Non starter

Very recently I read a piece in your column about a car that "shut down" and simply wouldn’t start when the owner tried to move it within his drive. If I remember your reply correctly you said it was something to do with trying to start the car too quickly again after having switched it off and that in such a circumstance some part of the engine fills with petrol (or doesn’t?) and it simply will not start. I think you also spoke about it being a 'protective' feature to prevent further damage. I'm sitting here looking at my 20056/55 Jaguar S Type in my drive and that's exactly what's happened. I am waiting for Green Flag to come to me. I no longer have that earlier copy of the Daily Telegraph and I have tried looking for your reply on the website and in you FAQs as it might help a mechanic get mine sorted out but I cannot find it. Should I be able to find it please, or is it possible for you to kindly repeat it for me? I should add that I do not know anything about what makes a car work - I can only drive them.

Asked on 24 January 2009 by

Answered by Honest John
Yes, that's what happens. Start a petrol engine from cold and it immediately fills with fuel and condensation. Shut it off without getting the engine to temperature and that neat fuel and condensation remains in the engine. It is detected by the lambda sensor in the exhaust and this prevents the engine from being restarted and blasting neat fuel into the catalytic converter that could destroy the cat matrix. This has a secondary benefit of preventing the engine being started when the oil lubrication in its bores is washed off by the neat fuel. So probably nothing wrong with your car. Everything wrong with the way you have been treating it. If you just leave it alone for a few hours it may clear itself and start. Another possibility is that an engine with dirty oil does not immediately pump up its hydraulic tappets and by the time it does the engine is awash with fuel so the lambda sensor and ECU will not let it start. Older diesels are more tolerant of this treatment because diesel fuel itself has some lubricity. But modern diesels with particulate filters don't like it at all because the filter can get blocked.
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