The Box (Onan) is a generator-set controller. It is used on generator sets from Cummins/Onan, including the 10CW.
| Symptom | Cause | Remedy |
|---|---|---|
| BLACK, SMOKY EXHAUST, EXCESSIVE FUEL CONSUMPTION, FOULING OF SPARK PLUGS WITH BLACK SOOT, POSSIBLE LACK OF POWER UNDER HEAVY LOAD | Fuel mixture too | |
| Brushes worn excessively or making poor contact. | Engine will not start when cranked. | Replace brushes or clean commutator. |
| Choke not fully open | See that choke opens properly. Adjust jets properly. Adjust the float level. | |
| Clean, adjust, or replace breaker points, spark plugs, condenser, etc., or retime ignition. | Engine will not start when cranked. | Faulty ignition. |
| Corroded battery terminals. | Engine cranks too slowly when cranked electrically. | |
| Cylinders flooded. | Engine will not start when cranked. | Poor fuel. Drain. Refitl with good fuel. |
| DULL METALLIC THUD, IF NOT BAD, MAY DISAPPEAR AFTER FEW MINUTES OF OPERATION. IF BAD, INCREASES WITH LOAD | Replace, unless one of the next two remedies permanently corrects the trouble. Loose crankshaft bearing. | |
| Dirty air cleaner | Clean and Service. | |
| Dirty or corroded points in starter solenoid switch. | Engine will not start when cranked. | Replace switch. |
| Discharged or defective battery. | Engine cranks too slowly when cranked electrically. | Recharge or replace. Tighten loose connections. |
| Dull metallic thud, if not sag, may disappear after few minutes operation. 1 F Bad, increases with load | Loose crankshaft bearing. Replace, usually one of the next two remedies per manfacturerly corrects the trouble. | |
| ENGINE BACKFIRES | Lean fuel mixture. Clogged fuel filter. Air leak at intake manifold or carburetor flange. Poor fuel. Spark advanced too far. Intake valve leaking. | |
| ENGINE CRANKS TOO SLOWLY WHEN CRANKED ELECTRICALLY | Discharged or defective battery. Loose connections. Crowded battery terminals. Brushes worn excessively making poor contact. Short circuit in generator load circuit. Pasty of corroded points in start solenoid switch. | Recharge or replace. Tighten loose connections. Clean crowded terminals. Replace cable if necessary. Replace brushes or clean commutator. Repaie or replace parts necessary. Disconnect load. Replace Switch. |
| ENGINE CRANKS TOO STIFFLY | Too heavy oil in crankcase. Engine stuck. | Drain. Refill with light oil. Disassemble and repaiz. |
| ENGINE MISFIRES AT ALL LOADS | Fouled spark plug. Defective or wrong spark plug. Leaking valves. Broken valve spring. Defective or improperly adjusted breaker points. | Clean and adjust. Adjust of replace breaker points. |
| ENGINE MISFIRES AT HEAVY LOAD | Defective spark plug. Faulty ignition. Clogged carburetor. Clogged fuel screen. Defective spark plug cable. | Replace. Clean, adjust, or replace breaker points, spark plugs, condenser etc., or retime ignition. Clean carburetor. Clean. Reglace. |
| ENGINE MISFIRES AT LIGHT LOAD | Carburetor idle jet clogged or improperly adjusted. Spark plug gaps too narrow. intake air leak. Faulty ignition. | Clean or adjust. Adjust ‘to correct gap -025” (.018” for gas operation). Tighten manifold and carburetor mounting screws, Replace gaskets if necessary. Clean, adjust, or replace breaker points, spark plugs, condenser, etc. or retime ignition. |
| ENGINE OVERHEATING | Improper lubrication. Spar ventilation. Dirty or oily cooling surfaces. Retarded ignition timing. Generator overloaded. | See Low Oil Pressure. Provide ample ventilation at all times. Keep the engine clean. Retime ignition. Reduce load. |
| ENGINE RUNS GUT VOLTAGE GOES NOT BUILD UP | Poor brush contact. Open circuit, short circuit, or ground in generator. | See that brushes seat well on commutator and collector rings, are free in holders, are not worn shorter than 1/2-inch, and have good spring tension. Refer to the GENERATOR section of Maintenance. |
| ENGINE WILL NOT START WHEN CRANKED | Faulty ignition. Lack of fuel or faulty carburetion. Cylinders flooded. Poor fuel. Poor compression. | Clean, adjust, or replace points, spark plugs, condenser, etc., or retine ignition. Refill the tank. Check the fuel system. Clean, adjust, or replace parts necessary. Ground spark plug cables. Crank engine with spark plugs removed. Drain. Refill with good fuel. Tighten cylinder heads and spark plugs. Uf still not corrected, grind the valves. Replace piston ings if necessary. |
| EXCESSIVE CIL CONSUMPTION, LIGHT BLUE EXHAUST | Poor compression. Usually due to worn piston, rings, or cylinders. Oil too light or diluted. Too large bearing clearance. Oil seal leaks. | |
| EXCESSIVE DIL CONSUMPTION. LIGHT BLUE EXHAUST | Poor compression. Usually due to wom pistons, rings, or cylinders. | Refinish cylinders. Install oversize pistons and rings. |
| EXCESSIVE OIL CONSUMPTION, LIGHT BLUE EXHAUST (Cont.) | Refer to 'Engine Misfires At All Loads'. Engine misfires. Faulty ignition. Clean, adjust, or replace breaker points, spark plugs, condenser, etc., or retime the ignition. Too much oil. Drain excess oil. | |
| Engine stops unexpectedly | Empty fuel tank. Check the ignition system. Repair or replace as needed. See that the STOP button lead is set grounded. | |
