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| Home / Car Engines / Toyota Engines / Toyota 12H-T |
Toyota 12H-T Troubleshooting
| Diesel hard to start or doesn't start |
Fuel filter plugging - Replace filter element.
Air in the fuel lines - Bleed the fuel lines.
Dirty or damaged injection nozzles - Clean or replace injection nozzles.
Damaged fuel injection pump - Repair or change injection pump.
Valve timing is incorrect - Adjust or replace timing gear.
Fuel pipes are clogged - Clean fuel pipes.
Injection timing is wrong - Check injection timing adjustment.
Excessive wear of piston rings and cylinder - Replace defective components.
| Diesel starts but immediately shuts off |
Fuel filter plugging - Service the filter.
Fuel injection pump damage - Repair or change injection pump.
Air cleaner is dirty - Change air filter element.
Unadjusted nozzle opening pressure - Adjust as required.
| Engine stalls after running |
Improper fuel injection timing - Adjust fuel injection pump as required.
Fuel filter element clogging - Service the filter.
Engine not warmed up - Normalize the temperature by warming up the engine.
Defective or stuck injection nozzles - Clean or replace injection nozzles.
| Engine stalls while idling |
Improperly adjusted low idle speed - Adjustment required.
The valve clearance is incorrect - Adjust to proper valve clearance.
Fuel injection pump is broken - Repair or change injection pump.
| Diesel power loss |
Dirty or faulty injection nozzles - Replace injection nozzles.
Fuel lines or hoses clogging - Clean fuel hoses and lines.
Intake air restriction - Air filter maintenance required.
Leaking cylinder head gasket - Replace cylinder head gasket.
Unadjusted injection timing - Set the injection timing correctly.
Fuel injection pump is broken - Rebuild or change fuel pump.
Any of moving engine parts is worn - Change or repair damaged parts.
| Engine overheats |
Radiator core is clogged or radiator cap is leaking - Replace cap or clean radiator.
Engine coolant is insufficient - Fill the cooling system and check components for leaks or other faults.
Fan belt is broken or worn - Replace the fan belt.
Engine oil insufficient - Check oil level and add oil as required.
Blown cylinder head gasket - Install a new gasket.
Injection timing is wrong - Set the injection timing correctly.
| Low oil pressure |
Not enough oil in the engine - Fill the crankcase with oil.
Oil pump failure - Repair or change.
Oil filter is dirty - Clean or replace engine oil filter element.
Relief valve is seized or worn - Change or service relief valve.
Crankshaft bearing clearance is excessive - Test and replace or repair worn components.
Crankpin bearing clearance is excessive - Test and repair or replace worn parts.
| Engine using too much oil |
Oil leaking: Damaged gaskets or seals - New components need to be installed.
Oil viscosity is wrong - Use oil of correct viscosity.
Damaged or seized piston rings - Piston rings replacement required.
Valve stems or guides are damaged - Valves replacement required.
Scuffed pistons or cylinder liners - Inspect pistons and liners, replace as required.
| Engine knocking sound or abnormal noise |
Engine not warmed up - Normalize the temperature by warming up the engine.
Engine oil level is insufficient - Fill up the engine oil.
Improper fuel injection timing - Adjust fuel injection pump as required.
Worn or scored pistons - Replace the pistons as required.
Misaligned or faulty connecting rod - Connecting rod needs to be replaced or aligned.
| Starter motor cranks slow |
Low battery voltage - Battery needs to be recharged.
Battery is not holding charge - Service battery or change it.
Disconnected cables or faulty battery terminals - Check cable connections and change or clean terminals.
| Starter will not work |
Battery is drained or worn - Need to charge or replace the battery.
Disconnected or incorrectly connected wires - Inspect battery wires and connect correctly.
Low battery output - Recharge the battery.
Starter motor failing - Replace or repair starter.
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