The Cummins/Onan MCCK is a 0.82 L 2-cylinder unspecified engine rated at 1800 rpm. It powers generator sets from Cummins/Onan, including the 4.0 MCCK, 4MCCK, 6.5 MCCK and 605MCCK. It holds 3.3 L (0.9 gal) of oil and 3.3 L (0.9 gal) of coolant.
Also known as: Onan MCCK
| Oil capacity | 3.3 L |
|---|---|
| Coolant capacity | 3.3 L |
| Displacement | 0.816 L |
| Cylinders | 2 |
| Aspiration | Unspecified |
| Rated speed | 1800 rpm |
How to read your Cummins/Onan engine serial & model number →
| Symptom | Cause | Remedy |
|---|---|---|
| No AC voltage | Blown fuse or circuit breaker (if used) | Look for cause and repair. Then replace fuse or reset breaker. |
| No AC voltage | Disconnected wire or lead with collector rings; brushes not making contact | Reconnect wire or wires. |
| No AC voltage | Brushes not making contact with collector rings | Check brush springs for free movement or brushes which may be excessively worn. |
| No AC voltage | Open, grounded or short circuit in field or armature winding | Test with ohmmeter or continuity tester and repair or replace as necessary. |
| Low AC output | External short circuit on line | Locate and eliminate short circuit problem. |
| Low AC output | Generator overloaded | Remove part of load. |
| Low AC output | Shorted or grounded circuit in field or armature winding | Test with continuity tester or ohmmeter and replace if defective. |
| Low AC output | Engine not running properly causing generator to slow | Refer to Engine Section-Troubleshooting. |
| Noisy generator | Defective bearing in end bell | Replace bearing. |
| Noisy generator | Brush rig loose | Retorque. |
| Noisy generator | Armature and field frame rubbing together | Check generator alignment and clean air gap between arm and field of varnish lumps. |
| Generator overheats | Generator overloaded | Remove part of load. |
| Generator overheats | Windings and parts covered with oil or dirt | Clean generator. |
| Generator overheats | Air intake restricted or incoming air too hot | Take necessary steps to allow for proper cooling. |
| Generator overheats | Shorted, open or grounded circuit in armature or field windings | Test with ohmmeter or continuity tester and replace if defective. |
| Engine does not crank | Battery cables not tight | Check battery. Are battery cables tight? |
| Engine does not crank | No battery voltage between control TB1 terminal 3 and B+ terminal when start switch S1 is pushed to START | Replace start-stop switch S1. |
| Engine does not crank | No battery voltage between start solenoid terminal S1 and ground when start switch S1 is pushed to START | Replace start solenoid K1 which is defective. |
| Engine does not crank | Generator fault | Perform generator tests. See Generator section. |
| Engine cranks but does not start | No battery voltage between stop relay K2 terminal 5 and a good ground when start switch is pushed to START | Check wiring to stop relay K2 and connections. Replace stop relay if necessary. |
| Engine cranks but does not start | Fuel solenoid does not operate when start switch is pressed to START | Check wires to fuel solenoid, check solenoid, and replace if necessary. |
| Engine cranks but does not start | No fuel pulsating from fuel line when control positive terminal of ignition coil is jumpered to battery positive post | Check wire lead to fuel pump, check fuel pump, and replace if necessary. |
| Engine cranks but does not start | Ignition system fault | See the Ignition System section in the ENGINE portion of the Master Service Manual (922-0501). |
| Engine starts but stops when start switch is released | No voltage indicated at start solenoid relay K1 terminal S1 after start switch was released | Check wire connections from generator to start solenoid K1 terminal S1. If OK, perform generator test (Generator Troubleshooting and Procedures). |
| Engine starts but stops when start switch is released | Resistor R1 and resistor connections not OK | Replace resistor or wire leads as necessary. |
| Engine starts but stops when start switch is released | Reverse current diode CR1 shorted or open, or diode connections faulty | Replace if necessary. |
| Generator set is running - then stops | Engine started but stopped when switch S1 was released | See Engine starts but stops when start switch is released. |