| Excessive arcing of brushes | Rough commutator or rings. Dirty commutator or rings. Brushes not seating properly. Open circuit in armature. Brush cig out of position. Turn down. Clean. Sand to a good seat of reduce load until worn in, install a new armature. Line up properly. | |
| Fluctuating load. | Engine runs but voltage does not build up. | Correct any abnormal load condition causing trouble. |
| GENERATOR OVERHEATING | Short in load circuit. Generator overloaded. Improper brush rig position. | Correct short circuit. Reduce the load. Refer to the GENERATOR section of MAINTENANCE — See Brush Rig. |
| Ground spark plug cables. | Engine will not start when cranked. | Crank engine with spark plugs removed. |
| HIGH OF PRESSURE | Oil too heavy. Clogged oil passage. Dil relief valve stuck. Mefective oil pressure gauge. | Drain, refill with proper oii. Clean all lines and pas sages. Remove and cleaa. Replace. |
| HIGH OIL PRESSURE | Oil too heavy. Clogged oil passage. Dil relief valve stuck. Mefective oil pressure gauge. | Drain, refill with proper oil. Clean all lines and pas sages. Remove and cleaa. Replace. |
| Hollow clicking sound with cool engine under load | Loose piston. If noise is only slight and disappears when engine warms up, no immediate attention needed. Otherwise replace parts necessary. | |
| LOW OIL PRESSURE | Oil too light. OH badly diluted. Oil teo low. ODl reef valve aot seating. Badly worn bearings. Sludge on oil screen. Badly worn oi} pump. Defective oi] pressure gauge. | Drain, refill with proper oil. Drain, reGill with proper oil. Add oil. Remove and clean, or re- eplace. Replace. Remove and clean. Replace. Replace. |
| Lack of fuel or faulty carburetion. | Engine will not start when cranked. | Refill the tank. Check the fuel system. Clean, adjust, or replace parts necessary. |
| Loose connections. | Engine cranks too slowly when cranked electrically. | Clean corroded terminals. Replace cable if necessary. |
| Motors run too slowly and overheat at far end of line but ok hear the plant | Too small wire used for load fastall larger or extra wires of reduce load. | |
| Noisy brushes | High mica between bars of commutator. Undercut mica. Adjust to proper clearance. See VALVE TAPPETS. | |
| Oil dilution | One spark plug fouled. Leaky carburetor valve. Clean plugs. Clean. Tighten — replace if gasket is damaged. | |
| Pinging sound when engine is suddenly or heavily loaded | Carbon in cylinders. Spark advanced too far. Wrong spark plugs. Spark plugs burned or carboned. Valves hot. Fuel stale or low octane. Lean fuel mixture. Remove the carbon. Reset breaker points or retime ignition. Replace faulty spark plugs. Clean. Install new plugs if necessary. Adjust tappet clearance, see VALVE SERVICE. | |
| Poor brush contact. | Engine runs but voltage does not build up. | Open circuit, short circuit, or ground in generator. See that brushes seat well on commutator and collector rings, are free in holders, are not worn shorter than 1/2 inch, and have good spring tension. |
| Poor compression. | Engine will not start when cranked. | Stop circuit closed. Check switch. |
| Sharp click when cranking engine | Normal condition — should stop as soon as engine starts. Magneto impulse coupling. | |
| Sharp metallic thud, especially when cold engine first started | Low oil supply. Oil badly diluted. Add oil. Change if necessary. | |
| Short circuit in generator load circuit. | Engine will not start when cranked. | Repair or replace parts necessary. Disconnect load. |
| Short in load circuit. | Generator overheating. | |
| Spark plugs foul rapidly | Engine running “cold”. Wrong plugs. Carburetor too “rich”. Restrict air flow. Install preheater hose. Replace with correct plugs. Adjust. | |
| Speed too low. | Engine runs but voltage does not build up. | Adjust governor to correct speed. |
| Tapping sound | Valve clearance too great. Broken valve spring. Install new spring. | |
| Tighten cylinder heads and spark plugs. | Engine will not start when cranked. | If still not corrected, grind the valves. Keplacc piston rings if necessary. |
| Too heavy oil in crankcase. | Engine cranks too stiffly. | Drain. Refill with light oil. |
| VOLTAGE DROPS UNDER HEAVY LOAD | Engine lacks power. Poor compression. Faulty carburetion. Dirty carburetor air cleaner. Choke partly closed. Carbon in cylinders or in carburetor venturi. Restricted exhaust line. improper governor adjustment. | See remedies under ‘'Ea- gine Misfires at Heavy Load”. |
| VOLTAGE UNSTEADY BUT ENGINE NOT NISFIFUNG | Speed too low. Poor commutation or brush contact. Loose connections. Fluctuating load. | Adjust govemor to correct speed. Refinish commutator or undercut mica if necessary, See that brushes seat well on commutator and collector rings, are free in holders, are not worn shorter than 1/2-inch, and have good spring tension. Tighten connections. Correct any abnormal load condition causing trouble. |
| Voltage low at far end of line but normal near plant | Too small line wire used for load and distance. Install larger or extra wires or reduce load. |
Fault codes and symptom→remedy steps extracted from this controller’s service/owner documentation; verify against the official manual before servicing. Aggregated from the service documentation of generator sets built on this controller.