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BMW M21D24 Troubleshooting

Engine starts hard or will not start

Fuel filter plugging - Clean or replace the filter.
Air in the fuel pipes - Bleed the fuel pipes.
Fuel injection nozzles are clogged or faulty - Clean or change injection nozzles.
Fuel injection pump failure - Install a new pump or rebuild.
Valve timing is incorrect - Adjust or change timing gear.
Fuel pipes are plugged - Clean or change fuel pipes.
Wrong injection timing - Adjust according to specifications.
Piston rings and cylinder are worn - Change defective components.

Diesel starts but stalls suddenly

Fuel filter element is clogged - Service the filter.
Fuel injection pump is defective - Replacement or repair required.
Clogged air filter - Clean or change the filter.
Nozzle opening pressure is improper - Adjust as recommended.

Engine shuts off suddenly while running

Incorrect adjustment of fuel injection pump timing - Use the correct fuel injection pump timing adjustment.
Fuel filter element is clogged - Replace the filter element.
Engine has not warmed up to the recommended temperature - Engine is not warmed up to the required temperature.
Injection nozzles sticking or clogged - Change or repair injection nozzles.

Engine stalling at idle

Low idle speed set incorrectly - Adjust as required.
Valve out of adjustment - Adjust valve clearance.
Fuel injection pump is broken - Change or repair the pump.

Engine power is reduced

Fuel injection nozzles are damaged or dirty - If necessary, replace with a new nozzle.
Dirty fuel lines or hoses - Clean fuel lines and hoses.
Dirty air cleaner - Install new air filter element.
Cylinder-head gasket is broken - Cylinder-head gasket replacement required.
Incorrect injection timing - Set up as recommended.
Faulty fuel injection pump - Replace injection pump or repair it.
One of moving engine parts has broken - Replace or repair damaged components.

Engine is overheated

Defective radiator cap or clogged radiator fins - Change cap or clean radiator.
Engine coolant is insufficient - Refill to the correct level and inspect system for leaks.
Fan belt is loose or defective - Replace as required.
Insufficient engine oil - Fill up the oil to required level.
Damaged cylinder-head gasket - Replace cylinder head gasket.
Unadjusted injection timing - Adjust according to specifications.

Oil pressure is insufficient

Lack of oil - Check oil level and add oil as required.
Worn oil pump - Install a new pump.
Plugged engine oil filter - Clean or change engine oil filter.
Relief valve is seized or worn - Relief valve need to be replaced or cleaned.
Excessive crankshaft bearing clearance - Inspect and replace or repair faulty components.
Crankpin bearing clearance is excessive - Inspect and replace or repair faulty parts.

Engine consuming too much oil

Oil leakage: Seals or gaskets are wearing excessively - To repair leaks, replace worn parts.
Oil viscosity is incorrect - Use oil of correct viscosity.
Stuck or defective piston rings - Piston rings replacement required.
Damaged valve stems or valve guides - Need to replace the valves.
Pistons or cylinder liners are scored - Inspect liners and pistons, fit new parts as necessary.

Engine noises or knocks

Low coolant temperature - Engine is not warmed up to the required temperature.
Engine oil level is insufficient - Need to add engine oil.
Fuel injection pump timing is wrong - Adjust the pump as required.
Piston wear or scoring - Pistons need to be replaced.
Connecting rod failure or misalignment - Need to change or align the connecting rod.

Starter turns slowly

Battery power is low - Charge the battery.
Battery runs out quickly - Service or change the battery.
Bad terminals or disconnected battery cables - Check cables and service or change terminals.

Starter motor won't turn

Battery is low or faulty - Recharge or replace battery.
Battery cables are disconnected or improperly connected - Inspect cables and connect properly.
Low battery output - Battery is drained, charge it.
Starter motor failing - Replace or repair starter.