Yanmar 4TN84 Troubleshooting
| Engine Model: Yanmar 4TN84 |
| Engine Type: 4-cycle 4-cylinder direct injection liquid-cooled diesel |
| Total Displacement: 116.3 cu.in (1.91 L) |
| Rated Engine Power: 44.8 Hp (33.4 kW) at 2900 rpm |
| Aspiration Type: Naturally aspirated |
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| Engine starts hard or doesn't start |
Clogged fuel filter - Change the filter element.
Air in the fuel lines - Bleed the fuel lines.
Dirty or damaged injection nozzles - Check injection nozzles and replace if required.
Faulty fuel injection pump - Install a new pump or rebuild.
Valve timing is incorrect - Correct or replace timing gear.
Dirty fuel pipes - Clean fuel pipes.
Wrong injection timing - Set up as recommended.
Worn piston rings and cylinder - Replace defective components.
| Diesel starts but immediately stops |
Dirty fuel filter - Change the filter element.
Fuel injection pump is damaged - Replace or rebuild injection pump.
Intake air restriction - Clean or change.
Nozzle opening pressure is incorrect - Adjust as recommended.
| Engine shuts off suddenly while running |
Timing of fuel injection pump is incorrect - Adjust according to specifications.
Fuel filter element clogging - Service the filter.
Engine is not warmed up to the required temperature - Warm up the engine.
Defective or stuck injection nozzles - Change or repair injection nozzles.
Improperly adjusted low idle speed - Adjust as required.
Excessive valve clearance - Check and adjust.
Fuel injection pump malfunction - Change pump or rebuild it.
Fuel injection nozzles are damaged - Check injection nozzles and replace if required.
Fuel hoses or lines are clogged - Fuel hoses and lines must be clean.
Restricted intake air - Replace air filter element.
Leaking cylinder head gasket - Change cylinder head gasket.
Injection timing is wrong - Use correct injection timing adjustment.
Fuel injection pump failure - Install a new pump or rebuild.
Any of moving engine components is faulty - Repair or replace defective components.
Radiator core is dirty or radiator cap is damaged - Clean radiator or change cap.
Low coolant level - Add coolant fluid to cooling system and also check it for leaks.
Loose or damaged fan belt - The fan belt needs to be replaced.
Insufficient engine oil - Add oil to the engine crankcase.
Cylinder-head gasket is broken - Cylinder-head gasket replacement required.
Unadjusted injection timing - Set up as recommended.
Lack of oil - Need to add oil.
Worn oil pump - Inspect and change as required.
Dirty oil filter element - Change or service engine oil filter.
Stuck or defective relief valve - Relief valve need to be replaced or cleaned.
Clearance of crankshaft bearing is excessive - Inspect and change or repair worn components.
Excessive crankpin bearing clearance - Inspect and change or repair worn components.
| High engine oil consumption |
Oil leaking: Seals or gaskets are wearing excessively - To repair leaks, replace worn parts.
Crankcase oil too light - Fill up with the proper oil viscosity.
Damaged or seized piston rings - Replace piston rings.
Valve guides and stems are worn - Valves replacement required.
Pistons or cylinder liners are scuffed - Inspect liners and pistons, fit new parts as necessary.
Engine is cold - Warm up engine as required.
Engine oil level is low - Add oil to the engine crankcase.
Improper fuel injection timing - Adjust according to specifications.
Pistons are worn or scored - Install new pistons.
Connecting rod is defective or not aligned - Connecting rod needs to be aligned or changed.
| Starter motor cranks slow |
Low battery power - Charge the battery.
Battery will not hold charge - Battery needs service or replacement.
Bad battery terminals or disconnected wiring - Check wiring connections and replace or clean terminals.
Battery is drained or worn - Replace or charge as required.
Wire harness is disconnected or incorrectly connected - Check wire harness and connect as required.
Low battery capacity - Charge the battery.
Starter motor failing - Change or repair starter.
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