.	Shutdown	Verify breaker charging mechanism; check close signal; verify auxiliary contact signals.
230	LOW DC VOLTAGE	Indicates battery voltage is below 10 VDC.	Warning	Recharge or replace the battery; check the battery charger fuse. Clean and tighten battery cable connections. Check engine DC alternator; replace if normal charging voltage is not obtained. Check float level if applicable.
231	HIGH DC VOLTAGE	Indicates battery voltage exceeds 32 VDC.	Warning	Lower battery charger float level if applicable; check engine DC alternator.
232	WEAK BATTERY	Indicates battery voltage drops below 60% of nominal for two seconds, during starting.	Warning	See LOW DC VOLTAGE 230.
240	LOW FUEL−DAY	Indicates day tank fuel supply is running low.	Warning	Check fuel supply and replenish as required.
241	LOW FUEL	Low fuel signal received.	Warning	Check fuel supply and replenish; check for short to ground in external wiring.
250	EEPROM ERROR	PCC memory error; data corruption of critical operating parameters.	Shutdown	Perform the initial start setup procedure; if the set shuts down on the same EEPROM ERROR message, replace the digital board (A32).
251	EEPROM ERROR	PCC memory error; data corruption of noncritical operating parameters.	Warning	Perform the adjustment procedures; if the same message occurs, perform calibration procedures; if the message persists, replace the digital board (A32).
252	EEPROM ERROR	PCC memory error; data corruption of noncritical operating parameters.	Warning	Verify values/choices selected and repeat the save operation; if the same message occurs, replace the digital board (A32).
260	CUSTOMER FAULT 1	When this customer defined input is closed to ground, the corresponding fault message is displayed. Programmable to initiate a shutdown or a warning.	Warning	Isolate source of false signal; repair external wiring or replace A34.
261	GROUND FAULT	When a customer defined input is closed to ground, the corresponding fault message is displayed. Default message; editable for customer site requirements.	Warning	Isolate source of false signal; repair external wiring or replace A34.
262	RUPTURE BASIN	When a customer defined input is closed to ground, the corresponding fault message is displayed. Default message; editable for customer site requirements.	Warning	Isolate source of false signal; repair external wiring or replace A34.
263	HIGH GEN TEMP	When a customer defined input is closed to ground, the corresponding fault message is displayed. Default message; editable for customer site requirements.	Warning	Isolate source of false signal; repair external wiring or replace A34.
270	PHASE ROTATION	The phase relationship between the generator set and the system bus is not matched.	Shutdown	Verify genset phase rotation matches bus; verify control wiring to bus PT module.
272	FIRST START	PowerCommand control is not receiving a proper signal from the system master first start sensor.	Warning	Verify Master First Start Sensor and interconnection wiring.
301	HIGH AC VOLTAGE	One or more phase voltages exceeded 130% of nominal, or exceeded 110% of nominal for 10 seconds.	Shutdown	Set display to GEN, VOLTS, L-N; determine if the output voltage the control sees is low or high; isolate PCC/alternator/excitation circuit.
303	LOW AC VOLTAGE	One or more phase voltages dropped below 85% of nominal for 10 seconds.	Shutdown	Check PMG/field wiring, rotating rectifier, load and connectors.
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.
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 that 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	Three-phase power output exceeds 105% of standby (or 115% of prime) rating.	Warning	Check load and load lead connections.
335	REVERSE POWER	Power is flowing into the generator set rather than out from the unit.	Shutdown	Verify CT connections, load sharing lines, and generator set frequency/voltage.
337	LOSS OF EXCITATION	Alternator excitation system is improperly adjusted or has failed.	Shutdown	Check output voltage calibration, load sharing lines, and leading power factor loads.
FAULT 1	Fault 1 (Red)	Undedicated customer-defined fault; may be programmed as timed or non-timed shutdown or fault light only.	Shutdown	Service as required by the customer-supplied fault indicating switches.
FAULT 2	Fault 2 (Red)	Undedicated customer-defined fault, same features as Fault 1.	Shutdown	Service as required by the customer-supplied fault indicating switches.
GF	Ground Fault Alarm (Optional)	Ground fault relay monitors neutral to ground connection and line to neutral, activating a fault alarm when the connection is broken or a ground fault is sensed.	Warning	Clear fault condition by pushing the Run/Stop (Reset)/Remote switch to Reset (auto reset link set at factory).
HET	High Engine Temperature (Red)	Engine shut down because of excessively high engine coolant temperature (greater than 230 deg F).	Shutdown	Check coolant level and leaks; service cooling system; reset engine control.
HI ENG TEMP	High Engine Temperature	Engine shut down due to critically high coolant temperature (above 215F/102C).	Shutdown
LET	Low Engine Temperature (Yellow)	Engine temperature is less than 70 deg F and the engine might not start.	Warning	Plug in, repair or install engine coolant and oil heaters.
LO FUEL	Low Fuel	Fuel supply is marginally low, if equipped (Detector-12).	Warning
LO OIL PRES	Low Oil Pressure	Engine shut down due to critically low oil pressure (below 14 psi/97 kPa).	Shutdown
LOP	Low Oil Pressure (Red)	Engine shut down because of excessively low engine oil pressure (less than 14 psi).	Shutdown	Check oil level and oil leaks; service lubricating system; reset engine control.
LOW ENG TEMP	Low Engine Temperature	Engine water jacket temperature is 70F/21C or lower; indicates possible inoperative coolant heater (Detector-12).	Warning
LOW FUEL	Low Fuel (Yellow)	Fuel level in the supply tank has dropped below the reserve necessary to run the set at full load for the prescribed number of hours.	Warning	Fill the main fuel supply tank with the appropriate grade of fuel.
OC	Overcrank (Red)	Engine shut down because it did not start during the timed cranking period (approximately 75 seconds, including two rest periods).	Shutdown	Service the set as necessary; reset engine control.
OS	Overspeed (Red)	Engine shut down because of overspeed.	Shutdown	Adjust the Electronic Overspeed Module; check governor for binding; reset engine control.
OVERCRANK	Overcrank	Starter locked out because of excessive cranking time (limited to 75 seconds).	Shutdown
OVERSPEED	Overspeed	Engine shut down because of excessive speed.	Shutdown
PRE HI ENG TEMP	Pre-High Engine Temperature	Coolant temperature is marginally high (205F/97C or higher).	Warning	Attend to when generator set is shut down.
PRE LO OIL PRES	Pre-Low Oil Pressure	Engine oil pressure is marginally low (20 psi/138 kPa or less).	Warning	Attend to when generator set is shut down.
PRE-HET	Pre High Engine Temperature (Yellow)	Engine coolant temperature is abnormally high (greater than 220 deg F).	Warning	Shut down if possible or disconnect non-critical loads; service cooling system.
PRE-LOP	Pre Low Oil Pressure (Yellow)	Engine oil pressure is abnormally low (less than 20 psi).	Warning	Shut down if possible or disconnect non-critical loads; service lubricating system.
RUN	Run (Green)	Green lamp comes on when both primary and secondary starter circuits open after unit starts.	Info
SWITCH OFF	Switch-off (Flashing Red)	The Run/Stop/Remote switch is in the Stop position, preventing remote automatic operation.	Info	Push the Run-Stop-Remote switch to 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

