Cummins 6B5.9 Troubleshooting
| Engine Model: Cummins 6B5.9 |
| Engine Type: 4-cycle inline 6-cylinder direct-injection liquid-cooled diesel |
| Total Displacement: 359 cu.in (5.9 L) |
| Rated Engine Power: 80-135 Hp (60-100 kW) at 2300 rpm |
| Aspiration Type: Naturally aspirated |
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| Engine starts hard or doesn't start |
Fuel filter element is dirty - Clean or change the filter.
Air in fuel system - Bleed fuel system.
Dirty or faulty injection nozzles - Service or change injection nozzles.
Fuel injection pump malfunction - Rebuild or install a new injection pump.
Wrong valve timing - Adjust or change timing gear.
Plugged fuel pipes - Clean or replace fuel pipes.
Unadjusted injection timing - Adjust as recommended.
Worn piston rings and cylinder - Change faulty components.
| Engine stalls after starting |
Dirty fuel filter - Replace the filter element.
Defective fuel injection pump - Install a new fuel pump or repair.
Plugged air cleaner - Clean or replace the element.
Nozzle opening pressure is improper - Set it correctly.
| Engine shuts off suddenly while running |
Improper fuel injection timing - Adjust the pump as required.
Fuel filter plugging - Change the filter element.
Engine is not fully warmed up - Engine is not warmed up to the required temperature.
Defective or stuck injection nozzles - Clean or change injection nozzles.
Incorrect low idle setting - Adjust low idle speed.
Excessive valve clearance - Check and adjust.
Fuel injection pump damage - Replace injection pump or repair it.
| Diesel engine loses power |
Dirty or faulty injection nozzles - Install a new kit of correctly balanced nozzles.
Clogged fuel lines or hoses - Fuel hoses and lines must be clean.
Clogged air filter element - Air filter maintenance required.
Cylinder head gasket is damaged - Change cylinder head gasket.
Injection timing is out of adjustment - Check injection timing adjustment.
Fuel injection pump is defective - Replace or rebuild injection pump.
One of moving engine components has failed - Repair or replace defective components.
Clogged radiator fins or leaking radiator cap - Clean radiator or change cap.
Lack of engine coolant - Refill to the correct level and inspect system for leaks.
Damaged or worn fan belt - Replace the fan belt.
Engine oil insufficient - Check oil level and add oil as required.
Cylinder head gasket is worn - Change cylinder head gasket.
Incorrect injection timing - Adjust as recommended.
| Insufficient oil pressure |
Oil level is low - Fill the crankcase with oil.
Defective oil pump - Remove and inspect oil pump.
Clogged oil filter - Change or service engine oil filter.
Relief valve is seized or worn - Change or service relief valve.
Clearance of crankshaft bearing is excessive - Check and change or repair defective parts.
Excessive oil clearance of crankpin bearing - Check and replace or repair defective parts.
| Excessive oil consumption |
Oil leakage: Seals or gaskets are defective - Replace defective parts.
Crankcase oil too light - Use oil of proper viscosity.
Worn or stuck piston rings - Change piston rings.
Valve guides and stems are worn - Install new valves.
Pistons or cylinder liners are damaged - Inspect liners and pistons, replace as necessary.
| Abnormal engine noise or knocking |
Engine is not warmed up to the required temperature - Warm up the engine.
Insufficient engine oil - Fill the crankcase with engine oil.
Fuel injection pump timing is not adjusted - Set up as recommended.
Worn or broken pistons - Have pistons replaced.
Connecting rod misalignment or failure - Need to replace or align the connecting rod.
Battery power is low - Charge the battery.
Battery is not holding charge - Service charging system or install new battery.
Bad terminals or disconnected battery cables - Connect wiring correctly or install new terminals.
Battery is discharged or worn - Need to charge or replace the battery.
Disconnected or incorrectly connected wires - Inspect battery wires and connect correctly.
Low battery output - Battery needs to be recharged.
Starter motor is defective - Starter needs to be replaced.
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