Cummins QSB6.7 Troubleshooting
| Engine Model: Cummins QSB6.7 |
| Engine Type: 4-cycle inline 6-cylinder common-rail direct injection liquid-cooled diesel |
| Total Displacement: 409 cu.in (6.7 L) |
| Rated Engine Power: 160-300 Hp (119-224 kW) at 2200 rpm |
| Aspiration Type: Turbocharged |
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| Engine difficult to start or doesn't start |
Clogged fuel filter - Change filter element.
Air in the fuel system - Air bleeding.
Fuel injection nozzles are clogged or faulty - If necessary, replace with a new nozzle.
Fuel injection pump failure - Replace injection pump or repair it.
Valve timing is improper - Correct or replace timing gear.
Dirt in the fuel lines or hoses - Clean or replace fuel pipes.
Improper injection timing - Adjust injection timing as required.
Damaged piston rings and cylinder - Change faulty components.
| Diesel starts and stalls immediately |
Fuel filter element is dirty - Replace filter element.
Fuel injection pump malfunction - Repair or replace injection pump.
Air cleaner is dirty - Air filter maintenance required.
Nozzle opening pressure is incorrect - Set it correctly.
| Diesel shuts off while driving |
Fuel injection timing is wrong - Use the correct fuel injection pump timing adjustment.
Dirty fuel filter - Change the filter element.
Engine is not fully warmed up - Engine is not warmed up to the required temperature.
Stuck or clogged injection nozzle - Repair or replace injection nozzles.
| Engine stops while idling |
Incorrectly adjusted low idle speed - Adjustment required.
Valve clearance is not correct - Adjust to proper valve clearance.
Defective fuel injection pump - Repair or install new pump.
Fuel injection nozzles are dirty or defective - Clean or replace injection nozzles.
Fuel hoses or lines are clogged - Clean fuel system lines and hoses.
Dirty air filter - Service or replace the air filter.
Cylinder head gasket is damaged - Gasket should be replaced.
Incorrect injection timing - Adjust according to specifications.
Fuel injection pump failure - Replacement or repair required.
One of moving engine parts has broken - Repair or replace defective components.
Clogged radiator fins or damaged radiator cap - Clean radiator or change cap.
Lack of coolant in cooling system - The cooling system needs to be refilled and checked for faults.
Loose or damaged fan belt - Install new fan belt.
Lack of engine oil - Fill the crankcase with engine oil.
Cylinder-head gasket is leaking - Cylinder-head gasket replacement required.
Injection timing is incorrect - Adjust injection timing as required.
| Oil pressure is insufficient |
Not enough oil in the engine - Need to add oil.
Oil pump failure - Remove and inspect oil pump.
Oil filter clogged - Service or replace engine oil filter.
Relief valve is defective or dirty - Replace or service relief valve.
Clearance of crankshaft bearing is excessive - Test and repair or replace worn parts.
Clearance of crankpin bearing is excessive - Test and repair or replace worn parts.
| Engine consuming too much oil |
Oil leaking: Worn seals or gaskets - Replace worn parts to avoid leaks.
Wrong oil viscosity - Use proper viscosity oil.
Worn or broken piston rings - Replace piston rings.
Damaged valve guides or valve stems - Change the valves.
Scuffed cylinder liners or pistons - Inspect liners and pistons, replace as necessary.
Engine has not warmed up to the recommended temperature - Warm up to required temperature.
Not enough engine oil - Fill the crankcase with engine oil.
Improper fuel injection timing - Set the fuel pump timing correctly.
Pistons are broken or worn - Pistons replacement required.
Connecting rod is worn or not aligned - Need to change or align the connecting rod.
Low battery output voltage - Charge the battery.
Battery runs out quickly - Service battery or replace it.
Battery terminals are corroded or wires are disconnected - Check battery wires and service or replace terminals.
Battery is low or faulty - Battery needs to be recharged or replaced.
Wiring is improperly connected or disconnected - Check wiring and connect properly.
Low battery power - Charge the battery.
Damaged starter motor - Starter needs to be replaced.
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