Porsche Enthusiasts Club Forum

I have done a 3 wire check on the dme relay and also a two wire check on the fuel pump and dme seperately but it still only runs for 20 seconds or so, does anyone have any other ideas or know of a company I could ring to ask who are friendly and dont mind giving advice. The only thing I have done since driving it back from Wales is too jack it up and paint the wheels and I have checked to make sure I havnt squashed anything and I had to replace the carpet by the bonnet release after this it now has a sticky starter and it gave a flat battery symptom but then decided too start and the battery was fine but it still wont run for more than 20 secs. I read about some kind of alarm and jumping wires etc but cant see it been that but any ideas would help I just want to drive my new toy its all ready to go to the mot station if only I could drive it there, getting very peed off now with this Porsche ownership.

You've got to be methodical!

Is there fuel pressure when it stops? Is there a spark? The minute it stops get under the bonnet see if you have a spark.
Connect a lamp on long leads across the fuel pump & see if it stays alight?

Fundamentally you need to find why it stops!

Hang in there Frog. It's only somthing simple. Post your results in blow by blow fashion & Jim can help you properly.

Cheers, I`m on nights so its going to be the weekend now before I get a chance to go over it.

Yeh it's rubbish, you'd better give it to one of us, ha ha.

The only fault I have had with my car was a dirty plug on the MAF. If this isn't working then the car won't start, or when it did it only ran until the next movement of the plug made it cut out again. My mechanic originally thought it was the fuel pump and put a new one on - but it wasn't.

right had a good go today I have found if I start the car and let it tick over it will run for 15 seconds or so but if I start it and rev it it will die a lot quicker, the higher its reved the shorter the time it will run but as soon as it stops it fires straight back up, gets me too thinking its a fuel problem where or what I`m not sure yet. Its as though the pump pressurises the fuel to start then stops pumping. I have done a pump check on the dme relay and you can hear it spark up, whirring and when the car stops its still whirring so any ideas folks....

OK, disconnect the fuel pump live lead & run a 12v lead directly to it. Hint I've used a feed from the heated rear window live in the past, this eanbles you to turn the pump on & off via the HRW switch.
From memory a feed from the ECU keeps the pump live when running.I think this is triggered from either the AFM or the coil.

okey dokey now were getting somewhere I think. I found a length of loom under the car around the fuel tank, 2 large yellow wires that have been cut with a pair of pliers, nice clean cut and in the boot under the carpet I have found the other end where it has been cut from, could these be the original fuel pump wires if so someone has obviously had the same problem and fixed in the own. I`m going to have a hunt inside the car tomorrow to see if theres a switch or something I have knocked whilst cleaning it if not i`ll put in my own switch and supply if I can find the pump anyone know, It looks like it could be above the tank I hope not as it looks a sod to get too.

Good I told you methodical works! It is quite a common bit of an immobilser circuit, so could very well have had one in the past.

As I recall the pump runs for a bit when you turn the ignition on, then shuts off until the crank trigger starts to tell it the engine is turning. So, given that you have a spark to run the fuel the pump has pressured into the system it isn't the trigger so it must be the continuing pump drive. You're on the right track in other words!

I have no idea about the yellow wires though but it sounds like someone has been in there with fists of pig-meat which is only going to make your diagnosis harder unfortunately.

Right I have put a direct feed from the battery to the pump and its whiring nicely but still cuts out and the pump is still running when it stops so I delved under the bonnet and found that the coil feed had been cut and an alarm put in so I traced the wires back to the multi plug where the alarm used to be, a mess, so I put a direct feed onto the coil live and again no change, running out of ideas now but keeping in there if the worst comes I think its going to have to go the garage and let them rewire it or what ever it needs.

Has the fuel filter been changed recently?

doubt it but I have taken the feed off the fuel rail and its flying out of there

OK check when it cuts whether you have any spark. It maybe sparks, but unusual to have it cut so quick, they normally do it once warm.