| Generator set is running - then stops | No battery voltage between stop relay K2 terminal 5 and a good ground when start switch is pushed to START | Replace stop relay K2. |
| Generator set is running - then stops | Engine does not start and run when stop relay terminals 5 and 11 are jumpered | Check resistor R1 and resistor connections. Are they OK? |
| Generator set is running - then stops | Resistor R1 and resistor connections not OK | Repair wire leads or replace resistor as necessary. |
| Generator set is running - then stops | Stop relay K2 does not operate when battery positive is jumpered to stop relay K2 terminal 9 | Perform generator tests (See Generator Troubleshooting and Procedures). |
| Low battery - no high charge rate | Ammeter does not indicate higher charge rate when two-step voltage regulator relay terminals BAT and B are jumpered | Replace two-step voltage regulator relay K3. |
| Low battery - no high charge rate | Resistor R2 or resistor connections faulty | Check resistor R2, resistor connections, and replace if necessary. |
| Engine does not crank | No battery voltage between control terminal 3 and B+ terminal when start switch is pushed to START | Replace start-stop switch S1. |
| Engine does not crank | No battery voltage between terminal 7 of the start disconnect relay assembly and battery B+ terminal when start switch S1 is pushed to START | Replace start disconnect relay from start disconnect assembly. |
| Engine does not crank | No battery voltage at start solenoid relay terminal S1 when start switch is pushed to START | Replace start solenoid relay K1. |
| Engine cranks but does not start | No battery voltage between control B+ terminal and terminal 9 of the start disconnect relay assembly when start switch S1 is pushed to START | Replace the start disconnect printed circuit board. |
| Engine cranks but does not start | No battery voltage between control terminal 2 and 1 when start switch is pushed to START | Check resistor R3 and resistor connections. Are they OK? |
| Engine cranks but does not start | Resistor R3 or resistor connections faulty | Repair wire lead connections or replace resistor as required. |
| Engine cranks but does not start | Start disconnect relay K4 defective | Replace start disconnect relay K4. |
| Engine cranks but does not start | Red button on low oil pressure relay K5 out | Wait at least one minute, then push in red button. |
| Engine cranks but does not start | Low oil level or low oil pressure switch S4 fault | Check oil level. If okay, remove wire lead from low oil pressure switch S4 and push start switch. Does engine crank and run? |
| Engine cranks but does not start | Grounded wire lead to low oil pressure switch S4; low oil pressure switch S4 or resistor R4 faulty | Check for a grounded wire lead to the low oil pressure switch S4. Check low oil pressure switch S4 and resistor R4. Replace as necessary. |
| Engine cranks but does not start | No battery voltage at stop relay K2 terminal 5 when start switch S1 is pushed to START | Check wiring to stop relay K2 and connections. Replace stop relay if necessary. |
| Engine cranks but does not start | Engine does not crank and run when resistor RT1 terminal is jumpered with wire lead to low oil pressure relay K5 | Check low oil pressure relay K5 and replace if necessary. |
| Engine cranks but does not start | Engine does not crank and run when high water temperature switch S3 is jumpered | Check high water temperature switch S3 and wiring. Replace as necessary. |
| Engine cranks but does not start | Fuel solenoid K6 does not operate when start switch S1 is pushed to START | Check wire to fuel solenoid, check fuel pump, and replace if necessary. |
| Engine cranks but does not start | No battery voltage at the + terminal of the ignition coil when start switch S1 is pushed to START | Check wiring to stop relay K2 and connections. Replace stop relay if necessary. |
| Engine cranks but does not start | Low oil level or low oil pressure switch fault | Check oil level. If okay, remove wire lead from low oil pressure switch and push start switch. Does engine crank and run? |
| Engine cranks but does not start | Wire lead from low pressure switch grounded | Repair or replace wire lead. |
| Engine cranks but does not start | Low oil pressure switch faulty | Check low oil pressure switch and replace if necessary. |
