Cummins/Onan MDKAD troubleshooting: 43 symptom-cause-remedy entries from the manufacturer's own service documentation.
Cummins/Onan MDKAD — full specs, parts & maintenance.
All Cummins/Onan fault codes →
| Symptom | Cause | Remedy |
|---|---|---|
| Engine does not crank | Open circuit breaker CB1, CB2 or CB4 | Check to see if breaker is accidentally tripped; Check and correct fault conditions that might trip breakers: CB1: check shorts to ground on/near glow plug circuits; CB2: check and correct fault conditions sensed by engine fault sensors: S2: high engine temperature, S3: low coolant level, S4: low oil pressure, S5: high exhaust temperature; CB2: check possible shorted fault sensors S1, S2, S3, S4; CB4: check K7 stop solenoid for adjustment |
| Engine does not crank | No B+ voltage to starter | Check B+ and ground connections at battery and grounding point on engine; Check battery cables per Checkout B (Section 3 of manual); Check B+ voltage while cranking at SW terminal on starter (TB2-11): is there voltage while pressing Start switch? Yes: problem is in starter or solenoid; No: problem is in control circuit |
| Engine does not crank | Starter is not functional | Remove starter from genset, check and replace if necessary |
| Engine does not crank | Battery is not functional | Check battery per Checkout A (Section 3 of manual) and recharge or replace; Check battery charger operation per Checkout C (Section 3) |
| Engine does not crank | Start relay K1 is not functional | Check relay per Checkout D (Section 3), replace if bad; Check K7 stop solenoid for adjustment |
| Engine cranks but does not start | Fuel is not getting to the engine | Check fuel pump per Checkout H (Section 3); Place meter on fuel pump terminal and press Start switch: is voltage reaching fuel pump?; Test fuel tank level, shutoff valves, fuel lines and connections, fuel filters, injection pump; Air in fuel lines: prime fuel system |
| Engine cranks but does not start | Glow plugs not operating correctly | Check/replace individual glow plugs per instructions in Engine Manual; Place meter on glow plug terminal and press Preheat switch: is voltage reaching glow plug?; Test K5 glow plug relay per Checkout E (Section 3); Test continuity of K5 circuit; Test Start/Stop-Preheat switch per Checkout G (Section 3) |
| Engine cranks but does not start | Fuel shutoff solenoid not operating correctly | Place meter on fuel solenoid terminal and press Start switch: is voltage reaching fuel solenoid?; Test fuel solenoid circuit for continuity through B+; Disconnect fuel solenoid from circuit, test per Checkout F (Section 3). Adjust/replace as necessary. |
| Engine starts but stops after several seconds | Fault conditions cause fault breaker CB2 to open | CB2: check and correct fault conditions sensed by engine fault sensors: S2: high engine temperature: check water pump operation; S3: low coolant level; S4: low oil pressure; S5: high exhaust temperature; Check possible overspeed conditions; Engine speed set too high: reset to 1500 or 1800 rpm according to instructions in Section 4 of manual; Voltage regulator board 50/60 Hz switch is set at 50 Hz while governor lever is set at 60 Hz: both settings must be the same; Check all B+ wiring for shorts to ground |
| Engine starts but stops after several seconds | Fuel pump is stopped or intermittent | Check fuel pump per Checkout H in next section of manual: replace if necessary; Check fuel pump circuit for continuity |
| Engine starts but stops after several seconds | Air in fuel line | Prime fuel system (press S1 to the STOP position) |
| Engine starts and runs but remains running only while start switch is held | If there is AC output from the set: K4 relay may not be changing state | Remove K4, check per Checkout E (Section 3): replace if necessary; Check K4 wiring for continuity |
| Engine starts and runs but remains running only while start switch is held | If there is no AC output from the set: generator/voltage regulator may be at fault (not control system) | Check generator/voltage regulator per procedures in Sections 5 and 6 of manual |
| No AC output voltage at rated engine RPM | Load circuit breakers not closed | Close circuit breakers, or replace if bad. If voltage is unstable, high or low, or causes breaker to trip, see Flow Charts B or C. |
| No AC output voltage at rated engine RPM | Residual voltage across L1 and L2 not 14 VAC ± 5 VAC (TEST [A]) | Flash exciter field per TEST [B]. Does generator output voltage build up? |
| No AC output voltage at rated engine RPM | After flashing field, output voltage does not build up | Disconnect J2/P2 connection to voltage regulator. Is residual voltage across L1 and L2 14 VAC ± 5 VAC now? |
| No AC output voltage at rated engine RPM | Residual voltage not present with J2/P2 disconnected | Generator stator is OK. Check exciter rotor and stator wiring per TESTS [F] and [G]. Check exciter field wiring for shorts per TEST [J]. Replace bad wiring. Check lead continuity per TEST [J]. Check diodes CR1 through CR6 on rotor per TEST [E]. Replace if bad. Check exciter rotor winding per TEST [G]. Replace if bad. Check generator rotor winding per TEST [I]. Replace if bad. Check generator stator windings per TEST [H]. Replace if bad. |
| No AC output voltage at rated engine RPM | Residual voltage present with J2/P2 disconnected | Is exciter field voltage at (J2/P2 pins 8 and 1) approximately 6.5 VAC (60 Hz sets) or volts ± 10 VAC? Yes: AVR should be OK. Check exciter rotor winding per TEST [G]. Replace if bad. No: Check exciter field wiring for shorts per TEST [J]. Check voltage regulator per TEST [C]. |
