Cummins/Onan MDJC troubleshooting: 2 fault codes and 120 symptom-cause-remedy entries from the manufacturer's own service documentation.
Cummins/Onan MDJC — full specs, parts & maintenance.
All Cummins/Onan fault codes →
| Code | Meaning |
|---|---|
| e008 | No specific name provided for e008 |
| 10 | Overload |
| Symptom | Cause | Remedy |
|---|---|---|
| Engine will not crank | Battery discharged | Recharge |
| Engine will not crank | Loose connections | Tighten connections |
| Engine will not crank | Defective starting circuit | Repair or replace as necessary |
| Engine will not crank | Defective starting motor on revolving field generator | Repair or replace as necessary |
| Engine will not crank | Defective switch | Replace |
| Engine will not crank | Poor generator brush contact on revolving armature generator | Replace brush. Refinish surface |
| Engine cranks too stiffly | Too heavy oil in crankcase | Drain, refill with lighter oil |
| Engine cranks too stiffly | Engine stuck | Disassemble and repair |
| Engine cranks too stiffly | Load connected | Disconnect |
| Engine cranks too stiffly | Decompression release (on 1 cyl diesel) at running position | Place at start position |
| Engine will not start when cranked | Air in fuel system | Bleed the fuel system |
| Engine will not start when cranked | Lack of fuel or faulty injection caused by dirty fuel | Refill the tank. Check the fuel system. Clean, adjust, or replace parts necessary |
| Engine will not start when cranked | Clogged fuel filter | Clean strainer (primary). Install new cartridge (secondary) |
| Engine will not start when cranked | Poor compression | Tighten cylinder head. Replace head gasket. If still not corrected, grind the valves. Replace piston rings, if necessary |
| Engine will not start when cranked | Wrong timing | Check injection pump timing |
| Engine stops when start switch is released | Centrifugal switch remained open | Clean and adjust |
| Engine runs but voltage does not build up | Poor brush contact | See that brushes seat well, are free in their holders, are not worn too short, and have good spring tension |
| Engine runs but voltage does not build up | Open circuit, short circuit, or ground in generator | Replace parts necessary |
| Engine runs but voltage does not build up | Residual magnetism lost | Spec B exciters - press residual reset button; spec A exciters — consult dealer |
| Engine runs but voltage does not build up | Dirty relay contacts in 02SX Magneciter | Clean with paper |
| Engine runs but voltage does not build up | Faulty Magneciter | Trouble shoot Magneciter |
| Excessive oil consumption, light blue smoky exhaust | Poor compression, usually due to worn piston, rings, or cylinder | Refinish cylinder. Install oversize piston and rings |
| Excessive oil consumption, light blue smoky exhaust | Oil leaks from oil base or connections. This does not cause smoky exhaust | Replace gaskets. Tighten screws and connection. Check breather valve |
| Excessive oil consumption, light blue smoky exhaust | Oil too light or diluted | Drain, refill with correct oil |
| Excessive oil consumption, light blue smoky exhaust | Worn engine | Repair as necessary |
| Excessive oil consumption, light blue smoky exhaust | Worn intake valve guide or valve stem | Replace |
| Excessive oil consumption, light blue smoky exhaust | Engine misfiring | Refer to symptoms of engine misfiring |
| Excessive oil consumption, light blue smoky exhaust | Too much oil | Drain excess oil |
| Black, smoky exhaust, excessive fuel consumption, possible low power under heavy load | Generator overloaded. Black smoky exhaust normal condition with overload | Reduce load to within rated capacity. If smoky condition continues, stop unit and investigate |
| Black, smoky exhaust, excessive fuel consumption, possible low power under heavy load | Poor compression | Tighten cylinder head, grind or replace valves, replace piston rings as needed |
| Black, smoky exhaust, excessive fuel consumption, possible low power under heavy load | Poor grade or dirty fuel | Use only clean, recommended fuel |