| Engine cranks but does not start | High air temperature switch fault | Remove wire lead from high air temperature switch and push start switch S1. (Do not let wire lead ground while disconnected). Does engine crank and run? |
| Engine cranks but does not start | Wire lead from high air temperature switch grounded | Repair or replace wire lead. |
| Engine cranks but does not start | High air temperature switch faulty | Check high air temperature switch and replace if necessary. |
| Engine cranks but does not start | No fuel pulsating from fuel line when B+ is momentarily jumpered to fuel pump | Check wire lead to fuel pump, check fuel pump and replace if necessary. |
| Engine starts - but stops when start switch is released | Resistor R2 and resistor connections in control not OK | Replace resistor or wire leads as necessary. |
| Engine starts - but stops when start switch is released | Generator fault | Check wire connections from generator to start solenoid K1 terminal S1. If OK, perform generator tests (see Generator Troubleshooting and Procedures). |
| Engine is running - then stops | High air temperature, high water temperature, or low oil pressure condition (if applicable) which would shut down the engine | Check the unit for a high air temperature, high water temperature, or low oil pressure condition (if applicable) which would shut down the engine. |
| Engine is running - then stops | Engine did not start when cranked with DC voltmeter connected to IGN terminal of control terminal block TB1 | If no safety shutdown occurred, connect a DC voltmeter to the IGN terminal of control terminal block TB1 (control cover open). Crank the engine. Does engine start? |
| Engine is running - then stops | Engine did not keep running after start switch was released | Recheck for high air temperature, low oil condition, etc., which may have occurred. |
| Low battery - no high charge rate | Resistor R1 or resistor connection faulty | Check resistor R1 and resistor connection and replace if necessary. |
| Engine does not crank | Problem lies in the three-wire adapter board or the remote switch (generator set starts using the generator set control) | Check relay K2 of the adapter by jumping terminal 3 to ground. If the relay does not operate or its contacts do not close to energize the start circuit, replace the board. |
| Engine does not crank | Start disconnect adapter P.C. board below the generator set control assembly P.C. board | Jumper between control terminal 16 and start solenoid terminal K1-S. Press start switch A1S1. Does engine crank? |
| Engine does not crank | Start disconnect adapter P.C. board faulty | Replace start disconnect adapter P.C. board. |
| Engine does not crank | No battery voltage between control terminal 6 and ground when Hand Crank ELECTRIC switch A1S1 is pushed | Remove control cover and jumper terminal 5 to terminal 6. Is battery voltage present between terminal 6 and ground? |
| Engine does not crank | Switch A1S1 faulty | Replace switch A1S1. |
| Engine does not crank | Battery cables incorrect polarity or fuse F1 blown | Check battery cables for correct polarity. Replace fuse F1 with a 9-ampere, in-line fuse. Push start switch A1S2. |
| Engine does not crank | Less than 8 volts present from terminal 9 to ground with start switch A1S2 depressed | With start switch A1S2 depressed, is at least 8 volts present from terminal 9 to ground? |
| Engine does not crank | Start solenoid K1 does not operate when solenoid coil terminal S is jumpered to battery | Jumper solenoid coil terminal S to battery. Does start solenoid K1 operate? |
| Engine does not crank | Start solenoid is defective | Replace start solenoid |
| Engine does not crank | Faulty start switch A1 S2 | Replace start switch A1 S2 |
| Engine does not crank | Defective transistor A1Q2 | Replace control P.C. board |
| Engine cranks but does not start | Faulty switch A1 S1 or diode A1 CR1 | Replace control P.C. board |
| Engine cranks but does not start | No battery voltage at control terminal 6 when start switch A1 S2 is depressed | Check transistor A1Q2; if defective, replace control P.C. board |
| Battery loses excess water | Battery terminal voltage exceeds 14 volts at 100°F (38°C) or above, 15 volts at 50 to 100°F (10 to 38°C), or 16 volts at 50°F (10°C) or below | Replace control P.C. board |
