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Cummins/Onan KTA38G4 Engine

Name: Cummins/Onan KTA38G4 Engine
Brand: Cummins/Onan

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 →

Service intervals

Item	Action	Hours	Months	Notes
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

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

Service specifications

Type	Item	Value	Unit	Condition
Clearance	Crankshaft end 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
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]
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	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	GOV GAIN default value for paralleling applications	70	%
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	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 shutdown limit - L10/M11	20	psi (138 kPa)	run mode value
Pressure	Engine oil pressure shutdown limit - L10/M11	8	psi (55 kPa)	idle mode value
Pressure	Engine oil pressure warning limit - L10/M11	12	psi (83 kPa)	idle mode value
Pressure	Engine oil pressure warning limit - L10/M11	25	psi (172 kPa)	run mode value
Pressure	Exhaust back pressure maximum	75	mm Hg	3 in Hg, at rated speed and load
Pressure	K19 engine idle oil pressure	20	psi (138 kPa)	idle
Pressure	K19 engine normal oil pressure	50-70	psi (345-482 kPa)	normal run
Pressure	K19 oil pressure shutdown/warning limits	shutdown 35 psi (241 kPa) run; warning 40 psi (276 kPa) run; shutdown 10 psi (69 kPa) idle; warning 15 psi (103 kPa) idle	psi (kPa)
Pressure	K38 engine idle oil pressure	20	psi (138 kPa)	idle
Pressure	K38 engine normal oil pressure	45-65	psi (310-448 kPa)	normal run
Pressure	K38 oil pressure shutdown/warning limits	shutdown 35 psi (241 kPa) run; warning 40 psi (276 kPa) run; shutdown 10 psi (69 kPa) idle; warning 15 psi (103 kPa) idle	psi (kPa)

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	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				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	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.
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 above 215° F (102° C) − standby or 207° F (97° C) − primary).	Shutdown	Allow engine to cool; check airflow, fan belt, coolant mixture, blower fan and circulation pumps.
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 for poor battery cable connections; clean battery cable terminals and tighten. Recharge or replace a discharged or defective 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 actuator; check governor output module (A38) and digital board (A32).
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 initial start setup procedure; replace digital board (A32) if fault repeats.
251	EEPROM ERROR	PCC memory error; data corruption of noncritical operating parameters.	Warning	Perform adjustment and calibration procedures; replace digital board (A32) if fault repeats.
252	EEPROM ERROR	PCC memory error; data corruption of noncritical operating parameters.	Warning	Verify selected values; repeat save operation; replace digital board (A32) if fault repeats.
260	CUSTOMER FAULT 1	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.
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	Check PCC, alternator, excitation circuit, and PT/CT module wiring.
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	Undedicated customer-defined fault; may be programmed as timed or non-timed shutdown or fault light only.
FAULT 2	Fault 2	Undedicated customer-defined fault, same features as Fault 1.
HI ENG TEMP	High Engine Temperature	Engine shut down due to critically high coolant temperature (above 215F/102C).	Shutdown
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
LOW ENG TEMP	Low Engine Temperature	Engine water jacket temperature is 70F/21C or lower; indicates possible inoperative coolant heater (Detector-12).	Warning
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.
RUN	Run	Green lamp comes on when both primary and secondary starter circuits open after unit starts.	Info
SWITCH OFF	Switch Off	Generator set is not in automatic start operation mode (flashing red).	Info

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 (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 (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.

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.

Valves - Adjustment adjustment

⚠ Use the correct chart for the engine being serviced or the parts will be damaged.

Tools: 3376592 Inch Pound Torque Wrench, ST-669 Torque Wrench Adapter, feeler gauge

Select a feeler gauge for the correct valve lash specification and insert the gauge between the rocker lever and the crosshead.
Torque wrench method: use Part No. 3376592 inch pound torque wrench and tighten the adjusting screw to 0.68 Nm [6 in-lb].
Feel method: use a screwdriver and turn the adjusting screw only until the lever touches the feeler gauge.
The adjusting screw must not turn when the locknut is tightened.
Tighten the locknut to the value indicated.
The feeler gauge must slide backward and forward with only a slight drag.
Attempt to insert a feeler gauge 0.03 mm [0.001 in] thicker; the lash is not correct when the thicker gauge will fit.
Repeat until clearance is correct on both intake and exhaust valves.

Generator/PCC Control Isolation Procedure diagnostic

⚠ HIGH VOLTAGE. Touching uninsulated high voltage parts inside the control box can result in severe personal injury or death.

Tools: Voltmeter, Jumpers, 12 volt battery

Throw the line circuit breaker OFF and shut down the set.
Remove accessory box cover; remove plug P10 from A37 J10.
Prepare to measure output voltage across generator terminals.
Connect 12V battery jumpers to X (P10-6 red) and XX (P10-3 brown).
Check polarity; incorrect polarity makes the test inconclusive.
Start set and connect battery negative to the XX lead.
Rated or higher balanced voltage means generator circuitry is OK.
Unbalanced voltage: troubleshoot main stator; low voltage: exciter/field.

Insulation Resistance (Megger) & Polarization Index (PI) Testing diagnostic

⚠ The windings of medium-voltage (601 through 15,000 volts) generator sets must be dry before the generator is operated.

Tools: Megger or insulation resistance meter, Grounding cluster, High voltage gloves

Perform the Generator Set Grounding Procedure.
Disconnect plug J10 from A37 and AC control leads 4,5,6,7,8.
If RTD option installed, ground all six RTD temperature leads (18 leads).
Perform Insulation Resistance Test and PI Test for desired windings.
Megger test: apply voltage for up to one minute.
PI test: apply voltage for ten minutes; record 1-minute and 10-minute readings.
PI ratio of 2 or greater is good for new and in-service sets.
Investigate and correct low readings before returning set to service.

Megger and PI Test diagnostic

⚠ Medium-voltage (601 to 15,000 volts) windings must be dry before the generator is operated.

Tools: Megger or Insulation Resistance Meter, Wheatstone bridge or digital ohmmeter, Grounding Cluster

Perform the Generator Set Grounding Procedure.
Disconnect plug J10 from the voltage regulator output module and the AC control leads (marked 4, 5, 6, 7, 8).
If RTD option installed, ground all six RTD temperature leads (18 leads total).
Perform the Winding Resistance Test for the desired windings.
Perform the Insulation Resistance (Megger) Test and PI Test for the desired windings.
Megger test: apply voltage for up to one minute.
PI test: apply voltage for ten minutes; record resistance at one minute and ten minutes.
PI is the ten-minute reading divided by the one-minute reading; ratio of two or greater is good.

Testing Diodes diagnostic

⚠ Layers of dust can cause diodes to overheat and fail. Brush dust off regularly.

Tools: Ohmmeter

Disconnect the diode pigtails from the terminal posts.
Using an ohmmeter, measure resistance between pigtail and mounting plate.
Reverse meter test probes and repeat the tests.
Resistance should be high in one direction and low in the other.
If high or low in both directions, replace the diode.

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.