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Cummins/Onan KYD Engine

The Cummins/Onan KYD is a 0.3 L 1-cylinder air cooled engine rated at 3600 rpm. It powers generator sets from Cummins/Onan, including the 3.3KY, 3.6KY and 4KY. It holds 1.5 L (0.4 gal) of oil.

Also known as: Cummins KYD

0.304 L
Displacement
1
Cylinders
3600 rpm
Rated speed
1.5 L
Oil capacity
On this pageSpecsGenerator setsMaintenanceFAQTorque & specsProcedures

Engine specifications

Oil capacity1.5 L
Displacement0.304 L
Cylinders1
AspirationAir Cooled
Rated speed3600 rpm

Common problems

15
  • Starting batteries run down
    Cause: Marginal batteries, connections, or charging system or, parasitic loads
    Fix: Clean and tighten the positive (+) and negative (−) battery cable connections at the battery, vehicle frame and genset; Recharge or replace the battery. Refer to the battery manufacturer's recommendations; Have a battery charging system installed or serviced in the vehicle.
  • Processor Fault 42
  • Voltage sense fault — Controller unable to sense output voltage 27
    Fix: See an authorized Onan dealer.
  • Undervoltage fault — Controller unable to maintain rated voltage 13
    Fix: Reduce the number of connected appliances, especially when air conditioners and battery chargers are running.
  • Underfrequency fault — Engine governor unable to maintain rated frequency 15
    Fix: Reduce the number of connected appliances, especially when air conditioners and battery chargers are running.
  • Status indicator light goes out while cranking—no start
    Cause: Internal short circuit caused automatic-reset circuit protective device to trip
    Fix: Try starting again. See an authorized Onan dealer if the status indicator light flashes and then goes out again without the engine starting.
  • Status indicator light dead
    Cause: Faulty connections, no battery voltage
    Fix: Try the genset Start Switch if the remote Start Switch does not work, and vice versa; Clean and tighten the positive (+) and negative (−) battery cable connections at the battery, vehicle frame and genset; Recharge or replace the battery. Refer to the battery manufacturer's recommendations.
  • Starter engages-disengages
    Cause: Cranking voltage dips below 6 volts—low battery charge, poor connections, long cables
    Fix: Have the vehicle propulsion engine running while trying to start the genset—the battery charging alternator may be able to maintain starting voltage high enough to get the genset started; Clean and tighten the positive (+) and negative (−) battery cable connections at the battery, vehicle frame and genset; Recharge or replace the battery. Refer to the battery manufacturer's recommendations; Increase battery cable size or run parallel cables.
  • SPEED SENSE FAULT—Controller unable to sense quadrature frequency CODE NO. 45
    Fix: See an authorized Onan dealer.
  • Speed sense fault — Controller unable to sense quadrature frequency 45
    Fix: See an authorized Onan dealer.
  • Service check fault — First-level fault code—Indicates fault with second-level fault code 3
    Fix: Check the second-level fault code by pressing STOP once. The second-level fault code will have two-digits. The faults are listed in numerical order in this table.
  • PROCESSOR FAULT—Microprocessor ROM error during self-test CODE NO. 42
    Fix: See an authorized Onan dealer.
  • PROCESSOR FAULT—Microprocessor RAM error during self-test CODE NO. 43
    Fix: See an authorized Onan dealer.
  • Processor fault — Microprocessor ROM error during self-test 42
    Fix: See an authorized Onan dealer.
  • Processor fault — Microprocessor RAM error during self-test 43
    Fix: See an authorized Onan dealer.

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

Maintenance schedule

ItemSpecCapacityPart #Interval
BatteryInstallation Review and Startup (Page 20)—150 hr

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

Repair guides

21

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

Service specifications

9
TypeItemValueUnitCondition
GapMagneto Air Gap0.009-0.015inch (0.23-0.38 mm)
GapSpark Plug Gap0.020inch (0.51 mm)
GapSpark Plug Gap0.025inch (0.64 mm)
OtherIgnition Timing (magneto)25° BTDC, non-adjustable
PressureFuel line pressure at genset connection1-1/2psimust not exceed under any condition
PressureLPG Vapor Supply Pressure9-13inch (228-330 mm) Water Column (WC)
TorqueSpark Plug Tightening Torque13lbs-ft (17 N-m)
Valve clearanceExhaust Valve Lash0.002inch (0.05 mm)Cold
Valve clearanceIntake Valve Lash0.002inch (0.05 mm)Cold

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

Procedures

6
Genset Reconnections adjustment

⚠ Generator voltage is deadly

  1. Remove control panel for access to generator leads and circuit breaker terminals.
  2. Reconnect generator leads in accordance with appropriate reconnection diagram.
  3. Check voltage after reconnections.
  4. Adjust no-load voltage with adjustment pot on control panel as necessary.
Exhaust Tailpipe Installation installation