| Black, smoky exhaust, excessive fuel consumption, possible low power under heavy load | Injection pump or nozzle not operating properly | Clean nozzle. If necessary, install new nozzle or injection pump |
| Black, smoky exhaust, excessive fuel consumption, possible low power under heavy load | Faulty injection timing | Check injection pump timing |
| Black, smoky exhaust, excessive fuel consumption, possible low power under heavy load | Dirty air cleaner | Clean |
| Engine stops unexpectedly | Fuel tank empty | Refill |
| Engine stops unexpectedly | Safety switch operated (where used) | Correct the overheating or the lubrication failure. Press reset switch. Replace unless one of the next two remedies permanently corrects the trouble |
| Dull metallic thud. If not bad, may disappear after few minutes operation. If bad, increases with load | Loose crankshaft bearing | Replace |
| Dull metallic thud. If not bad, may disappear after few minutes operation. If bad, increases with load | Low oil supply | Add oil |
| Dull metallic thud. If not bad, may disappear after few minutes operation. If bad, increases with load | Oil badly diluted | Change oil |
| Sharp metallic thud, especially when cold engine first started | Valve clearance too great | Adjust. Replace faulty valve system |
| Sharp metallic thud, especially when cold engine first started | Broken valve spring | Install new spring |
| Tapping sound | Loose piston | If noise only slight and disappears when engine warms up, no immediate attention needed. Otherwise replace worn parts |
| Hollow clicking sound with cool engine under load | Loose connecting rod bearing | Adjust or replace |
| Light pounding knock (knock from firing of fuel is normal) | Low oil supply | Add oil |
| Light pounding knock (knock from firing of fuel is normal) | Oil badly diluted | Change oil |
| Engine races | Too much fuel injected. STOP UNIT AT ONCE! | Check governor performance and linkage condition |
| Engine misfires | Faulty injection | Clean fuel system. Use clean recommended fuel |
| Engine misfires | Low compression | Tighten cylinder head. Service valves and piston rings as needed |
| Low oil pressure | Defective gauge | Replace |
| Low oil pressure | Oil too light or diluted from leaking fuel pump diaphragm | Drain. Refill with proper oil. Repair or replace transfer pump |
| Low oil pressure | Oil too low | Add oil |
| Low oil pressure | Oil relief valve not seating | Clean. Replace if needed |
| Low oil pressure | Badly worn bearings | Replace |
| Low oil pressure | Sludge on oil cup screen | Clean screen and oil sump |
| Low oil pressure | Badly worn oil pump | Replace |
| High oil pressure | Defective gauge | Replace |
| High oil pressure | Oil too heavy grade | Drain. Refill |
| High oil pressure | Clogged oil passages | Clean all lines and passages |
| High oil pressure | Oil relief valve stuck | Clean by-pass. Replace if needed |
| Engine overheating | Poor coolant circulation | Maintain supply |
| Engine overheating | Improper lubrication | See Low Oil Pressure |
| Engine overheating | Wrong injection timing | Retime |
| Engine overheating | Generator overloaded | Reduce load |
| Voltage low at far end of line but normal near power plant | Too small line wire for load and distance | Install larger or extra wires or reduce load |
| Electric motor runs too slowly and overheats at far end of line but OK if used near power unit | Too small line wire for load and distance | Install larger or extra wires or reduce load |
| Voltage unsteady but engine not misfiring | Speed too low | Adjust governor to correct speed |
| Voltage unsteady but engine not misfiring | Poor brush contact (or poor commutation on revolving armature models) | See that brushes seat well on commutator, are free in their holders, are not worn too short, and have good spring tension |
| Voltage unsteady but engine not misfiring | Loose connections | Tighten connections |
| Voltage unsteady but engine not misfiring | Fluctuating load | Correct any abnormal load condition causing trouble |
| Noisy and excessive arcing of brushes (revolving armature model) | Rough commutator | Turn down. Undercut mica between bars |
| Noisy and excessive arcing of brushes (revolving armature model) | Dirty commutator | Clean |
