Diesel Engine Issues – The Answers May Be In The Exhaust Smoke

Diesel Engine Issues - The Answers May Be In The Exhaust Smoke
Diesel Engine Issues - The Answers May Be In The Exhaust Smoke

Diesel engine issues, are frustrating and can be costly to repair.

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

Consequently, Finding and solving diesel engine issues, could be in the color of the exhaust smoke.

So, diesel engine issues, may keep you up at night, but, they don’t have to.

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.

Diesel Engine Issues - The Answers May Be In The Exhaust Smoke
Diesel Engine Issues – The Answers May Be In The Exhaust Smoke

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 pinpoint the problem. But, they do bring up an array of codes, that could be either this or that.

So, You Are Having Diesel Engine Issues.  And, You Take Your Vehicle To Your Local Mechanic. What Do You Think, When They Tell You:

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

Common rail diesels are the new hi-tech breed of diesel, to meet ever increasing emission standards. Operating pressures and temperatures are, several times higher than older technology. Also, tolerances are much finer, making them more susceptible to, fuel and carbon deposit issues. Injectors and pumps are naturally more expensive, but problems can, and do, melt pistons and destroy engines.

To start with, today’s diesel engines are extremely sophisticated and difficult to diagnose. I hope that the information below helps. It may be just confusing you, but at least it is something to start with.

Diesel Engine Issues - The Answers May Be In The Exhaust Smoke
Diesel Engine Issues – The Answers May Be In The Exhaust Smoke

So, I will give you the short version only. As a result, we will just list the most common areas to look at.

Here is the troubleshooting list, that might help or just might even 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 injectors
  • 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

We can generally understand some of the diesel engine issues, by the color of smoke, emitted from the exhaust. As a result, diagnosing the smoke may be, the window into your engine.

Consequently, There Are Three Basic Color’s, Black, White And Blue.

Black Smoke

Black Smoke
Black Smoke

Consequently, this is due to a air to fuel ratio imbalance. So, 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 include:

  • 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

White Smoke
White Smoke

Consequently, this means that the fuel injected into the cylinder, is not burning correctly:

  • 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

Blue Smoke
Blue Smoke

Consequently, the engine is most likely, 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.


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

Thank You !