Aligning Generator with Engine (Angular Alignment) adjustment

⚠ Accidental starting of the generator set during this procedure presents the hazard of severe personal injury or death.

Tools: Dial indicator, Shims

Disconnect the negative (-) battery cable(s) before beginning.
Fasten a dial indicator to the generator shaft or cooling fan with the sensing point on the capscrew head or flat surface of the drive disc at the bolt circle diameter.
Bar the engine over in a clockwise rotation as viewed from engine flywheel; do not allow it to roll back on compression.
Determine the total indicator reading (T.I.R.) as the sum of the maximum positive and negative dial indicator readings over one revolution.
Measure the distance from the center of the generator shaft to the indicator measuring point.
Measure the distance from the generator side of the flex discs to the center of the generator mounting bolt.
Compare the distances; multiply this ratio times one half the T.I.R. to approximate the amount of shims to remove or add.

Alternator Belt Adjustment adjustment

⚠ Over-tensioning of alternator belts can result in premature accessory drive bushing wear and seal leakage.

Tools: GT-1293 Burroughs Tension Gauge

Loosen the alternator and adjusting link mounting capscrews.
Loosen the jam nuts on the adjusting screw.
Turn the adjusting screw clockwise to tighten the belt tension.
Check the belt tension with a gauge.
Tighten the jam nuts on the adjusting screw to 55 Nm [40 ft-lb].
Tighten the adjusting link and alternator mounting capscrews to 55 Nm [40 ft-lb].
Check the belt tension again.

Angular Alignment Procedure adjustment

⚠ Accidental starting of the generator set during this procedure presents the hazard of severe personal injury or death. Make sure to disconnect the negative (-) battery cable(s) before beginning.

Tools: Dial indicator, Wooden shims

Disconnect the negative (-) battery cable(s) before beginning.
Fasten a dial indicator to the generator shaft or cooling fan with sensing point on capscrew head or flat surface of drive disc at bolt circle diameter.
Bar the engine over in a clockwise rotation as viewed from engine flywheel; do not allow it to roll back on compression.
Record maximum positive and negative dial indicator readings as the engine completes one revolution.
T.I.R. equals the sum of the maximum positive and negative readings.
Maximum T.I.R. should not be more than .001 inch for each inch of radius.
Remove equal shims from under both generator mounting feet to lower the generator.

