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First Breakdown in the Porsche
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Author:  willrayden [ Mon Oct 21, 2013 8:50 am ]
Post subject:  First Breakdown in the Porsche
The 924S died on the way to work this morning, i am hoping for a little bit of internet diagnosis...

I have noticed last week that it has been taking a little longer cranking to start her up, but all running fine.

Tried to start this morning and it took ages to get her to start (by ages I mean 3 cranks of maybe 5 secs each). She was fine for a mile or so, then hesitated a little when I pulled away from stand still. Thought it was odd, but was still running fine. Another mile down the road, sat at lights for 20 seconds, went to pull away and she was spluttering and wouldn't pull away. Coughing cleared and off she went, for a whole 100 yards where she died, just lost all power. I couldn't get here started again at all (tried and tried until the battery was starting to drop).

I called the AA, 20 mins later chap arrives, puts the key in and she starts first time! He then followed me home (about 5 miles), car drove fine, with not problems / hesitation / spluttering at all.

I'm thinking possibly DME relay (might go and buy one later!), does this sound like the symptoms of a DME failure?
Author:  benjj [ Mon Oct 21, 2013 9:22 am ]
Post subject:  Re: First Breakdown in the Porsche
Could be the DME relay but sounds more like an ignition or fuelling issue to me.

How are the basics? Ignition leads, dizzy, rotor arm, coil etc.
Author:  944er [ Mon Oct 21, 2013 9:31 am ]
Post subject:  Re: First Breakdown in the Porsche
Hi there,

I had a similar thing happen to me recently. The car would only click rather than crank, every other time or so, and then would start on the third time. Then last week the car cut out on me as I had just come out from work. All lights came on and it wouldn't turn over. Eventually, AFTER I'd called the AA out, it started again and then was fine all the way home. I immediately ordered a DME relay and put the new one in - no problems since!

I think the classic symptoms are: not starting every time, cutting out and not re-starting until the DME cools down... there may be others too.

From Clark's Garage:

"Symptoms of a failing DME relay may appear in several ways. Early on, the car may not start or be difficult to start when the engine has been shut down and restart is attempted while the engine is still warm (actually while the DME relay is still warm). When this happens, the car will normally restart when it is allowed to sit and cool for a period of time (usually from 30 minutes up to 2 hours). Another possible failure mode is for the car to suddenly die while driving down the road. Again, the car will often restart after it is allowed to cool.

If your car will not start and you suspect the DME relay may be bad, try tapping on the DME relay and then attempt to restart the car. You might also have an assistant tap on the relay while you attempt to start the car. This will often temporarily fix the DME relay to get the car started.

If you experience a DME relay failure and you can not immediately get a new relay, you can get the car home by removing the relay and jumpering the relay terminals on the relay / fuse panel to supply power to the DME and fuel pump. DO NOT leave the jumpers installed when the car is not running. This will cause the DME computer to be continuously energized and the fuel pump to run continuously which will drain the battery. Jumper fabrication and installation will be covered later in this procedure."

http://www.clarks-garage.com/shop-manual/fuel-05.htm

I got one from porsche-apart on ebay - £25 and delivered the next day. I asked Porsche and it was over £60 plus VAT. Given that it will eventually fail wherever it is bought from, I reasoned it may as well be purchased from anywhere.
Author:  tr7v8 [ Mon Oct 21, 2013 9:42 am ]
Post subject:  Re: First Breakdown in the Porsche
DME relay, also what state are the ignition leads, plugs & rotor arm & cap in?
Author:  willrayden [ Mon Oct 21, 2013 9:56 am ]
Post subject:  Re: First Breakdown in the Porsche
Plugs, leads have done about 10k miles since i replace them a couple of years ago. Rotor arm / cap look ok (i checked them when i replace the injector seals a couple of weeks ago) no scorching or anything.

I've just pulled the relay and am going to make up a set of jumper leads and try that, it's hard to diagnose though as it was fine when started again (which also make me think DME).

I think i might have to get the Mini roadworthy again so I have a back-up!
Author:  AlpineTurbo [ Mon Oct 21, 2013 11:09 am ]
Post subject:  Re: First Breakdown in the Porsche
That to me sounds possibly like a DME relay or a Fuel pressure regulator. I would change the DME as a matter of course, and for the FPR I would look into disconnecting an injector lead the next time the car dies completely to see if it will run again.

What are your battery connections like? You say it took ages to start the car up?
Author:  willrayden [ Mon Oct 21, 2013 11:17 am ]
Post subject:  Re: First Breakdown in the Porsche
Battery was new in January and is still good (showing 14v on the dial)

I have ordered a new DME, just been out again and it was completely fine. I think it might have had a new fuel pressure regulator earlier this year, i need to check the receipt, but I have a felling he did the fuel lines, filter and pressure regulator (but not the pump).

All seems fine and dandy at the moment!! I'm going to put some spare wire in the car as a temp DME jumper for tomorrows commute...
Author:  broady_6 [ Mon Oct 21, 2013 1:32 pm ]
Post subject:  Re: First Breakdown in the Porsche
Nothing to do with a bad earth and the particularly wet weather weve had?
Author:  madrob6 [ Mon Oct 21, 2013 2:20 pm ]
Post subject:  Re: First Breakdown in the Porsche
Just to throw something else into the mix. There's a strainer inside the fuel tank which may benefit from a clearout, also check when the fuel filter was last changed and try measuring the fuel flow rate.

It sounds similar to mine when it had so little fuel in the tank that the pump couldn't pump enough through so potential fuel starvation.
Author:  willrayden [ Mon Oct 21, 2013 4:31 pm ]
Post subject:  Re: First Breakdown in the Porsche
I'm pretty sure it's DME now, just been out for a run until it started coughing. Pulled the DME (which was very hot) put the jumper wire in and it drove home with no problems.

However on inspecting the leads and plugs I noticed that there is a hairline crack in my fuel rail which is seeping fuel. I have temp fixed it with fuel tank sealer (it's not spraying out, so it should hold) but will need to get a new rail at some point soon... Back to Ebay!
Author:  JasonGibson [ Mon Oct 21, 2013 6:02 pm ]
Post subject:  Re: First Breakdown in the Porsche
It`s also worth pulling the fuses and cleaning the contacts on fuse and fuse holder
Author:  GlennS [ Mon Oct 21, 2013 6:17 pm ]
Post subject:  Re: First Breakdown in the Porsche
willrayden wrote:
I'm pretty sure it's DME now, just been out for a run until it started coughing. Pulled the DME (which was very hot) put the jumper wire in and it drove home with no problems.

However on inspecting the leads and plugs I noticed that there is a hairline crack in my fuel rail which is seeping fuel. I have temp fixed it with fuel tank sealer (it's not spraying out, so it should hold) but will need to get a new rail at some point soon... Back to Ebay!


That explains the fuel smell at the White Lion, then :)

My vote for your starting / running problems goes to the DME relay too.
Author:  willrayden [ Mon Oct 21, 2013 6:53 pm ]
Post subject:  Re: First Breakdown in the Porsche
just been out for a quick check, temp fix of fuel rail may have stemmed the flow a little, but I have just bought a new(ish) rail from ebay, so will have to swap this over at the weekend.

Maybe my fuel economy will go up once it's fixed!!
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