HomeEnginesCummins/Onan KTA-38-GI

Cummins/Onan KTA-38-GI Engine

The Cummins/Onan KTA-38-GI is an engine rated at 1800 rpm. It powers generator sets from Cummins/Onan, including the 750 DFZ. It holds 129 L (34.1 gal) of oil and 208 L (54.9 gal) of coolant.

Also known as: Cummins KTA-38-GI

Part of the Cummins/Onan KTA-38 engine family — 3 variants share parts & fitment.

1800 rpm
Rated speed
129.0 L
Oil capacity

Engine specifications

Oil capacity129.0 L
Coolant capacity208.0 L
Rated speed1800 rpm

Common problems

15
  • Starter has been locked out because of excessive cranking time. OVERCRANK
  • Same features as Fault 1 (normally set for timed shutdown). FAULT 2
  • PRE LO OIL PRES lamp lights. Engine continues to operate.
    Fix: Indicates engine oil pressure has dropped to 20 psi (138 kPa). If generator is powering critical loads and cannot
  • PRE HI ENGINE TEMP lamp lights. Engine continues to operate.
    Fix: Indicates engine has begun to overheat and engine temperature has risen to approximately 205OF (97OC). If generator is powering non-critical and critical loads and cannot be shutdown, use the following: a. Reduce load if possible by turning off non-critical loads. b. Check air inlets and outlets and remove any obstructions to airflow. c. Open doors or windows in generator area to increase ventilation. If engine can be stopped, follow procedure in step 3.
  • HI ENG TEMP lamp lights. Engine shuts down.
    Fix: Indicates engine has overheated (engine temperature has risen above 215°F/102°C) or coolant level is low (sets with coolant level sensor). Allow engine to cool down completely before proceeding with the following checks: a. Check coolant level and replenish if low. Look for possible coolant leakage points and repair if necessary. b. Check for obstructions to cooling airflow and correct as necessary. c. Check for a slipping fan belt and tighten if loose. d. Reset control and restart after locating and correcting problem. Contact an Onan Dealer or Distributor if none of the above.
  • Green RUN lamp lights following engine start-up.
    Fix: Indicates all engine systems are normal. No corrective action required.
  • Fuel supply is marginally low. LO FUEL
  • Engine temperature is marginally low for starting. Indicates inoperative coolant heater, (Lamp lights when engine water jacket temperature is 70°F (21 OC) or lower. Since the lamp goes out after the engine warms up there should be no cause for alarm even during initial generator set operation.) LO ENG TEMP
  • Engine has shut down because of excessive speed. OVERSPEED
  • Engine has shut down because of critically low oil pressure. LO OIL PRES
  • Engine has shut down because of critically high temperature. HI ENG TEMP
  • An undedicated fault May be factory programmed as a shutdown or non-shutdown, and as a timed or non-timed (normally set for timed shutdown). FAULT 1
  • 9. LO FUEL lamp lights. Engine continues to run.
    Fix: Indicates diesel fuel supply is running low. Check fuel supply and replenish as required.
  • 8. SWITCH OFF lamp flashes.
    Fix: Indicates Run/Stop/Remote switch is in the Stop position which will prevent automatic starting if an automatic transfer switch is used. Move the Run/Stop/Remote switch to the Remote position for automatic starting.
  • 17. Green RUN lamp does not light following engine start-up.
    Fix: Indicates possible Start/Disconnect relay failure. Contact an Onan Dealer or Distributor for assistance.

Compiled from service & troubleshooting documentation across every generator set that uses the Cummins/Onan KTA-38-GI.

Service intervals

4
ItemActionHoursMonthsNotes
Crankcase oil (new generator sets)Drain50 hrFirst service — Drain and replace the crankcase oil after the first 50 hours of operation on new generator sets
Generator bearingInspect1000 hrHave bearing inspected for wear every 1000 hours by an Onan Distributor
Generator bearing (prime power)Replace10000 hrFor prime power, replace at least every 10,000 hours or after two years
Generator bearing (standby power)Replace60 moFor standby power, replace at least every five years

