White smoke is unburned diesel

"Answer
Hi , Sorry for the delay in answering your question.
Scenario 1 ) If your engine cuts out dead as if the ignition has been turned off, whilst travelling, I would suggest a faulty fuel cut off valve or associated power supply to the solenoid. Also some of these vehicles had an anti-theft module on the fuel pump (Lucas CAV fuel system) these were very tempremental and also very difficult to diagnose as faulty if the fault was intermittant.
Scenario 2) If your vehicle cuts out gradually i.e. gradual loss of power , there have been instances where the fuel tank vent valve assembly has become blocked(located under drivers rear wheel arch ( if fitted ) thus causing a vacuum in the tank which in turn will try to draw fuel back rather than allow it to be drawn out to the fuel pump. The easy test for this if it was a Lucas system was to observe the hand primer on the top of the filter assembly. This would be drawn downwards by the vacuum. Unfortunately on a Bosch system there is no hand primerwhich again makes diagnosis difficult especially when the fault is only occuring 4 times a week.
If the vehicle was in my workshops here is what I would do.
If the system is Lucas or bosch remove the fuel cut off valve (24mm) if it is accessible as somtimes the anti-theft shields cover the solenoid. Remove the plunger and very small spring . Replace the solenoid body in the hole and use vehicle but stalling will be required to stop it. If the symptoms do not return then perhaps you will be on the right path. If they did return i would then basically remove the vent valve and leave the pipes loose and try again.
If the system is Lucas then also the hand primers do go faulty . it is a rubber diaphragm that can perish and allow air into the system that will cause cutting out and poor starting. This can be replaced for around £30 for complete top, or about £5 for a diaphragm and do it yourself, available from all good fuel injection agents!
Bosch systems are harder to diagnose and if the faults were constantly causing you probs i.e. every few hours or less, then I would suggest running fuel pipes to your injector pump from a container of diesel, ( flow and return) and see how it performs then . I do not know if you will be aware that on both systems the fuel is drawn by a vane pump inside the injector pumps and basically needs all the help it needs. Bosch pumps have a steel vane pump fitted in the drive end of the pup, and Lucas have one at the injector pipe end, both are suseptable to wear at your vehicles mileage.
You do not say also if the vehicl cuts out immediately from starting or on a journey. If from starting i would try hand priming (if fitted) the system first , as fuel can run back to the tank.
These are just a few of the many more things that could be a problem . Glow plugs are purly cold start aid and bear no significance in warm starting. Hope I have not fried your brain to much. Incidentally i am not working in the fuel injection business now , I was made redundant last Xmas. But I am now service manager in Toyota franchise , and they do not break down very often , great !
Keep in touch if the need be , I am still happy to assist .
Anthony "


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