| Engine won't start and electric fuel pump won't work unless hand crank switch A1S1 is pushed during cranking. Engine runs okay after starting with hand crank switch. | Diode A1CR1 is destroyed through accidental grounding of terminal 6 or the leads supplying current to the ignition coil, electric fuel pump or fuel solenoid when start switch closes | To prevent future failure of diode A1 CR1 on units without 9-ampere fuse on terminal 5, add in-line fuse package #321-0212. Refer to Product Support Bulletin #57 |
| Engine stops running as soon as start switch is released | Diode A1 CR2 is destroyed through accidental grounding of terminal 6 or the leads supplying current to the ignition coil, electric fuel pump or fuel solenoid, while engine is running | To prevent future failure of diode A1 CR2 on units without 9-ampere fuse on terminal 5, add in-line fuse package #321-0212. Refer to Product Support Bulletin #57. The fuse does not protect A1 CR2, but will blow during cranking if terminal 6 is grounded |
| Start solenoid will not energize (check for faulty solenoid before checking following) | Diode A1CR4 may be burned out if battery connections are accidentally reversed on units not protected by 9-ampere fuse F1 on terminal 5 | To prevent future failure of diode A1 CR4 on units without 9-ampere fuse on terminal 5, add in-line fuse package #321-0212. Refer to Product Support Bulletin #57 |
| Start solenoid will not energize (check for faulty solenoid before checking following) | Accidental reverse battery connection to units not protected by in-line fuse package #321-0212 may damage diode A1CR5 | To prevent future failure of diode A1CR5 on units without 9-ampere fuse on terminal 5, add in-line fuse package #321-0212. Refer to Product Support Bulletin #57 |
| Start solenoid won't energize (controls without start disconnect adapter) | On units without 9-ampere fuse on terminal 5, accidental grounding of terminal 9 or reverse battery connections may damage transistor A1 Q2 | To prevent future failure of transistor A1Q2, on units without 9-ampere in-line fuse on terminal 5, install in-line fuse package #321-0212. Refer to Product Support Bulletin #57 |
Fault codes and symptom→remedy steps extracted from this engine’s service/owner documentation; verify against the official manual before servicing. Showing the first 80 of 154 entries.
Compiled from service & troubleshooting documentation across every generator set that uses the Cummins/Onan MCCK.
| Item | Spec | Capacity | Part # | Interval | |
|---|---|---|---|---|---|
| Air filter | — | ||||
| Fuel filter | — | 250 hr | |||
| Oil filter | — | ||||
| Battery | — | ||||
| Belt | — | ||||
| Coolant | 3.3 litres | — | |||
| Coolant filter | — | ||||
| Oil | 3.5 | — | |||
| Spark plug | 0.025 inches, 20° BTC timing | 927-0224 | 250 hr | Amazon eBay |
Pooled from every document that names this exact engine — confirm the interval and part number against your unit's serial number.
Step-by-step procedures compiled from the Cummins/Onan service manual for this engine.
| Item | Action | Hours | Months | Notes |
|---|---|---|---|---|
| Crankcase oil | Change | 50 hr | Under dirty conditions; change more often in dusty conditions | |
| Cylinder head bolts | Adjust | 50 hr | First service — Retorque to original specified torque after engine has reached normal temperature and cooled, before it has run fifty operating hours | |
| Governor linkage | Lubricate | 50 hr | Clean joints and lubricate with graphite | |
| Spark plugs | Replace | 250 hr | Inspect, clean and regap each time removed | |
| Electric fuel pump filter | Check | 500 hr | Drain fuel pump and check filter element every 500 hours | |
| Breaker arm pivot shaft | Lubricate | 1200 hr | Place a drop of light oil on breaker arm pivot shaft every 1200 operating hours | |
| Cooling system | Clean | 12 mo | Clean and flush at least once a year / annually; replace antifreeze annually | |
| Cooling system | Drain | 12 mo | Flush the system at least once a year, and more often if operation indicates clogged passages, pump wear, or overheating | |
| Pressure cap | Replace | 24 mo | Replace every two years or when malfunctioning | |
| Stored fuel | Replace | 3 mo | Change stored fuel as often as every three months, especially where there is a great variation in temperatures |
Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.