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

31
TypeItemValueUnitCondition
ClearanceAir cleaner nozzle distance from element1inch25 mm minimum
PressureAir cleaner cleaning air pressure30psi207 kPa; DFW, DFY and DFZ
PressureCrankcase breather drying air pressure30psimaximum (OSHA)
PressureLow oil pressure shutdown setpoint14psi97 kPa; time delayed about 10 seconds following starter disconnect
PressureNormal engine oil pressure range50 to 70psi345 to 483 kPa
PressurePre-low oil pressure alarm (optional 12-lamp system)20psi137 kPa or less
PressureRadiator air discharge static pressure0.25inch H2O0.018 inch Hg; 450 DM, 500 DM, 600 DFY, 750 DFZ
PressureRadiator air discharge static pressure0.5inch H2O0.037 inch Hg; 450 DFW
ResistanceBattery specific gravity (recharge below)1.260specific gravityuse a hydrometer
SpeedCycle cranking option15secondsthree 15-second cranking cycles with two 15-second rest periods
SpeedFine speed adjustment range (SPEED ADJUST potentiometer)±100RPMless than
SpeedFrequency meter speed relation30r/mineach hertz equals 30 r/min
SpeedNo-load governed speed, 50 Hz 3% droop1545RPM51.5 Hz
SpeedNo-load governed speed, 50 Hz 5% droop1575RPM52.5 Hz
SpeedNo-load governed speed, 50 Hz isochronous1500RPM50.0 Hz
SpeedNo-load governed speed, 60 Hz 3% droop1854RPM61.8 Hz
SpeedNo-load governed speed, 60 Hz 5% droop1890RPM63.0 Hz
SpeedNo-load governed speed, 60 Hz isochronous1800RPM60.0 Hz
SpeedOvercrank cranking limit (standard control)75secondsstarter disengages after 75 seconds of cranking
SpeedOverspeed shutdown, 50 Hz units1850 ± 50r/min
SpeedOverspeed shutdown, 60 Hz units2100 ± 90r/min
SpeedStarter disconnect speed450 to 570r/min
TemperatureHigh engine temperature shutdown215°F102°C; time delayed about 10 seconds following starter disconnect
TemperatureLO ENG TEMP lamp setpoint70°F21°C or lower engine water jacket temperature
TemperaturePre-high engine temperature alarm205°F97°C; optional 12-lamp system
TorqueOil drain plug60-70ft.lbalso 81-95 N·m
VoltageElectrical system starting voltage24Volts DC
VoltageRandom voltage variation±1%constant loads
VoltageRating condition, ambient temperature77°F25°C; also altitude 300 feet (92 m)
VoltageVoltage adjust rheostat range±5%optional; of rated output voltage
VoltageVoltage regulation, VRAS-2 regulator±2%from no load to full load

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

FluidGradeStandardAmbientCapacityNotes
CoolantWater or water/antifreeze mixture with DCA prechargeWater clean, low in mineral content, free of chloride, sulphate, or acid; permanent type antifreezeNew engines shipped with precharge water filter; precharge water filter compatible with plain water and all permanent antifreezes except methoxy propanol base; do not use antifreeze with anti-leak additives; capacities (standard radiator): 44 gallons (166 litres) 450 DM, 500 DM, 600 DFY; 42.5 gallons (161 litres) 450 DFW; 55 gallons (208 litres) 750 DFZ
Engine oilSAE 5W syntheticAPI class CC/CD; sulphated ash not exceeding 1.85 percent; pour point 9°F (5°C) below lowest expected temperature; viscosity 10,000 mPa*s max at -31°F (-35°C) and 4.1 mm2/s min at 212°F (100°C)below -25°CFor ambient temperatures consistently below -13°F (-25°C) with no provision to keep engine warm; do not use petroleum base 5W grade oil
Engine oilSAE 10W-30API Class CC/CD, maximum sulphated ash 1.85 percent-25°C to 35°C-13°F to 95°F; capacities: 22.3 Gallons (84 litres) 450 DM, 500 DM, 600 DFY; 27 Gallons (102 litres) 450 DFW; 34 Gallons (129 litres) 750 DFZ (filters, lines and crankcase)
Engine oilSAE 15W-40API Class CC/CDabove -10°C14°F (-10°C) and above
Engine oilSAE 20W-40API Class CC/CDabove 0°C32°F (0°C) and above
FuelNo. 2 dieselEngine primarily designed for No. 2 diesel fuels; will also operate on No. 1 fuel or similar if specifications met; filter or strain fuel as tank is filled
Greasenon-conductive greaseLight coating on battery terminals to retard corrosion
Otheranti-seize compoundUse when reassembling threaded aluminum parts (coolant heater)

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

Procedures

12
Governor Gain Adjustment adjustment
  1. Close main line circuit breaker and apply approximately 1/4 of rated load.
  2. Make sure engine speed is constant.
  3. Turn GAIN potentiometer clockwise slowly until engine speed is not constant.
  4. Turn potentiometer counterclockwise until a constant speed is achieved.
  5. Turn counterclockwise an additional 1/2 division.
  6. Use SPEED ADJUST potentiometer for fine speed adjustments of less than ±100 RPM.
Governor Preliminary Adjustments adjustment
  1. Turn idle speed potentiometer counterclockwise to its stop, then clockwise 10 turns.
  2. Turn run speed potentiometer counterclockwise to its stop, then clockwise 10 turns.
  3. Turn gain potentiometer fully counterclockwise.
  4. Turn droop potentiometer fully counterclockwise for isochronous operation.
  5. Turn droop screw to approximately 40 for 3 percent droop.
  6. Turn droop screw to approximately 80 for 5 percent droop.
Air Cleaner Service (DFW, DFY) maintenance

⚠ Filters should be handled with care to prevent damage.

