Mitsubishi 4DQ50 Troubleshooting
| Engine Model: Mitsubishi 4DQ50 |
| Engine Type: 4-cycle inline 4-cylinder naturally aspirated liquid-cooled diesel |
| Total Displacement: 127.2 cu.in (2.08 L) |
| Rated Engine Power: 55 Hp (40 kW) at 2500 rpm |
| Fuel System Type: Indirect injection |
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| Engine starts hard or doesn't start |
Clogged fuel filter - Clean the filter or install new filter element.
Air in fuel tank - Bleed fuel tank.
Faulty fuel injection nozzles - Clean or change injection nozzles.
Fuel injection pump failure - Repair or replace injection pump.
Improper valve timing - Use correct valve timing adjustment.
Fuel pipes clogging - Clean or change fuel pipes.
Wrong injection timing - Adjust injection timing as required.
Cylinder or piston rings are worn - Replace faulty parts.
| Diesel starts but then stops |
Fuel filter plugged - Install new filter element.
Faulty fuel injection pump - Replace or repair injection pump.
Restricted intake air - Air filter maintenance required.
Unadjusted nozzle opening pressure - Adjust according to specifications.
| Diesel shuts off while driving |
Fuel injection timing is not adjusted - Adjust as recommended.
Dirty fuel filter - Replace the filter element.
Low coolant temperature - Warm up to required temperature.
Stuck or clogged injection nozzle - Service or change injection nozzles.
Incorrect low idle speed adjustment - Adjustment required.
Valve clearance is out of adjustment - Adjust to proper valve clearance.
Fuel injection pump is damaged - Rebuild or install a new injection pump.
Damaged or dirty injection nozzles - If necessary, replace with a new nozzle.
Fuel lines or hoses clogging - Service fuel lines and hoses.
Air cleaner is dirty - Change air filter element.
Cylinder-head gasket is leaking - Gasket should be replaced.
Wrong injection timing - Set the injection timing correctly.
Fuel injection pump is faulty - Repair or replace injection pump.
Any of moving engine parts is worn - Replace or repair damaged components.
Dirty radiator core or faulty radiator cap - Clean radiator or replace cap.
Insufficient coolant fluid - Add coolant fluid to cooling system and also check it for leaks.
Broken or loose fan belt - Change as required.
Engine oil insufficient - Check and refill engine oil.
Defective cylinder head gasket - Replace the gasket as required.
Injection timing is out of adjustment - Adjust as recommended.
| Insufficient oil pressure |
Engine oil level low - Fill the crankcase with oil.
Oil pump malfunction - Install a new pump.
Oil filter clogging - Change or clean engine oil filter element.
Stuck or defective relief valve - Replace or clean relief valve.
Excessive crankshaft bearing clearance - Check and replace or repair defective parts.
Crankpin bearing clearance is excessive - Check and replace or repair defective parts.
| Excessive oil consumption |
External oil leaks: Defective seals or gaskets - Worn parts need to be replaced.
Crankcase oil too light - Use correct viscosity oil.
Worn or broken piston rings - Change piston rings.
Worn valve stems and valve guides - Install new valves.
Pistons or cylinder liners are scuffed - Check liners and pistons, replace as required.
| Abnormal engine noise or knocking |
Engine is not warmed up to the required temperature - Warm up engine as required.
Engine oil level low - Check oil level and add oil as required.
Fuel injection pump timing is wrong - Adjust fuel injection pump as required.
Piston wear or scoring - Replace the pistons as required.
Faulty or misaligned connecting rod - Need to replace or align the connecting rod.
Battery voltage is low - Charge the battery.
Battery runs out quickly - Service charging system or change battery.
Disconnected battery cables or bad terminals - Check wiring and clean or replace terminals.
Battery is drained or worn - Charge or replace the battery.
Wiring harness is disconnected or improperly connected - Check wiring harness and connect as required.
Battery power is low - Battery needs to be recharged.
Starter motor is damaged - Repair or install a new starter.
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