[Stilly50]

My 968 has an intermitant starting problem. On three occasions it has refused to start the when left over night started first thing on the morning. It cranks over fine but won't fire. Auto electricans have checked the Immobilisers and not found a problem.



The last time that it refused to start I was convinced that it was the DME relay so I replaced that. When that didn't work I figured that it could be faulty so I got another one from another source. It still cranked but wouldn't fire. I replaced the battery as I had killed the old one by this time. This was over a period of 6 weeks. I got it to fire once and it ran poorly ( 1500 revs with half throttle for 30 seconds), but wouldn't fire again.

I then trucked it to my mechanic. He is not a Porsche mechanic, the nearest Porsche mechanic is 440K away. He tested the spark, which was fine. Then it fired up strait away. He could not get it to fail again. He tested the fuel pump output, 372 kpa at idle. 2.7Liter per minute flow rate. He load tested pump and checked for aeration, both OK. Checked electrical output of pump for spikes, on faults evident.

Prior to send my 968 to the mechanic.

I have been driving it today. 3 Starts no problem.



Has anybody has a similar problem, or any ideas of what the solution may be.



StillY50

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[flash]

fuel line check valve in the rear by the pump.

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[fleetwood]

I've been having the same problem with more frequency lately, as well.

In the past, it happened every now and then -- removing the DME relay, giving it a tap, and then plugging it back in worked most of the time.

Other times, swapping in a spare relay from the glove box did the trick.



Now it's happening a lot more often, and swapping relays isnt always working.



I have a new FPR, fuel pump w/ new check valve, and fuel filter at home -- just need to get the time to install them.

My fuel pump has always been loud as long as I've had the car -- a constant droning sound.



I'll report back on how things go once I swap in the new parts.

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[rl968]

Not really sure, but a couple of thoughts.



1. Since you said it happens when car is not driven, does the battery have enough charge? Maybe you have a drain somewhere. Check the voltage before you start it.

2. Bad starter. These are known to go bad after 20 years.

3. Ignition coil

4. Bad injectors



Others hopefully will chime in to debunk my thoughts.

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[DaveN]

Definitely sound like starvation in there somewhere.

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[968TDG]

I recently had really poor starts especially after leaving the car for more than a few days. Replacing the check valve and the fuel filter fixed the issue, and made the car run smoothly.

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[Stilly50]

Thanks Guys for your suggestions. More investigations over the weekend Tended to suggest that it was a fuel starvation problem. We are going to check out the immobiliser. We felt that it may be reconnecting the ignition but sometimes not the fuel pump.



Stitty50

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[AJG]

Taking out the DME relay and hardwiring some of the pins on it will let the pump run to check if it is causing a problem. I think Clark's garage shows the pins to hardwire. This is not a permanent solution as the pump will run even when the ignition is off I think. Just use this idea sparingly!

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[Stilly50]

We have bypassed the fuel pump from the immobiliser because the immobiliser seems to be the only thing left to test. We have tested it before but as the fault is imtermitant it never faults when an auto electrician is around. It's working fine now but only time will tell.

Stilly50

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[flash]

immobiliser???

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[ds968]

i recall someone else talking about the immobiliser in their 968, but not sure they were referring to an aftermarket security system they put in

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[tamathumper]

I thought it's what the Brits call the alarm system.

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[Inkedupfatboy]

Yea, I was wondering about that too...

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[Stilly50]

In Western Australia all cars sold must have an anti theft devise fitted that is self arming. They disconnect the fuel pump, the starter motor and the Ignition. On new cars they are factory fitted. I purchased this car from Sydney where they don't have this silly law, so I had to have it fitted before it could be licenced. On Thursday we bypassed the immobiliser for the fuel pump. The car started perfectly until Saturday afternoon. I stalled the car at My front gate, and it wouldn't start. Luckily I only had 70meters to push it. It has been suggested that there could be a pinched wire where the wire goes through the floor of the boot to the fuel pump. I'm going to check it out tonight.



Stilly50

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[Inkedupfatboy]

Australia has some funky laws. Not to mention their stance on gun control. Horrible. A beautiful place but I am glad I don't live there.

Good luck on fixing your car.

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[flash]

this sure sounds like either the DME relay or the check valve

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[fleetwood]

[quote name='fleetwood' timestamp='1378481306' post='148795']

I've been having the same problem with more frequency lately, as well.

In the past, it happened every now and then -- removing the DME relay, giving it a tap, and then plugging it back in worked most of the time.

Other times, swapping in a spare relay from the glove box did the trick.



Now it's happening a lot more often, and swapping relays isnt always working.



I have a new FPR, fuel pump w/ new check valve, and fuel filter at home -- just need to get the time to install them.

My fuel pump has always been loud as long as I've had the car -- a constant droning sound.



I'll report back on how things go once I swap in the new parts.

[/quote]



finally replaced the FPR, fuel pump and both fuel filters (inside the tank prior to fuel pump and the exterior one after the fuel pump) -- runs a Lot smoother, and the fuel pump is Quiet (previous one had always made a loud constant droning noise).



prior to replacing all of that, I cleaned up a corroded ground wire on the right side of the engine bay near the windshield washer fill --- i dont know if it was a coincidence or not, but my starting problems dropped drastically in frequency after doing so (had been up to 2-3 times a week pulling or swapping dme relays to start -- yesterday was the first time I had to do that since).

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[Jono]

I just experienced a similar problem last weekend, I drove my car out of the garage for a clean and when I went to reverse back in a few hours later it just refused to fire. Fortunately it was just a few metres to push it back into the garage with some teenage help.



The starter motor is virtually brand new and turns the engine over no problem, but it refuses to fire. I've never had a starting problem in the past except for when the battery gets old and when the starter motor needed reconditioning. Our 968 is of UK origin and has the 'factory' immobiliser installed although I think it was actually installed by the UK Porsche dealers rather than in Germany. Except for the ignition I don't know what else the immobilser disconnects (if anything) however given that I can turn the car over I have to think the immobiliser is okay. I have a spare DME relay I bought a few years ago so might give that a go in the first instance and report back.



On a side note our 968 also has the standard alarm system as well as the immobiliser. The immobiliser self-arms about 20 secs after the ignitiion key is removed however I don't believe it arms the alarm which occurs when the car is locked (I stand to be corrected! - I haven't tested the theory).

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[flash]

weird. there is no immobiliser on the US versions

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[DaveN]

Nor in the CDN version, just the straight alarm.

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