| Type | Item | Value | Unit | Condition |
|---|---|---|---|---|
| Clearance | Accessory clearance around unit for inspection/air circulation | one inch minimum | in (25.4 mm) | |
| Clearance | Camshaft end play | 0.012 | in | |
| Clearance | Connecting rod end play | 0.0030 | in | |
| Clearance | Crankshaft end play | 0.0038 | in | |
| Clearance | Crankshaft main bearing journal - standard size | 2.000 | in | |
| Clearance | Crankshaft rod bearing journal - standard size | 1.6260 | in | |
| Clearance | Cylinder bore - standard size | 3.250 | in | |
| Clearance | Oil pump gear backlash | 0.016 | in | |
| Clearance | Piston pin in piston | 0.005 | in | at 70 deg F |
| Clearance | Piston pin in rod | 0.0035 | in | at 70 deg F |
| Clearance | Piston to cylinder, Conformatic type | 0.003 | in | measured below oil controlling ring, 90 deg from pin |
| Clearance | Timing gear backlash | 0.0023 | in | |
| Clearance | Valve clearance - exhaust | Min .011 / Max .013 | in (0.28-0.33 mm) | |
| Clearance | Valve clearance - intake | Min .011 / Max .013 | in (0.28-0.33 mm) | |
| Clearance | Valve face angle | 44 | degrees | |
| Clearance | Valve seat angle | 45 | degrees | |
| Clearance | Valve seat face width | 1/32 to 3/64 | in | |
| Clearance | Valve seat interference width | 3/64 | in | |
| Clearance | Valve stem in guide - exhaust | 0.004 | in | |
| Clearance | Valve stem in guide - intake | 0.0025 | in | |
| Gap | Breaker point gap (full separation) | 0.020 | in | full separation |
| Gap | Carburetor float level | 1/8 | in (3.18 mm) | |
| Gap | Piston ring gap in cylinder | 0.023 | in | |
| Gap | Spark plug gap | 0.025 | in (0.64 mm) | |
| Gap | Spark plug gap - gasoline fuel | 0.025 | in | |
| Other | Camshaft center pin extension | 3/4 | in | from camshaft end |
| Other | Carburetor throttle lever clearance to stop pin | 1/32 | in | engine stopped, no load, governor arm held in closed throttle position |
| Other | Cooling system water flow | below 3.5 | GPM | indicates pump/passage problem |
| Other | Gear cover oil seal depth | 31/32 | in | from mounting face of cover |
| Other | Gear cover thin open-face seal depth | 1-7/64 | in | from mounting face of cover |
| Other | Governor cup in-and-out travel | 7/32 | in | |
| Other | Governor roll (stop) pin protrusion | 3/4 | in | from cover mounting surface |
| Other | Ignition timing | 20 deg BTC | degrees before top center | |
| Other | Water pump belt deflection | 1/2 | in (13 mm) at 15 lb (67 N) | |
| Pressure | Compression (PSI sea level) | 130-140 | PSI (897-966 kPa) | cold |
| Pressure | Exhaust back pressure at full load (max) | 3 | inches of Mercury (10 kPa) | full load |
| Pressure | Fuel pump pressure | 2 and 3 | psi | gauge held 16 in above the fuel pump, engine at governed speed |
| Pressure | Oil pressure | 25 to 40 | pounds | at operating temperature |
| Resistance | Choke heater resistance | 30.6 to 37.4 | ohms | 12-volt system, element at room temperature |
| Resistance | Choke solenoid coil resistance | 2.09 to 2.31 | ohms | 12-volt system |
| Resistance | Ignition coil primary winding resistance | 5 to 2 | ohms | |
| Resistance | Ignition coil secondary winding resistance | 4,000 to 10,000 | ohms | |
| Speed | Carburetor float setting | 0.02 +/- 0.02 | in (0.51 +/- 0.51 mm) | inverted, without gasket |
| Speed | Ignition timing advance | 25 | degrees before top center | |
| Speed | Maximum no-load speed | 1890 | RPM (63 Hz) | no load |
| Speed | Minimum full-load speed | 1770 | RPM (59 Hz) | full load |
| Speed | Throttle stop screw setting | 56 | hertz | no load, throttle closed |
| Temperature | High exhaust temperature cut-off switch | 230 | F (111 C) | |
| Temperature | High water temperature cut-off switch closes | 160 | deg F | approximately |
| Temperature | High water temperature cut-off switch opens | 200 | deg F | approximately |
| Temperature | Thermostat fully open | 165 | deg F | |
| Temperature | Thermostat opening - heat exchanger/keel cooled | 180 | F (82 C) | |
| Temperature | Thermostat opening - sea water cooled | 145 | F (63 C) | |
| Temperature | Thermostat starts to open | 145 | deg F | |
| Torque | Connecting rod bolts | 27-29 | ft. lbs. | |
| Torque | Cylinder head bolts | 29-31 | ft. lbs. | |
| Torque | Cylinder head torque | 29-31 | lb.ft (39-42 N·m) | |
| Torque | Exhaust manifold screws | 15-20 | ft. lbs. | |
| Torque | Flywheel mounting screws | 35-40 | ft. lbs. | |
| Torque | Fuel pump mounting screws (approximately) | 10-15 | ft. lbs. |
Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.
