Yanmar 3TNE78A Troubleshooting
| Engine Model: Yanmar 3TNE78A |
| Engine Type: 4-cycle 3-cylinder direct injection liquid-cooled diesel |
| Total Displacement: 73.4 cu.in (1.20 L) |
| Rated Engine Power: 31.1 Hp (23.2 kW) at 3600 rpm |
| Aspiration Type: Naturally aspirated |
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| Engine hard to start or won't start |
Dirty fuel filter - Clean or change the filter.
Air in fuel system - Bleed fuel system.
Defective or clogged injection nozzle - Clean or change injection nozzles.
Fuel injection pump is damaged - Change pump or rebuild it.
Valve timing is out of adjustment - Correct or replace timing gear.
Dirty fuel pipes - Clean fuel pipes.
Injection timing is incorrect - Set up as recommended.
Piston rings and cylinder are worn - Replace faulty parts.
| Diesel starts and stalls immediately |
Dirty fuel filter - Replace filter element.
Fuel injection pump failure - Replace injection pump or repair it.
Intake air restriction - Change air filter element.
Nozzle opening pressure is not adjusted - Adjust according to specifications.
| Engine shuts off suddenly during operation |
Fuel injection timing is wrong - Adjust fuel injection pump as required.
Fuel filter plugged - Change filter element.
Engine is not warmed up to the required temperature - Warm up to required temperature.
Injection nozzles sticking or clogged - Repair or replace injection nozzles.
| Engine stalls at low idle speed |
Improperly adjusted low idle speed - Normalize low idle speed.
Valve clearance is out of adjustment - Check and adjust.
Fuel injection pump is not operating properly - Repair or install a new fuel pump.
Defective or clogged injection nozzle - Test injection nozzles and change if necessary.
Dirty fuel lines or hoses - Clean fuel lines and hoses.
Air cleaner is dirty - Clean or replace the element.
Leaking cylinder head gasket - Cylinder-head gasket replacement required.
Injection timing is incorrect - Check injection timing adjustment.
Fuel injection pump failure - Install a new pump or rebuild.
One of moving engine components is worn - Replace or repair damaged components.
Clogged radiator core or damaged radiator cap - Replace cap or clean radiator.
Lack of engine coolant - Fill the cooling system and check components for leaks or other faults.
Excessive wear of the fan belt - Belt change is required.
Engine oil level is insufficient - Fill up the engine oil.
Leaking cylinder head gasket - Install new cylinder head gasket.
Injection timing is out of adjustment - Set the injection timing correctly.
Engine oil insufficient - Fill up the engine oil.
Oil pump malfunction - Replace as required.
Clogged oil filter - Service or replace engine oil filter.
Relief valve is defective or dirty - Replace or clean relief valve.
Crankshaft bearing clearance is excessive - Test and repair or replace worn parts.
Excessive crankpin bearing clearance - Inspect and replace or repair faulty components.
| Excessive engine oil consumption |
Oil leaking: Gaskets or seals may be damaged - New components need to be installed.
Improper oil viscosity - Fill up with the correct oil viscosity.
Worn or stuck piston rings - Replace piston rings.
Valve guides and stems are worn - Replace defective valves.
Scored pistons or cylinder liners - Check liners and pistons, replace as required.
| Engine knocking sound or abnormal noise |
Engine is not preheated - Normalize the temperature by warming up the engine.
Engine oil level is low - Check oil level and add oil as required.
Timing of fuel injection pump is incorrect - Adjust fuel injection pump as required.
Pistons are scored or worn - Pistons need to be replaced.
Connecting rod misalignment or failure - Alignment procedure or replacement is required.
Battery power is low - Charge the battery.
Battery will not hold charge - Service charging system or install new battery.
Bad battery terminals or disconnected wiring - Connect cables properly or replace terminals.
Battery is low or faulty - Battery needs to be recharged or replaced.
Disconnected or improperly connected wiring harness - Inspect battery wiring harness and connect as required.
Low battery output - Low battery charging, charge as required.
Starter motor failing - Repair or change starter.
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