⚠ Exhaust gas is deadly

⚠ Hot exhaust tailpipe can ignite oil drain spills

⚠ Excessive back pressure can cause engine damage

Tools: U-bolt muffler clamps, tailpipe hangers

  1. Use 18-gauge 1-1/8 inch I.D. aluminized steel tubing or equivalent; do not use flexible pipe.
  2. Clamp tailpipe to muffler with U-bolt muffler clamp.
  3. Support tailpipe longer than 1-1/2 feet near end and at intervals of 3 feet or less.
  4. Use automotive-type tailpipe hangers; do not attach to combustible material.
  5. Use U-bolt clamps to connect tailpipe sections; slot overlapping pipe maximum 3/4 inch both sides.
  6. Do not route tailpipe near fuel lines or fuel tanks.
  7. Keep tailpipe at least 3 inches (76 mm) from combustible material unless insulated or shielded.
  8. Do not route tailpipe underneath oil drain or restrict air outlet.
  9. Do not route tailpipe into approach/departure angles or below axle clearance line.
  10. Do not interconnect genset and vehicle engine exhaust systems.
  11. Extend tailpipe at least 1 inch (25 mm) beyond vehicle perimeter and 6 inches (153 mm) from openings.
  12. Ensure tailpipe deflector does not cause excessive back pressure.
Location, Mounting and Enclosure installation

⚠ Genset can fall from vehicle if supporting structure is weak

⚠ Fire is deadly; install fire-resistive barrier

⚠ Exhaust gas and fire are deadly

  1. Verify support structure resists dynamic weight: ±561 lbs vertical (±3 g) and ±187 lbs horizontal (±1 g).
  2. Secure genset with six 5/16-18 NC bolts; protrude at least 1-1/2 threads beyond weld nuts, maximum 1/2 inch.
  3. For below-floor mounting, use Onan mounting kit and Underfloor Template 539-1535; reinforce wood floor with steel.
  4. For above-floor mounting, construct vapor-tight, fire-resistive compartment of 26 gauge galvanized steel or equivalent.
  5. Shield cooling air openings from rain, road splash and debris.
  6. Provide access for fuel and battery connections and periodic maintenance; use Compartment Template 539-1546 for oil drain cutout.
  7. Do not share compartment or ventilation with batteries or fuel tanks.
  8. Provide at least 40 in2 (258 cm2) free-air inlet; keep cooling air unobstructed.
  9. Maintain required clearances: 1 inch left, 1/4 inch sides, 1 inch top, 1-1/2 inch front if inlet not aligned.
  10. Use self-extinguishing acoustic insulation rated at least 200°F (90°C); do not line compartment bottom.
Remote Control Connections installation

⚠ Exhaust gas is deadly; seal all wiring openings

  1. Push remote control wire harness connector through entrance hole and snap to genset connector.
  2. For harness made by others, use insulated 18 AWG copper conductors up to 30 feet (9 metres).
  3. Use heavier gauge conductors for greater distances and flexible sheathing to protect wiring.
  4. Route control leads separately from AC power leads.
  5. Seal opening where leads enter vehicle interior with silicone rubber or equivalent.
Separate Gasoline Fuel Pickup Tube Installation installation

⚠ Excessive fuel pressure can flood genset causing fire

⚠ Sparks can ignite gasoline

Tools: stainless steel hose clamps

  1. Contact vehicle chassis manufacturer regarding second fuel pickup installation.
  2. Do not change fuel fill tube, fill limiter vent, vapor canister, vapor lines, filler cap or fuel system without approval.
  3. Terminate genset pickup above vehicle pickup to prevent running vehicle out of fuel.
  4. Use 1/4 inch I.D. fuel hose (SAE 30-R7) and stainless steel hose clamps for connection.
  5. Run fuel line at or above top of fuel tank; maximum fuel pump lift 36 inches (914 mm).
  6. Route fuel lines away from electrical wiring and hot exhaust components.
Startup operation

⚠ Batteries give off explosive gases

⚠ Exhaust gas is deadly

  1. Complete Installation Review checklist.
  2. Connect battery cables to battery, positive (+) cable first.
  3. Read Operator’s Manual and perform maintenance and pre-start checks.
  4. Check engine oil level before starting.
  5. Start and operate genset following Operator’s Manual instructions and safety precautions.
  6. Check for fuel and exhaust leaks and unusual noises under full and intermediate loads.
  7. Do not place genset in service until all fuel and exhaust leaks are fixed and operation is satisfactory.

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 KYD?

The Cummins/Onan KYD engine has an oil capacity of 1.5 liters.

What is the displacement of the Cummins/Onan KYD?

The Cummins/Onan KYD has a displacement of 0.304 liters with 1 cylinders.

Which generators use the Cummins/Onan KYD engine?

The Cummins/Onan KYD powers 3 generator set(s), including Cummins/Onan 3.3KY, Cummins/Onan 3.6KY, Cummins/Onan 4KY.

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

A commonly reported issue on generators using the Cummins/Onan KYD is: Starting batteries run down. Cause: Marginal batteries, connections, or charging system or, parasitic loads. Fix: Clean and tighten the positive (+) and negative (−) battery cable connections at the battery, vehicle frame and genset; Recharge or replace the battery. Refer to the battery manufacturer's recommendations; Have a battery charging system installed or serviced in the vehicle..