Tools: compressed air

  1. Loosen the eight attaching bolts and lift off the air cleaner head.
  2. Remove the air filter element from the filter housing.
  3. Blow low pressure compressed air (30 psi/207 kPa) through element from the clean side.
  4. Hold nozzle at least 1 inch (25 mm) away to avoid damaging the element.
Air Cleaner Service (DFZ) maintenance

Tools: compressed air

  1. Unsnap four latches holding head, lift off head and remove filter element.
  2. Remove and discard precleaner cartridge.
  3. Blow low pressure compressed air through pleated paper cartridge from the inside.
  4. Hold nozzle at least 1 inch (25 mm) away to avoid damaging the element.
  5. Replace pleated paper cartridge at every fourth cleaning.
Coolant Filter Service maintenance

⚠ Do not use antifreeze with an anti-leak formula; the stop leak element can prevent or retard coolant flow through the filter.

  1. Close the shutoff valve.
  2. Unscrew the coolant filter and discard.
  3. Apply a light coat of lubricating oil to the gasket surface.
  4. Install new filter and tighten by hand until seal just touches filter head.
  5. Tighten an additional one-half to three-fourths turn.
  6. Open the shutoff valve.
Coolant Heater Service maintenance

⚠ Failure to remove AC power presents a shock hazard and can cause serious personal injury or death.

⚠ Contact with hot coolant can result in severe burns.

  1. Remove AC power from coolant heater.
  2. Allow heater to cool before proceeding.
  3. Remove the head and valve assembly.
  4. Clean any scale deposits out of the tank.
  5. Remove heating element and scrape off any accumulated scale.
  6. Restore AC power to heater after system has been filled with coolant.
Cooling System Flushing maintenance

⚠ Excessive air pressure while starting the water flow could split the radiator core. Apply air pressure gradually.

Tools: flushing gun, compressed air

  1. Open upper and lower radiator hose connections and install the radiator cap.
  2. Attach flushing gun nozzle to lower radiator hose connection and fill radiator with water.
  3. Gradually apply air pressure to avoid damaging the core.
  4. Shut off air and allow radiator to refill; repeat until water runs clean.
  5. Remove thermostat to flush block; attach flushing gun to upper radiator hose.
  6. Restrict lower hose opening until block fills; apply air pressure and force water out.
  7. Replace thermostat and all hoses and refill cooling system.
Crankcase Breather Service (DFW, DFY) maintenance

Tools: compressed air

  1. Remove wing nut, flat washer and rubber washer; lift cover away from filter assembly.
  2. Lift out breather element, vapor element and gasket.
  3. Clean all parts with approved solvent; dry with compressed air (30 psi maximum OSHA).
  4. Inspect all parts, replace if necessary.
  5. Reassemble filter assembly, replace cover and secure.
Engine Oil Change maintenance

⚠ Crankcase pressure can blow out hot oil and cause serious burns. Do NOT check oil while the generator set is operating.

Tools: drain pan, torque wrench

  1. Bring engine up to operating temperature and then shut it off.
  2. Remove oil drain plug or open drain valve and collect oil in a pan.
  3. Replace drain plug or close drain valve; torque to 60-70 ft.lb (81-95 N·m).
  4. Fill crankcase to full mark on dipstick; allow for oil filters when drained.
  5. Start engine and check for oil leaks.
  6. Shut off engine, wait 15 minutes, check oil level, add oil if required.
Fuel Filter Replacement maintenance

⚠ Do not permit any flame, cigarette, or other ignition source near the fuel system.

  1. Remove both spin-off type fuel filters and discard.
  2. Fill new filters with diesel fuel and coat sealing gasket lightly with fuel.
  3. Install and tighten by hand until gasket just touches the filter head.
  4. Tighten an additional one-half to three-fourths of a turn.
Oil Filter Change maintenance

⚠ Always allow 15 minutes after engine shutdown before checking oil level.

  1. Unscrew and discard filters (DFW, DFY; DFZ see Figure 6).
  2. Fill filters with lubricating oil and lightly coat gasket sealing surface.
  3. Position filter on adapter and hand tighten until seal contacts filter head.
  4. Advance one-half to three-quarters turn; do not overtighten.
  5. Fill crankcase to H mark, run engine to verify no leaks, add oil as necessary.
Starting at Control Panel operation
  1. Move Run-Stop-Remote switch on the DC panel to the RUN position.
  2. Starter begins cranking; engine should start after a few seconds.
  3. Starter disconnects when engine reaches 450 to 570 r/min.
  4. If engine does not start, control indicates an overcrank fault after up to 75 seconds.
  5. To clear overcrank fault, place switch in STOP and momentarily depress Reset.
  6. Wait two minutes for starter motor to cool, then repeat starting procedure.

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 KTA-38-GI?

The Cummins/Onan KTA-38-GI engine has an oil capacity of 129.0 liters.

Which generators use the Cummins/Onan KTA-38-GI engine?

The Cummins/Onan KTA-38-GI powers 1 generator set(s), including Cummins/Onan 750 DFZ.

What is a common problem with the Cummins/Onan KTA-38-GI engine?

A commonly reported issue on generators using the Cummins/Onan KTA-38-GI is: Starter has been locked out because of excessive cranking time..