Mitsubishi 6D31 Troubleshooting
| Engine Model: Mitsubishi 6D31 |
| Engine Type: 4-cycle inline 6-cylinder liquid-cooled diesel |
| Total Displacement: 302 cu.in (4.95 L) |
| Rated Engine Power: 105-120 Hp (78-89 kW) at 2900 rpm |
| Fuel System Type: Direct injection |
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| Engine starts hard or won't start |
Dirty fuel filter - Replace filter element.
Air in the fuel pipes - Bleed the fuel pipes.
Faulty fuel injection nozzles - Change fuel injection nozzles.
Fuel injection pump is not operating properly - Install a new pump or rebuild.
Wrong valve timing - Adjust or change timing gear.
Fuel pipes are plugged - Clean or change fuel pipes.
Improper injection timing - Set the injection timing correctly.
Worn cylinder or piston rings - Change faulty parts.
Fuel filter element is clogged - Clean the filter element.
Fuel injection pump is faulty - Repair or replace injection pump.
Air cleaner is dirty - Clean or change the filter.
Nozzle opening pressure is not adjusted - Set up as recommended.
| Engine shuts off while running |
Improper fuel injection timing - Set it up as required.
Fuel filter element clogging - Service the filter.
Engine is cold - Warm up the engine.
Stuck or burnt injection nozzle - Change or repair injection nozzles.
Too low idle RPM - Test and adjust.
The valve clearance is incorrect - Adjustment procedure required.
Faulty fuel injection pump - Change or repair the pump.
Fuel injection nozzles are dirty or defective - Clean or change injection nozzles.
Dirt in the fuel lines or hoses - Fuel lines and hoses need to be cleaned.
Plugged air cleaner - Service air cleaner.
Defective cylinder head gasket - Replace cylinder head gasket.
Injection timing is incorrect - Set the injection timing correctly.
Fuel injection pump is damaged - Repair or install new pump.
Any of moving engine components is faulty - Repair or replace defective parts.
Dirty radiator fins or defective radiator cap - Install new cap or clean radiator.
Coolant level is low - Add coolant and check the components of cooling system.
Damaged or worn fan belt - Change the fan belt.
Insufficient engine oil - Check and refill engine oil.
Defective cylinder head gasket - Install a new gasket.
Unadjusted injection timing - Set the injection timing correctly.
| Oil pressure is insufficient |
Engine oil level low - Fill the crankcase with oil.
Oil pump failure - Repair or change.
Dirty oil filter - Service or replace engine oil filter.
Stuck or worn relief valve - Relief valve need to be replaced or cleaned.
Excessive oil clearance of crankshaft bearing - Check and change or repair defective parts.
Excessive oil clearance of crankpin bearing - Inspect and replace or repair faulty components.
| Excessive oil consumption |
Oil leaking: Worn seals or gaskets - To repair leaks, replace worn parts.
Crankcase oil too light - Use oil of correct viscosity.
Worn or broken piston rings - Change piston rings.
Damaged valve guides or valve stems - Install new valves.
Cylinder liners or pistons are damaged - Check pistons and liners, install new parts as required.
| Abnormal engine noise or knocking |
Coolant temperature is low - Warm up the engine.
Insufficient engine oil - Fill up the oil to required level.
Fuel injection pump timing is wrong - Adjust the pump as required.
Piston wear or scoring - Replace the pistons.
Connecting rod is worn or not aligned - Need to align or replace the connecting rod.
Battery capacity is low - Battery is drained, charge it.
Battery does not hold charge - Service charging system or change battery.
Disconnected wiring or bad battery terminals - Check wire connections and change or service terminals.
Battery is discharged or defective - Change or recharge battery.
Disconnected or improperly connected wiring harness - Inspect battery wiring harness and connect as required.
Low battery power - Battery needs to be recharged.
Starter motor is defective - Starter should be replaced.
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