| Noisy and excessive arcing of brushes (revolving armature model) | Brushes not seating properly | Sand to a good seat |
| Noisy and excessive arcing of brushes (revolving armature model) | Open circuit in armature | Replace |
| Noisy and excessive arcing of brushes (revolving armature model) | Brush rig out of position | Line up properly |
| Generator overheating (approximately 160°F. higher than ambient) | Brush rig out of position (Revolving armature generator) | Adjust |
| Generator overheating (approximately 160°F. higher than ambient) | Overloaded | Reduce load |
| Voltage drops under heavy load | Engine lacks power | See remedies for engine misfires |
| Voltage drops under heavy load | Poor compression | Tighten cylinder head and spark plug. If still not corrected, grind the valves. Replace piston rings, if necessary |
| Voltage drops under heavy load | Faulty injection | Check the fuel system. Clean, adjust or replace parts necessary |
| Voltage drops under heavy load | Dirty air cleaner | Clean |
| Voltage drops under heavy load | Restricted exhaust line | Clean or increase the size |
| No build up of AC output voltage — Is Field Breaker CB21 on control panel ON? | Proceed to step 2 if YES; proceed to step 3 if NO | |
| No build up of AC output voltage — Connect jumper wire across terminals of Field Breaker, CB21. Does AC output voltage build up? | Field breaker defective | If voltage builds up REPLACE FIELD BREAKER; if not, proceed to step 4 |
| No build up of AC output voltage — Push to reset Field Breaker. Does AC output voltage build up? | If voltage builds up but is high, low, unstable, or causes tripping of Field Breaker, refer to Tables B, C, or D | |
| No build up of AC output voltage — Disconnect alternator stator leads 1 & 2 from TB21-1 and TB21-2 on VR22. Is reference voltage across 1 & 2 20 VAC or more? | Proceed to step 14 if YES; proceed to step 13 if NO | |
| No build up of AC output voltage — Is exciter field voltage across F1+ and F2- on endbell terminal block 7.0 VDC or more? | Wiring harness W9 from end bell to VR22 terminals 3 and 4 may be faulty | If not, check wiring harness W9 from end bell to VR22 terminals 3 and 4 |
| No build up of AC output voltage — Are diodes CR1, CR2, CR3, CR4, CR5, CR6 in rotating rectifier assemblies OK? | Defective diode(s) — check all diodes, more than one may be defective | |
| No build up of AC output voltage — Flash exciter field. Is reference voltage across 1 and 2 now 20 VAC or more? | Proceed to step 14 if YES; proceed to step 13 if NO | |
| No build up of AC output voltage — Reconnect generator leads 1 & 2 to TB21-1 and TB21-2 on VR22. Does reference voltage build up? | Proceed to step 15 if YES; proceed to step 13 if NO | |
| No build up of AC output voltage — Is regulator DC output voltage across VR21-7 and VR21-8 7 VDC or more? | Proceed to step 16 if YES; proceed to step 18 if NO | |
| No build up of AC output voltage — Are SCR's CR13 and CR16 OK? | Proceed to step 17 if YES; proceed to step 18 if NO | |
| No build up of AC output voltage — Are diodes CR12, CR14, and CR15 OK? | Proceed to step 18 if YES; proceed to step 18 if NO | |
| No build up of AC output voltage — Replace voltage regulator PC board (VR21) | Replace voltage regulator PC board (VR21) | |
| AC output voltage builds up, but is unstable — Are there any loose or broken wires or connections on voltage regulator assembly VR22? | Loose or broken wires or connections on voltage regulator assembly VR22 | Proceed to step 2 if YES; proceed to step 2 if NO |
| AC output voltage builds up, but is unstable — Is W9 (exciter field) wiring harness from VR22 to End bell OK? | Proceed to step 3 if YES; proceed to step 4 if NO | |
| AC output voltage builds up, but is unstable — Does adjustment of Damping Control R27 potentiometer on VR21 result in stable voltage? | Proceed to step 4 if YES; proceed to Test Procedure A if NO | |
| AC output voltage builds up, but is unstable — Replace | Replace | |
| Engine does not crank — Check 12 VDC to ground at battery BT1 and at starter motor B1. Check B+ present at TB11, K11, K13, S1, and M11. | Proceed to step 2 if YES; proceed to Test Procedure A, G if NO | |
