Mitsubishi 4DQ5 Troubleshooting
| Engine Model: Mitsubishi 4DQ5 |
| Engine Type: 4-cycle inline 4-cylinder naturally aspirated liquid-cooled diesel |
| Total Displacement: 127.2 cu.in (2.08 L) |
| Rated Engine Power: 50 Hp (37 kW) at 2800 rpm |
| Fuel System Type: Indirect injection |
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| Engine starts hard or will not start |
Fuel filter plugged - Service or replace the filter.
Air in the fuel pipes - Bleed the fuel pipes.
Dirty or damaged injection nozzles - Replace injection nozzles.
Fuel injection pump failure - Replacement or repair required.
Valve timing is out of adjustment - Correct or change timing gear.
Clogged fuel pipes - Clean or change fuel pipes.
Injection timing is wrong - Adjust injection timing as required.
Damaged piston rings and cylinder - Replace defective parts.
| Diesel starts and suddenly stops |
Fuel filter plugged - Change the filter element.
Defective fuel injection pump - Install a new fuel pump or repair.
Air filter is dirty - Clean or replace element.
Nozzle opening pressure is not adjusted - Set up as recommended.
| Engine stops running suddenly |
Improper fuel injection timing - Check the fuel injection pump timing adjustment.
Fuel filter plugging - Clean or change the filter.
Engine is not fully warmed up - Warm up to required temperature.
Injection nozzles are jammed or clogged - Clean or replace injection nozzles.
| Engine shuts off while idling |
Low idle speed adjustment is incorrect - Adjust the low idle speed.
Valve out of adjustment - Check and adjust.
Defective fuel injection pump - Repair or install new pump.
Fuel injection nozzles are clogged or faulty - If necessary, replace with a new nozzle.
Clogged fuel hoses or lines - Service fuel lines and hoses.
Restricted intake air - Change air filter element.
Leaking cylinder head gasket - Install new cylinder head gasket.
Injection timing is improper - Adjust injection timing as required.
Fuel injection pump failure - Change pump or rebuild it.
Any of moving engine parts is worn - Replace or repair damaged components.
Radiator core is clogged or radiator cap is leaking - Clean radiator or replace cap.
Insufficient coolant fluid - Refill to the correct level and inspect system for leaks.
Damaged or worn fan belt - Belt replacement is recommended.
Insufficient engine oil - Check oil level and add oil as required.
Defective cylinder head gasket - Cylinder-head gasket replacement required.
Wrong injection timing - Adjust injection timing as required.
Engine oil level low - Fill crankcase to proper oil level.
Oil pump failure - Install a new pump.
Engine oil filter is plugged - Service or change engine oil filter element.
Stuck or defective relief valve - Relief valve need to be replaced or cleaned.
Crankshaft bearing clearance is excessive - Check and change or repair defective parts.
Excessive oil clearance of crankpin bearing - Test and repair or replace worn parts.
| High engine oil consumption |
Oil leaking: Defective seals or gaskets - Replace worn parts to avoid leaks.
Oil viscosity is wrong - Use proper viscosity oil.
Stuck or worn piston rings - Install new piston rings.
Valve stems and guides are worn - Replace the valves.
Scored pistons or cylinder liners - Check liners and pistons, change as required.
Coolant temperature is low - Warm up the engine.
Lack of engine oil - Need to add engine oil.
Fuel injection pump timing is wrong - Adjust according to specifications.
Pistons are broken or worn - Pistons replacement required.
Connecting rod is misaligned or worn - Connecting rod needs to be replaced or aligned.
Battery voltage is low - Low battery charging, charge as required.
Battery won’t hold charge - Service battery or change it.
Disconnected cables or faulty battery terminals - Check battery wires and service or replace terminals.
Battery is drained or worn - Recharge or replace battery.
Wiring is incorrectly connected or disconnected - Inspect wiring and connect correctly.
Low battery power - Low battery charging, charge as required.
Damaged starter motor - Change or repair starter.
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