Mitsubishi S4Q Troubleshooting
| Engine Model: Mitsubishi S4Q |
| Engine Type: 4-cycle inline 4-cylinder liquid-cooled diesel |
| Total Displacement: 152.9 cu.in (2.51 L) |
| Rated Engine Power: 51 Hp (38.2 kW) at 2500 rpm |
| Fuel System Type: Indirect injection |
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| Engine starts up hard or won't start |
Fuel filter plugging - Change the filter element.
Air in the fuel pipes - Bleed the fuel pipes.
Damaged or dirty injection nozzles - Replace injection nozzles.
Faulty fuel injection pump - Install a new pump or rebuild.
Incorrect valve timing - Correct or replace timing gear.
Fuel pipes clogging - Service fuel pipes.
Incorrect injection timing - Adjust as recommended.
Excessive wear of piston rings and cylinder - Change defective components.
| Diesel starts and stalls immediately |
Fuel filter plugged - Change the filter element.
Fuel injection pump is damaged - Repair or replace injection pump.
Dirty air filter - Clean air cleaner element.
Unadjusted nozzle opening pressure - Adjust as required.
| Engine stops suddenly during operation |
Timing of fuel injection pump is incorrect - Set it up as required.
Clogged fuel filter - Install new filter element.
Low coolant temperature - Warm up to required temperature.
Injection nozzles sticking or clogged - Clean or change injection nozzles.
Low idle speed setting is not correct - Adjustment required.
Valve out of adjustment - Check and adjust as required.
Fuel injection pump is broken - Change pump or rebuild it.
Fuel injection nozzles are damaged - Clean or change injection nozzles.
Dirty fuel hoses or lines - Service fuel lines and hoses.
Clogged air cleaner - Change air filter element.
Cylinder-head gasket is broken - Replace the gasket as required.
Injection timing is wrong - Adjust injection timing as required.
Fuel injection pump failure - Change or repair the pump.
Any of moving engine parts is worn - Repair or replace defective components.
Dirty radiator fins or faulty radiator cap - Clean radiator or replace cap.
Lack of coolant in cooling system - Add coolant fluid to cooling system and also check it for leaks.
Fan belt is broken or worn - Fan belt must be replaced.
Engine oil level is low - Fill up the engine oil.
Cylinder head gasket is defective - Change cylinder head gasket.
Injection timing is out of adjustment - Use correct injection timing adjustment.
| Oil pressure is insufficient |
Oil level is low - Fill the crankcase with oil.
Oil pump is damaged - Replace as required.
Dirty oil filter element - Change or clean engine oil filter element.
Relief valve is stuck or broken - Change or clean relief valve.
Clearance of crankshaft bearing is excessive - Inspect and replace or repair faulty components.
Crankpin bearing clearance is excessive - Check and replace or repair defective parts.
| High engine oil consumption |
Oil leaks: Defective seals or gaskets - Replace defective parts.
Improper oil viscosity - Fill up with the proper oil viscosity.
Damaged or seized piston rings - Change piston rings.
Damaged valve stems or valve guides - Install new valves.
Scored pistons or cylinder liners - Check pistons and liners, change as required.
Engine not warmed up - Engine is not warmed up to the required temperature.
Insufficient engine oil - Need to add engine oil.
Incorrect adjustment of fuel injection pump timing - Adjust according to specifications.
Piston wear or scoring - Install new pistons.
Misaligned or defective connecting rod - Connecting rod needs to be replaced or aligned.
Low battery power - Battery is drained, charge it.
Battery is not holding charge - Service or change the battery.
Battery cables are disconnected or terminals are faulty - Connect wiring correctly or install new terminals.
Battery is low or faulty - Charge or change the battery.
Disconnected or incorrectly connected wires - Inspect battery wires and connect correctly.
Low battery power - Battery is drained, recharge it.
Starter motor failure - Starter should be replaced.
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