| Unstable voltage, engine speed stable | Broken wires or loose connections on voltage regulator assembly | Check wiring harness from regulator assembly to end bell per TEST [J]. Check OK? Yes: Replace the voltage regulator per procedure (D). No: Repair as required. Repair wiring or replace as required. |
| Unstable voltage, engine speed stable | Engine not running at correct RPM | Set RPM per instructions in appropriate engine manual. |
| Unstable voltage, engine speed stable | Adjustment of Voltage Adjust control on the regulator board does not result in correct output voltage | Set control per Voltage Adjustment [K]. |
| Unstable voltage, engine speed stable | Voltage regulator connections not secure | Check/retighten/replace voltage regulator connections. |
| Unstable voltage, engine speed stable | Generator output leads not properly connected | See TEST [L]. Replace the voltage regulator per procedure [D]. |
| Unbalanced generator output voltage | Output still unbalanced with load removed at generator terminals | Are generator leads connected and grounded properly? See Test [L]. Is generator stator winding continuous per TEST [H]? Yes: Replace stator assembly. No: Check for correct grounding of generator and load. Correct as necessary. |
| Unbalanced generator output voltage | Output balanced with load removed (load fault) | Check load for ground faults and correct as necessary. |
| Engine does not crank from remote panel | Emergency Stop Switch OFF | Push ON. |
| Engine does not crank from remote panel | “Check Generator” or “Check Engine” Fault | Service the fault as necessary and push fault reset button in. See “CHECK ENGINE” FAULT SHUTDOWN or “CHECK GENERATOR” FAULT SHUTDOWN. |
| Engine does not crank from remote panel | Faulty remote circuit | Try starting at the genset control panel. If the genset starts, have the remote circuit repaired as necessary. |
| Engine does not crank from genset panel | Emergency Stop Switch OFF | Push ON. |
| Engine does not crank from genset panel | “Check Generator” or “Check Engine” Fault | Service the fault as necessary and push fault reset button in. See “CHECK ENGINE” FAULT SHUTDOWN or “CHECK GENERATOR” FAULT SHUTDOWN. |
| Engine does not crank from genset panel | Cranking voltage too low | Clean and tighten or replace the positive (+) and negative (-) battery cable connectors and cables at the battery and the genset; Recharge or replace the battery. Specific gravity for a fully charged battery is approximately 1.260 at 80° F (27° C). |
| Engine cranks but does not start | Engine not getting fuel | Open any closed shutoff valve; Check fuel level and refill as necessary; Prime the fuel system (p. 25); Check for fuel (air) leaks at all fittings and tighten as necessary; Replace the fuel filter (p. 24). |
| Engine cranks but does not start | Blocked air inlet | Service as necessary. |
| Engine cranks but does not start | Low engine temperature | Plug in, repair or install engine coolant and engine oil heaters; Replace the engine oil if it is not of the recommended viscosity for the ambient temperature. |
| Engine cranks but does not start | Cranking voltage too low | Clean and tighten or replace the positive (+) and negative (-) battery cable connectors and cables at the battery and the genset; Recharge or replace the battery. Specific gravity for a fully charged battery is approximately 1.260 at 80° F (27° C). |
| “Check Engine” Fault Shutdown | Low engine oil pressure | Check engine oil level, repair any leaks and fill to the proper level (p. 18). |
| “Check Engine” Fault Shutdown | High engine temperature | Check engine coolant level, repair any leaks and fill to the proper level (p. 19); Check V-belt tension (p. 21); Clean and service the cooling system as required to restore full cooling capacity (p. 19). |
| “Check Engine” Fault Shutdown | High exhaust temperature | Open the sea cock; Remove any blockage in the sea water strainer; Prime the sea water pump (p. 23); Replace the sea water pump impeller (p. 23); Clean seaweed and pump debris from heat exchanger (p. 23); Remove blockage covering the sea water hull strainer. |
| “Check Generator” Fault Shutdown | Generator overload. | Run with less load. |
| Engine lacks power or is unstable | Inadequate fuel delivery | Check for fuel (air) leaks at all fittings and tighten as necessary; Replace the fuel filter (p. 24). |
| Engine lacks power or is unstable | Contaminated fuel | Connect the fuel lift pump to a container of fuel of known quality. Replace the contents of the fuel supply tank if there is a noticeable difference in performance. |
| No output voltage | A line circuit breaker is Off. | Find out why the circuit breaker was turned Off, make sure it is safe to reconnect power, and then throw the circuit breaker On. |
| No output voltage | A line circuit breaker has Tripped. | Shut down the genset and have service performed as necessary to clear the short circuit or ground fault that caused tripping. Then Reset the circuit breaker and start the genset. |
Fault codes and symptom→remedy steps extracted from this model’s service/owner documentation; verify against the official manual before servicing.
Documented causes: Fuel is not getting to the engine; Glow plugs not operating correctly; Fuel shutoff solenoid not operating correctly; Engine not getting fuel. See the table for the matching fixes.
Documented causes: Open circuit breaker CB1, CB2 or CB4; No B+ voltage to starter; Starter is not functional; Battery is not functional. See the table for the matching fixes.
Documented causes: Load circuit breakers not closed; Residual voltage across L1 and L2 not 14 VAC ± 5 VAC (TEST [A]); After flashing field, output voltage does not build up; Residual voltage not present with J2/P2 disconnected. See the table for the matching fixes.