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Kubota D640 Troubleshooting

Engine Model: Kubota D640
Engine Type: 4-cycle 3-cylinder liquid-cooled diesel engine
Total Displacement: 38.9 (0.64 L)
Rated Engine Power: 16.0 Hp (11.8 kW) at 3200 rpm
Aspiration Type: Naturally aspirated


Engine starts hard or won't start

Fuel filter element is clogged - Change filter element.
Air trapped in fuel system - Bleed air.
Dirty or damaged injection nozzles - Check injection nozzles and replace if required.
Fuel injection pump malfunction - Install a new pump or rebuild.

Diesel starts and suddenly stops

Fuel filter element clogging - Filter maintenance required.
Fuel injection pump is not operating properly - Replace or repair injection pump.
Air cleaner is dirty - Replace air filter element.

Engine stalls while running

Improper setting of fuel injection pump timing - Adjust as recommended.
Fuel filter plugged - Clean the filter element.
Engine is not warmed up to the required temperature - Engine is not warmed up to the required temperature.

Engine stalls while idle

Incorrect low idle setting - Test and adjust.
The valve clearance is not adjusted - Adjust valve clearance.
Fuel injection pump is damaged - Repair or install new pump.

Engine loses power

Clogged or defective injection nozzles - Service or change injection nozzles.
Restricted fuel lines or hoses - Fuel lines and hoses need to be cleaned.
Clogged air filter element - Clean or change.
Damaged cylinder-head gasket - Replace the gasket as required.

Engine is overheated

Radiator fins are dirty or radiator cap is defective - Clean radiator or change cap.
Lack of coolant in cooling system - Add coolant and check the components of cooling system.
Damaged or worn fan belt - Change as required.
Not enough engine oil - Check and refill engine oil.

Insufficient oil pressure

Not enough oil in the engine - Add oil as required.
Defective oil pump - Repair or replace.
Plugged engine oil filter - Change or service engine oil filter.

Diesel engine using too much oil

Oil leaking: Worn seals or gaskets - New components need to be installed.
Oil viscosity is wrong - Use correct viscosity oil.
Piston rings are seized or worn - Piston rings replacement required.
Valve guides or stems are damaged - Valves need to be changed.
Worn pistons or cylinder liners - Check liners and pistons, replace as required.

Engine knocking or noise

Low coolant temperature - Engine is not warmed up to the required temperature.
Insufficient engine oil - Checking oil level and add if necessary.
Fuel injection pump timing is wrong - Adjust the pump as required.
Pistons are worn or scored - Replace the pistons.
Connecting rod is defective or misaligned - Align or change connecting rod.

Starter turns slow

Battery capacity is low - Battery is drained, recharge it.
Battery will not hold charge - Service battery or replace it.
Bad terminals or disconnected battery cables - Check cables and clean or change terminals.

Starter will not crank

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 - Recharge the battery.
Starter motor is faulty - Repair or change starter.