Angular Alignment Procedure (Generator to Engine) adjustment

⚠ Accidental starting during this procedure presents the hazard of severe personal injury or death.

⚠ Do not bar engine over by prying on fan blade.

Tools: dial indicator

Disconnect the negative (-) battery cable(s) before beginning.
Fasten a dial indicator to the generator shaft or cooling fan with sensing point resting on the drive disc capscrew head/flat surface at the bolt circle diameter.
Bar the engine over in a clockwise rotation as viewed from the engine flywheel; do not allow it to roll back on compression at the end of travel of each reading.
Record the total indicator reading (T.I.R.) as the sum of the maximum positive and negative dial indicator readings over one engine revolution.
Compare the measured T.I.R. to the maximum allowed (.001 in. per inch of radius from center of shaft to indicator axis); add or remove shims under the generator mounting feet to correct.

Axial Alignment Procedure adjustment

Tools: Dial indicator with magnetic base or clamp, Torque wrench

Check axial misalignment only when an objectionable vibration is present.
Fasten dial indicator holding device to skid base, engine block, or generator shell with a magnetic base or clamp; position sensor on the generator shaft hub.
Bar the engine over in a clockwise rotation as viewed from the engine flywheel through a couple of rotations.
Record indicator readings in eight equally spaced points around the shaft diameter to obtain T.I.R.
Reduce the measured T.I.R. runout by one half.
To correct, remove capscrews connecting drive discs and flywheel and mark the discs and flywheel with respect to each other.
Rotate either the engine or generator so drive disc holes are repositioned 180 degrees from original location; reinstall capscrews and retorque; recheck alignment.
If runout remains unchanged, rotate discs to 30, 60 or 90 degrees from original location.
If T.I.R. does not improve after repositioning, inspect flywheel pilot and drive disc runouts.

Axial Alignment Procedure (Generator to Engine) adjustment

Tools: dial indicator

Fasten a dial indicator holding device to the skid base, engine block, or generator shell with the sensor point resting on the generator shaft hub.
Bar the engine over in a clockwise rotation through a couple of rotations, recording indicator readings at eight equally spaced points around the shaft diameter to obtain axial T.I.R.
Reduce the measured T.I.R. runout by one half if excessive vibration remains after angular alignment.

Crossheads - Adjustment adjustment

Tools: ST-669 Torque Wrench Adapter

Adjust the crossheads on the cylinder that has both valves closed.
Loosen the crosshead adjusting screw locknuts on the intake and exhaust valve crossheads.
Turn the adjusting screw out at least one turn.
Hold the crosshead down against its guide.
Turn the adjusting screw in until it touches the top of the valve stem but does not raise the crosshead.
Hold the adjusting screw and tighten the lock nut to the torque value.

Dipstick Calibration adjustment

⚠ The dipstick will break if the scribe mark is too deep.

Tools: scribe

Drain the oil from the pan.
Install the dipstick in the dipstick tube.
Use clean 15W-40 oil to fill the oil pan to the specified low level.
Remove the dipstick and scribe a mark across the dipstick at the oil level. Mark the low level with an L.
Install the dipstick and add additional oil to the specified full level.
Remove the dipstick and scribe a mark across the dipstick at the oil level. Mark the high oil level with an H.

Governor Calibration Checks adjustment

Tools: Frequency meter or tachometer, Jumper wire

Start the generator set.
Adjust engine no-load speed to the desired allowable speed droop using the Run Speed potentiometer.
With no load, turn GAIN clockwise slowly until engine speed oscillates.
Reduce GAIN slowly counterclockwise until engine speed is stable.
Upset the governor by momentarily shorting terminals 7 and 10 on the governor control.
Apply and remove loads to check generator set response.

HC4-7 Axial Alignment Procedure adjustment

Tools: Dial indicator with magnetic base or clamp

Check only when an objectionable vibration is present.
Fasten dial indicator holding device to skid base, engine block, or generator shell with magnetic base or clamp.
Position sensor point on the generator shaft hub.
Bar the engine over in a clockwise rotation as viewed from engine flywheel through a couple of rotations.
Record indicator readings in eight equally spaced points around the shaft diameter.
Remove the capscrews connecting drive discs and flywheel and mark discs and flywheel.
Rotate engine or generator so drive disc holes are repositioned 180 degrees from original location.
Put capscrews back in and retorque. Recheck shaft alignment.
If runout unchanged, rotate discs to 30, 60 or 90 degrees from original location.
If T.I.R. does not improve, inspect flywheel pilot and drive disc runouts.

