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Diesel engine problems

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Solve your diesel engine problems with these easy checks!

Make Your Car Start and Run Better and Go Further


diesel engine“My car is difficult to start and it seems to have lost power!”

DIfficult starting and loss of power are among  the most common  diesel engine problems people get with their cars.


Check for:

  • Air leaks in pipes and connectors.
  • Pay close attention to air intake pipes, mass air flow meter and turbo connecting pipes.

Check for:

  • Dirty or clogged filters.
  • Diesel fuel is contaminating so regular maintenance is important. diesel engine air filter
  • Main filters to change are Fuel, Air and Oil. Fuel contains impurities so fuel filter maintenance will minimize this.
  • Change oilf filter on a regular basis to reduce engine wear to a minimum.
  • Diesel engines rely on compression to function ; clean top quality oil will keep the engine running at it’s best.

Some engines have extra filters (eg BMW diesel ) check service manual for these.

Check for:

diesel engine injector nozzle

  • Worn and/or sticking injector nozzles. Diesel injectors  give very good service overall but will eventually require replacement.
  • Common rail diesel is quiet and effeicient but is operating at very high pressure so expect to change injectors when mileage passes 100k mark (this figure will vary depending on maintenance, driving style etc. )

Check for:

  • Electrical connexions. Modern diesels are electronically controlled so electrical connexions are very important. Always check for electronic faults if you have diesel engine problems.

Check for:
Problems with the turbo.

  • Modern turbos are under pretty savage operating pressure.

Due to increasing demand for more power from smaller and smaller engines and ever  stricter emission controls turbos are spinning at high revs.

  • They are also under electronic control and this can give problems.

Diesel engine problems often involve faulty sensors or regulators.

Check for:

  • Common symptoms of sensor or regulator failure are engine cutting out regularly and unexpectedly. It will usually start OK.
    Also engine will usually run OK when under load but cut out when no throttle.

If car fails to start EOBD check is best course of action.
Diagnostics will often show fuel pressure sensor/regulator problem.

Diesel engine problems  in older cars involving difficult starting 

Check for:

  • Defective glow plugs. Indirect diesel engines are fitted with glow pluglow plug diesel enginegs for cold start. Difficult starting may be down to one or more defective glow plugs.


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(c) Andy Hewing B.Sc. February 2010