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brokenporker

Intermittent Issue - Cranks but Won't Start...

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If you are anywhere near me (Maidenhead, Berks) I would be happy to plug in my PIWIS tester for you.

Edited by Richard Hamilton

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Things are pointing to the fuel pump being faulty - from speaking to my other half, the recovery guy checked something in the engine bay (fuel rail pressure I think) and suggested it was out of fuel (so I guess no/low fuel pressure) - at the time the low fuel warning light was on, however the trip computer said 30ish miles remaining. He added some fuel, then it started and ran. After refitting the access hatch, putting the interior back in etc it started again, so they thought it was fixed. The paperwork was filled in, tried to restart it again and it wouldn't go - at this point it was trailered home. So it looks like when it's not starting there's no fuel pressure..

Richard - we are actually pretty local - we live in Oxford, but I work in Marlow. If possible it would be great to plug it in and see what shows up...

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Things are pointing to the fuel pump being faulty - from speaking to my other half, the recovery guy checked something in the engine bay (fuel rail pressure I think) and suggested it was out of fuel (so I guess no/low fuel pressure) - at the time the low fuel warning light was on, however the trip computer said 30ish miles remaining. He added some fuel, then it started and ran. After refitting the access hatch, putting the interior back in etc it started again, so they thought it was fixed. The paperwork was filled in, tried to restart it again and it wouldn't go - at this point it was trailered home. So it looks like when it's not starting there's no fuel pressure..

Richard - we are actually pretty local - we live in Oxford, but I work in Marlow. If possible it would be great to plug it in and see what shows up...

A word of caution about the impact of fuel level on the fuel pumps in these cars: They are cooled by the fuel that surrounds the pump, so running the car low on fuel can cause the pump to overheat and suffer a premature failure.

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Sorry to read about your problem and the attempted fixes. You may have saved me a lot of wasted effort. I have the same problem with my 2005 UK 987S and was about to make a start to fixing it today. The history with my car began with intermittent water temperature sensor failures which were coincident with an increasing reluctance to hot start, just as you described with your car. The engine would spin over but not fire up for several protracted attempts. A a short time later it would start normally. The latest incident stranded me as there was no start at all, and this time a yellow engine symbol came on during each start attempt and a message advising to take the car to the dealer. I called rescue to trailer the car home, but 30 minutes later it started normally and I got myself home.

I'm thinking, as a first step, of opening the engine compartment to examine the sensor wires and connections. I'll advise you if it makes any difference.

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Well, I learned a lot about engine access, particularly that you can get at the front of the engine (giving access to drivebelts and water temp sensor) via the cover which is on the bulkhead behind the seats. Just flip up the carpet and remove the 6 10mm bolts and 2 10mm nuts and you are in. I also opened the top engine cover for good measure.

The engine was quite dusty, so gave it a clean and 'tweaked' every sensor I could see. I also entirely removed the temp sensor, rather than just disconnecting the plug, by accident. If you pull out the green plastic retaining clip, both items come away as a unit, followed by a torrent of coolant. There is a rubber sealing ring which also gets washed down onto the lower engine cover. I cleaned everything, especially the connections within the plug, and then reassembled. The result was one 'temp sensor failure warning' within a few minutes running, but none since. I have made several journeys, both long and short, which included about a dozen hot starts. So far, the no start problem has not recurred, the engine firing up immediately each time. Whether that is just perverse good luck, or if the problem is fixed, remains to be seen as I use the car more.

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Slight update, now it's had a chance to settle down..

Richard very very kindly let me plug it into the Durametric box, which showed no faults at all... After much head scratching we figured out the only thing it could be would be something on the fuel system side, so I replaced the pump, and touch wood, it's been fine ever since.

I'm not sure if the old pump was 'weak' in some way - but sometimes although it was running it wasn't generating enough pressure to run the engine. Hence when the recovery guy checked the fuel pressure, and I checked the pump was pumping into a container, it released the pressure in the fuel system, and would start again the next time it was back together.

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Just to update my situation. The water temp sensor fail indications returned, along with the 'engine cranks but won't start' problem. I bought a new sensor from Porsche ( about £19) and fitted it in less than 15 minutes. All the warnings have now disappeared and over the past three weeks the car has started instantly, whether hot or cold, and my confidence in the car is restored.

For what its worth, when I had the no start problem there was always a very strong smell of fuel after a short period of cranking and I'm guessing that the engine management system might have been sensing a very cold engine each time and was massively overfuelling, leading to the no start situation.

This was a quick and easy fix and might be the first thing to try if you are having starting problems.

Edited by britairdog

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