P7 Axial Alignment Procedure adjustment

Check only when an objectionable vibration is present.
Remove the capscrews connecting drive discs and flywheel.
Mark the drive discs and flywheel with respect to each other.
Rotate engine or generator so drive discs holes are repositioned two bolt holes from original location.
Put capscrews back in and retorque. Recheck/record vibration levels.
Repeat this test until drive disc holes are repositioned 180 degrees from original location.
Review vibration data and position drive disc in lowest recorded level location.

PT (type D) Injector - Adjustment adjustment

⚠ The injector plunger is under spring tension. Do NOT allow the tool to slip.

⚠ Prevent damage to the indicator by allowing the lever to return slowly.

Tools: 3822575 injector and valve adjustment kit, 3822574 rocker lever actuator, ST-669 Torque Wrench Adapter

Assemble the parts of an injector and valve adjustment kit, Part No. 3822575, or equivalent, and install it on the cylinder.
Adjust the indicator so the tip touches the top of the injector plunger.
Lower the indicator 12.25 mm [0.5 inch] to allow for travel. Lock the indicator support to the post.
Use a rocker lever actuator, Part No. 3822574, or equivalent. Depress the lever until the injector bottoms two or three times.
Hold the lever with the injector plunger firmly bottomed and set the indicator to ZERO.
Turn the adjusting screw until the indicator reads the specified travel.
Tighten the locknut to the torque value.
Check the injector adjustment and repeat if not within specification.

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
		12 lead generator sets	Load wires are routed through the CTs	Reconnectable gensets (12 leads) have dual secondary CTs (3 pins); CT wire 2/3 to pin 2 (high voltage) or pin 3 (low voltage).
		6 lead generator sets	Generator output leads are routed through the CTs	Non-reconnectable gensets (6 leads) have single secondary CTs (2 pins).
		Cummins PowerCommand generic AC Reconnect Wiring Diagram 625-2755 (Rev. D) and 625-3100 (Rev. F)		Applies to models DFAA, DFAB, DFAC, DFBF, DFCB, DFCC, DFEB, DFEC, DFFB, DFGA, DFGB, DFJA, DFJB, DFJC, DFJD, DFLB, DFLC, DFLD, DFMB (625-2755) and models DFAA-DFMB plus DFCE, DFED, DQAA, DQAB, DQBA, DQBB (625-3100).
	A (U)	CT21	U load leads (A phase)	CT dot must face the generator; CT terminal 1 connects to metering circuit, terminal 2/3 to ground.
	B (V)	CT22	V load leads (B phase)	CT dot must face the generator; terminal 1 to metering circuit, terminal 2/3 to ground.
	C (W)	CT23	W load leads (C phase)	CT dot must face the generator; terminal 1 to metering circuit, terminal 2/3 to ground.
110/190, 115/200	3	Code 31		Reconnectible stator
120/208	3	Code 4	4	60 Hz
120/208, 127/220	3	Code 519		Reconnectible stator
120/240	3	Code 5D	4	60 Hz
127/220	3	Code 8	4	60 Hz
139/240	3	Code $ (99 on nameplate)	4	No Standard Voltage Code, number 99 is marked on the nameplate for reference information
200/346	3	Code 523		Reconnectible stator
220/380	3	Code 7	4	60 Hz
220/380, 230/400	3	Code 520		Reconnectible stator
240/416	3	Code 7X	4	60 Hz
240/416, 254/440	3	Code 521		Reconnectible stator
240/416, 254/440	3	Code 522		Reconnectible stator
240/480	3	Code 6D	4	60 Hz
277/480	3	Code 4X	4	60 Hz
347/600	3	Code 9X	4	60 Hz

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

Common questions

What is the oil capacity of the Cummins/Onan KTA38G4?

The Cummins/Onan KTA38G4 engine has an oil capacity of 140.0 liters.

What is the displacement of the Cummins/Onan KTA38G4?

The Cummins/Onan KTA38G4 has a displacement of 37.8 liters with 12 cylinders.

Which generators use the Cummins/Onan KTA38G4 engine?

The Cummins/Onan KTA38G4 powers 6 generator set(s), including Cummins/Onan 1020 DFJD, Cummins/Onan 928, Cummins/Onan CP1100-6, Cummins/Onan CS1250-6, Cummins/Onan DFJD.

What is a common problem with the Cummins/Onan KTA38G4 engine?

A commonly reported issue on generators using the Cummins/Onan KTA38G4 is: Engine fails to start, or starts, runs and then stops. Fix: Refer to Troubleshooting Section in the Operator’s manual.