| Fluid | Grade | Standard | Ambient | Capacity | Notes |
|---|---|---|---|---|---|
| Coolant | Clean ethylene glycol antifreeze (minimum 50-50 mix with water) | 3.5 quarts (3.3 litres) | Fill closed cooling system with clean, alkali-free water and rust inhibitor or antifreeze; complete change every year; test antifreeze periodically | ||
| Coolant | Raw liquid coolant (fresh water or sea water); closed-type system uses fresh water with anti-freeze | Use anti-freeze if there is danger of freezing; use a rust inhibitor in the closed water system; flush at least once a year | |||
| Engine oil | API SE or SE/CC detergent oil | 3.5 quarts (3.3 litres) | Do not use service DS oil; do not mix brands or grades; use proper SAE viscosity per Oil Recommendation Chart Figure 24 | ||
| Fuel | Regular grade gasoline | Premium fuels contain more lead causing more combustion chamber deposits; stored fuel should be changed as often as every three months | |||
| Fuel | Unleaded or Regular Gasoline | Do not use highly leaded premium fuels; below 0F adjust main jet for slightly richer fuel mixture | |||
| Grease | Fibrous grease or stiff cup grease | Fill the space between the oil seal lips to improve sealing | |||
| Other | Permatex or thread-sealing compound | Use on all threaded connections when making cooling system repairs |
Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.
⚠ If a voltmeter is not available, use the same procedure but mark the point where arcing begins.
Tools: voltmeter
⚠ Be careful not to lose the buoyancy spring or tension spring on the viton tip float needle and seat assembly.
Tools: Phillips screwdriver
⚠ Don't force the needle valves against their seats; this will bend the needle.
Tools: voltmeter and/or frequency meter, tachometer
⚠ The 4-volt coils can be tested on a 6-volt tester; a 12-volt tester will destroy the coil in a few seconds.
Tools: timing light or continuity test lamp
Tools: drill or drill bit shank
Tools: feeler gauge, standard automotive type wrench
Tools: tank of known capacity
Tools: pressure gauge or manometer
Tools: thermometer, water bath
Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.
| Voltage | Phase | Connection | Leads | Notes |
|---|---|---|---|---|
| 120 | 1PH, 2W | M1, M2, M3, M4 output leads; grounded load wire | M1, M2, M3, M4 | Only half nameplate rating can be taken off each 120 volt connection |
| 120/240 | 1PH, 3W | 120/240 load wire connections (3-wire) | M1, M2, M3, M4 | Observe negative electric generating set ground; revolving armature generator leads marked M1, M2, etc. |
| 120/240 | 1PH, 3W | Shore power wiring connections | Grounded neutral conductor (white), ungrounded conductor (black), equipment grounding conductor (green) | Use Onan double-throw transfer switch 308-0269 (2-pole, 63 amp) or 308-0270 (3-pole, 63 amp) |
Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.
The Cummins/Onan MCCK engine has an oil capacity of 3.3 liters.
The Cummins/Onan MCCK has a displacement of 0.816 liters with 2 cylinders.
The Cummins/Onan MCCK powers 4 generator set(s), including Cummins/Onan 4.0 MCCK, Cummins/Onan 4MCCK, Cummins/Onan 6.5 MCCK, Cummins/Onan 605MCCK.
A commonly reported issue on generators using the Cummins/Onan MCCK is: Sharp metallic thud. Especially when cold engine first started. Cause: Low oil supply. Fix: Add oil.