Saab Diesel Problems and Faults

 A short guide to common Saab Diesel faults.

We are often asked to diagnose vehicle problems over the phone, if only it was that simple!
Frequently we recognise a familiar problem and are able at least to narrow the fault down to on or two possible causes.
As a Saab Specialist we use the Saab Tech2 diagnostic equipment, this whilst being fantastically useful, is not the be all and end all of fault diagnosis. Computer generated fault codes only go a certain distance to point in the direction of the problem, it is rare that they specifically pin point a particular fault. Where they don’t we are left with a process of elimination based on logic, experience, and sometimes, if we’re honest a bit of luck!

The modern diesel engines are extremely sophisticated and difficult to diagnose.
One of the first areas we look at after a Tech2 scan is the state of the exhaust emissions, often there is a big clue as to the fault in the colour of any smoke emission.
Diesel smoke falls into a range of three colours, Black, White, or Blue, each will point to a particular area of the engine systems.
Below I have listed a general diagnosis of the various colours.

Black Smoke

This is generally due to air/fuel ratio imbalance. Either the fuel system is delivering too much fuel, or there is not enough air. A few things that can be at fault are:

• Faulty injectors (injectors need attention/ cleaning periodically.)
• Faulty injector pump
• Dirty air cleaner
• Turbocharger or intercooler faulty
• Problems within cylinder head, such as valves clogging owing to faulty EGR (exhaust    gas recirculation) valve
• Damaged swirl flaps in the intake manifold on the Z19DTH and DTR Saab 1.9L Diesel engine

White Smoke

This normally indicates that the fuel injected into the cylinder is not burning correctly. The smoke will be very acrid and will make your eyes sting and water.

• 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

This indicates engine is burning engine oil and can be caused by the following faults.

• 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

One other problem we are seeing more and more, especially with the increased content of Bio fuel in the mix of modern diesel in the growth of bacteria within fuel systems causing clogging and deterioration of fuel systems. I will deal with this subject in a separate post.

Prevention Tips.

 Regular use of a good quality fuel treatment will help to disperse water and contaminants in the fuel system as well as helping to keep injectors clean.

• If your diesel has a particle filter (DPF) it needs to be able to regenerate, or clean out the filter. You can ensure that this will occur if you are able to run the car at a steady 2500-3000 rpm at motorway speeds for ten minutes or so. For more information about this please read our article here
• Use a fuel additive that will enable the cars regeneration process to occur at lower temperatures. Diesel particulate matter burns when temperatures above 600 degrees Celsius are attained. This temperature can be reduced to somewhere in the range of 350 to 450 degrees Celsius by use of a fuel borne catalyst.
• Avoid the continuous use of “supermarket” diesel.
• If you suspect the filter may be blocked, a Dealer or Specialist has the computer to carry out a manual or forced regeneration

I hope that you may have found this post informative. Please feel free to contact us at Motorvation Saab by phone on 01892 825208 or visit our website at  www.motorvationsaab.co.uk