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Engine stopped after 45mins of idling

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Hello all - took my PI in for an MOT yesterday. It hadn't been run for a while so, before leaving, I left it running for 20mins with a bit of choke before driving over the to garage. On arrival, parked up, switched off and about 25 mins later the mechanic started it up, drove it onto the ramp and left the engine idling (800rpm, no choke) for about 45mins (he was on his own and the reception phone was ringing all the time, so it took a bit longer than normal). The engine was idling throughout. Just as he was finishing up (engine still running), it cut out. And could not be restarted. Fuel pump was running ok, gauge temperature normal, about half a tank of fuel, and plenty of spark. After about 10-15mins of farting about and just before I was about to remove one of the injectors, I'd sort of given up and elected to phone recovery (the young lad doing the MOT looked terrified and confessed it was beyond him - where do I plug the laptop in? etc). At this point I wandered out of the back of the garage and decided to call recovery. While on the phone to them, the mechanic had managed to start it and drove it around to me. Left it running, finished all the paperwork and drove 20 or so miles pretty hard before bringing it home. All seems well and I couldn't fault it. It's never done this before - I've had it for 8 years and have had many situations of being stuck in slow moving traffic on a very hot day without any problems at all (the only difference being able to rev the engine from time to time and using the additional manually-switched cooling fan in the engine bay).

Could this be my first experience of fuel cavitation?

(I'm afraid I don't know: how hot the fuel pump was or whether there's any blockage in the tank or return feed). It did pass its MOT which was nice.

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It does sound like fuel vaporisation. Do you have braided injector leads?

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Possibly old fuel, maybe sediment from the tank in the fuel lines if it has been stood for some time. Change the fuel filter if it has one and put some fresh fuel in it. This worked when my wife's Fiesta did something similar. Combination of old (thicker) fuel and old blocked fuel filter.

Keith

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I am afraid it's an old car and I am not sure I would  even have left a car idlying in the seventies for that long.  With no air being driven into the engine compartment it would get pretty hot in there and cause as keith said fuel vaporation or maybe dirty plugs. Modern cars automactically adjust the idle and we no longer have to blip the throttle like  we had to in the old days.  Also the PI runs rich at idle.  Glad you got back home Ok and did  it pass the MOT.

Roger

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Nothing a good italian tuneup won’t fix !

 

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Hi, do you have electronic ignition fitted. I had a similar situation whilst sitting in traffic.

Found the electronic ignition to be faulty. Went back to points, seems ok now.

Regards John

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I would go for electrics starting with the coil.  Change only one thing at a time.

 

Roger

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Thanks all...just to answer some of your questions...The injector leads are not braided - they look like originals....The fuel was quite new - less than a couple of months old...Standard points fitted (not electronic)....Coil seemed good - getting a good spark when turning the engine over. It seemed fuel related - one thing I omitted....the young mechanic (bless him) suggested the plugs looked a little dry when we took a couple out. I didn't have any reference to make any real judgement on it. I wasn't aware PIs run rich at idle - but this seems logical. My theory is - temperature in the garage was warm(ish), idling engine running rich, temp of fuel rising (it had been running for over an hour-and-a-half if you add up the idle time before leaving, run to the garage and idling during MOT), rising fuel temp causes it to vapourize, fuel pressure drops, PI continues to demand rich mixture at idle - and just gets starved. The 10-15 minute refusal to start caused by the time it took for the fuel temp to fall and vapourization to cease so the the pump could do its thing.

It did pass the MOT in the end!

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If you think it's fuel vaporization , check you fuel tank venting, then the pump suction system . I was running around a month  or so  ago on days of up to 40 degrees C with no apparent  vaporization, so I don't think it's an unsolvable problem.

Maybe petrol formulation. Would your winter petrol be formulated with a much higher vapour pressure than summer to aid cold starting?

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Could be the plugs getting a bit sooted up at idle, but the engine may not have restarted at all after, as a matter of interest what is the colour of the plugs like?

John

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