| Engine does not crank — Is battery dead? Check if centrifugal switch S1 is open to ground. If S1 remains closed when set is shutdown, R11 and K14 will discharge through S1 to ground. Remove switch cover and check operation manually. | Centrifugal switch S1 remains closed when set is shutdown, causing R11 and K14 to discharge through S1 to ground | Remove switch cover and check operation manually |
| Engine does not crank — Replace S1. Replace or charge battery. | Replace S1; Replace or charge battery | |
| Engine does not crank — Jumper battery cable connection to ground at starter. Does engine crank? | Proceed to step 6 if YES; proceed to step 7 if NO | |
| Engine does not crank — Check starter motor. Repair or replace. | Starter motor faulty | Repair or replace |
| Engine does not crank — With S11 at START, is at least 7 volts present between terminal S on K11 and ground. Does K11 energize? | Proceed to step 8 if YES; proceed to step 10 if NO | |
| Engine does not crank — Does manual operation of K11 crank engine? | Proceed to step 9 if YES; proceed to step 10 if NO | |
| Engine does not crank — Jumper K11 from B+ to S terminal. Does engine crank? | Proceed to step 10 if YES; proceed to step 11 if NO | |
| Engine does not crank — Start relay K11 is defective; replace. | Start relay K11 defective | Replace |
| Engine does not crank — With S11 at START, jumper K11 contacts to starter solenoid. Does engine crank? | Proceed to step 11A if YES; proceed to step 12 if NO | |
| Engine does not crank — Replace K11. | Replace K11 | |
| Engine does not crank — With S11 at START, jumper normally closed contacts of K12. Does engine crank and start? | Proceed to step 13 if YES; proceed to step 10 if NO | |
| Engine does not crank — Replace K12. | Replace K12 | |
| Engine cranks but does not start — Is 12 VDC present between start terminal on S11 and ground (TB11-1) with S11 at START? | Proceed to step 2 if YES; proceed to Test Procedure G if NO | |
| Engine cranks but does not start — Is 12 VDC present between M11-B+ and ground TB11-1 with S11 at START? Check Wire W3 & W8. | Proceed to step 3 if YES; proceed to step 4 if NO | |
| Engine cranks but does not start — Replace faulty switch S11. | Faulty switch S11 | Replace faulty switch S11 |
| Engine cranks but does not start — Does engine operate on gasoline? Is fuel primer solenoid K3 energized when S11 is at START? | Proceed to step 6 if YES; proceed to step 9 if NO | |
| Engine cranks but does not start — Remove fuel solenoid from fuel line and press S11. Does fuel pulsate from line? | Proceed to step 9 if YES; proceed to step 12 if NO | |
| Engine cranks but does not start — Check lead from TB12-4 to fuel pump; check fuel pump and replace if necessary. | Faulty fuel pump or lead from TB12-4 to fuel pump | Check lead from TB12-4 to fuel pump; check fuel pump and replace if necessary |
| Engine cranks but does not start — Check engine oil level. If okay, remove LOP switch S4 lead at TB12-4. Does engine crank and run when S11 is pressed? | Proceed to step 11 if YES; proceed to step 13 if NO | |
| Engine cranks but does not start — Is lead 6 from TB12-6 to LOP switch S4 grounded? | Proceed to step 12 if YES; proceed to Test Procedure G if NO | |
| Engine cranks but does not start — Repair or replace lead 6 to S4. | Lead 6 to S4 faulty | Repair or replace lead 6 to S4 |
| Engine cranks but does not start — If necessary, replace LOP switch S4. | If necessary, replace LOP switch S4 |
Fault codes and symptom→remedy steps extracted from this model’s service/owner documentation; verify against the official manual before servicing.
Documented causes: Poor compression, usually due to worn piston, rings, or cylinder; Oil leaks from oil base or connections. This does not cause smoky exhaust; Oil too light or diluted; Worn engine. See the table for the matching fixes.
Documented causes: Defective gauge; Oil too light or diluted from leaking fuel pump diaphragm; Oil too low; Oil relief valve not seating. See the table for the matching fixes.
Documented causes: Battery discharged; Loose connections; Defective starting circuit; Defective starting motor on revolving field generator. See the table for the matching fixes.