Yanmar 3TNC78 Troubleshooting
| Engine Model: Yanmar 3TNC78 |
| Engine Type: 4-cycle 3-cylinder direct injection liquid-cooled diesel |
| Total Displacement: 69.9 cu.in (1.15 L) |
| Rated Engine Power: 27.1 Hp (20.2 kW) at 3400 rpm |
| Aspiration Type: Naturally aspirated |
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| Engine difficult to start or won't start |
Fuel filter plugging - Change filter element.
Air in fuel tank - Bleed fuel tank.
Fuel injection nozzles fault - Clean or replace injection nozzles.
Fuel injection pump malfunction - Replace or rebuild injection pump.
Valve timing is out of adjustment - Adjust or replace timing gear.
Fuel pipes are clogged - Clean or change fuel pipes.
Improper injection timing - Adjust as recommended.
Worn piston rings and cylinder - Replace faulty parts.
| Engine starts but stops suddenly |
Fuel filter element is dirty - Service or replace the filter.
Fuel injection pump is faulty - Repair or install new pump.
Intake air restriction - Replace air filter element.
Improper nozzle opening pressure - Adjust as required.
| Engine stalls during operation |
Fuel injection timing is not adjusted - Adjust the pump as required.
Dirty fuel filter - Replace filter element.
Engine is cold - Warm up the engine.
Injection nozzles are stuck or clogged - Service or change injection nozzles.
| Engine stalls when idling |
Low idle speed set incorrectly - Adjust the low idle speed.
The valve clearance is incorrect - Have it adjusted.
Defective fuel injection pump - Replace or rebuild injection pump.
Fuel injection nozzles fault - Inspect nozzles and replace if necessary.
Fuel hoses or lines are dirty - Fuel lines and hoses need to be cleaned.
Dirty air filter element - Carry out maintenance on air filter.
Blown cylinder head gasket - Change cylinder head gasket.
Wrong injection timing - Set the injection timing correctly.
Fuel injection pump is faulty - Replace or repair injection pump.
One of moving engine parts is faulty - Change or repair damaged parts.
Dirty radiator fins or defective radiator cap - Replace cap or clean radiator.
Engine coolant is insufficient - Add coolant fluid and inspect the cooling system for leaks.
Fan belt slipping or worn - Belt change is required.
Insufficient engine oil - Fill up the oil to required level.
Blown cylinder head gasket - Gasket should be replaced.
Injection timing is out of adjustment - Set up as recommended.
Lack of oil - Fill crankcase to proper oil level.
Oil pump malfunction - Install a new pump.
Dirty oil filter - Service or change engine oil filter element.
Relief valve is stuck or worn - Replace or clean relief valve.
Crankshaft bearing clearance is excessive - Check and change or repair defective parts.
Excessive oil clearance of crankpin bearing - Inspect and replace or repair faulty components.
| Engine consuming too much oil |
Oil leakage: Defective seals or gaskets - Replace to repair leaks.
Improper oil viscosity - Fill up with the proper oil viscosity.
Piston rings are stuck or worn - Piston rings need to be replaced.
Valve guides and stems are worn - Valves need to be changed.
Cylinder liners or pistons are scuffed - Check pistons and liners, change as required.
Low coolant temperature - Warm up the engine.
Engine oil insufficient - Need to add engine oil.
Fuel injection pump timing is wrong - Set the fuel pump timing correctly.
Pistons are broken or worn - Have pistons replaced.
Connecting rod is misaligned or worn - Connecting rod must be aligned or replaced.
Low battery voltage - Charge the battery.
Battery runs out quickly - Service charging system or install new battery.
Bad battery terminals or disconnected wiring - Check battery wires and service or replace terminals.
Battery is drained or worn - Need to charge or replace the battery.
Battery cables are disconnected or incorrectly connected - Check cables and connect as needed.
Low battery voltage - Battery needs to be recharged.
Defective starter motor - Repair or replace starter.
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