Diesel engine issues FAQ

Diesel engine issues are frustrating and can be costly.

Computer generated fault codes only go a certain distance to point in the direction of the problem.

Diesel Engine Issues
Diesel Engine Issues

Many Dealers, specialists and garages equipped with expensive and sophisticated diagnostic equipment still seem to struggle.

After that, it is a process of elimination, unfortunately at your expense.

The innovation of the computer generated fault diagnosis has led to a generation of mechanics that have often lost sight of the basic operating principles of the diesel engine.

Unfortunately the fault codes don’t always pin point the problem.

They do bring up an array of codes that could be either this or that.

What do you think when you hear:

  • We have tried this and it has not helped
  • Sorry there are no fault codes so we can’t find anything wrong

To start with today’s diesel engines are extremely sophisticated and difficult to diagnose.  I hope that the information below helps and does not just confuse you but at least it is something to start with and has not cost you anything.

So I will give you the short version only. Since each troubleshooting topic could have its own blog. As a result we will just list the most common areas to look at.

Diesel Engine Issues
Diesel Engine Issues

So here is the troubleshooting list that might help or just confuse you more:

  • Low compression
  • Low fuel pressure
  • Slow cranking speed
  • Glow plugs or relay faulty
  • Insufficient fuel supply
  • Fuel quality – contamination
  • Air – Vacuum in fuel supply and Blocked fuel supply
  • Faulty injector/s
  • Bad high pressure pump
  • Faulty pressure regulator – sensor
  • Bad low pressure pump
  • Air intake restriction
  • Turbo problems
  • EGR problems
  • Injector blow–by, seat leaking
  • Cam – crank sensor
  • Injector wiring harness
  • Internal engine problems

Just like our earlier post about, Spark plugs are the “window” into your engine (your only eyewitness to the combustion chamber), and can be used as a valuable diagnostic tool.

In conclusion for Diesel Engine Issues, The Answer could be in the Smoke.

We can generally understand some of the diesel engine issues by the colour of smoke emitted from the exhaust. Consequently there are three basic colours – black, white and blue.

Black Smoke

This is due to a air to fuel ratio imbalance, either the fuel system is delivering too much fuel into the engine or there is not enough clean air (oxygen ) a few things to look for :

  • Problems within injectors, plugged or wrong spray pattern due to (injectors need attention at about 100.000 to 120 000 miles)
  • Faulty injector pump
  • Dirty air cleaner
  • Turbocharger or intercooler faulty
  • Problems within cylinder head, valves clogged up due to faulty EGR (exhaust gas recycling unit)

White Smoke

As a result this means that the fuel injected into the cylinder is not burning correctly. As a result the smoke will burn your eyes.

  • Engine/pump timing out
  • Fuel starvation to the pump causing the pumps timing not to operate correctly
  • Low engine compression
  • Water/petrol in the fuel

Blue Smoke

Therefore the engine is burning engine oil

  • Worn cylinders or piston rings
  • Faulty valves or valve stem seals
  • Engine over full with engine oil
  • Faulty injector pump/lift pump allowing engine oil to be mixed with the diesel

In conclusion if you’re in doubt about whether or not your motor is in trouble, don’t hesitate to get it checked out. Because little problems can grow into big problems.

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