Engine quit
 

I drove my 1986 911 600 miles in one day at a pretty fast speed last week, not a single problem. Once at my destination I was driving around and my engine just quit cold turkey. It failed to restart inmidiately, I waited 10 minutes and it fired right up, it did it 3 more times before the day was over. The next day I start my trip back and before the first 100 miles it quit twice, same thing, the next 500 miles averaging 80 mph not a problem. Any ideas, fuel pump, fuel filter? Thanks

First (and easiest) place to start is the DME relay. It's under the driver's seat and is easy to replace. The general rule of thumb is that the question isn't "if" the DME relay is going to fail...rather, the question is "when?" It sounds like if yours is bad, it's an intermittent problem. I replaced mine before it failed, and keep the old one in the glove box as an emergency spare.

Our host sells them for $30.50. Part number 911-618-154-00-M252.

Good luck!

Are DME relays known for intermittent failure? Could be a loose wire to one of the flywheel sensors, too.

I had the identical symptoms with my 1988 3.2 liter car. (And I mean identical. I could have written your post.)

Turned out to be a defective temperature sensor. This was replaced for about $100.- (Porsche part # 930 606 915 00) - and I never had the problem again.

Man, this is getting confusing. The entire time it was cool weather, temperature gauge was a little below the first mark. Actually when it failed was late afternoon and early morning, it was cool and damp. On the way back the day got hotter, I ended up running the AC the last 300 miles. Is there anyway to test a relay?

Sure... but it is hard to find an intermittent failure.


http://www.911chips.com/dmerelay.html

What color is your coupe? If I see you on the side of the road dead I'll stop and help.

I replied to your other post in off-topic but I might as well copy it here.
I second the DME relay. Even if you get one and it isn't that I assure you that you will want one to carry around in the glovebox. The DME realy has this habit of quitting at the most inappropriate time and it's so convenient if you can just swap it out.
That said it could well be something entirely different but most intermittent or sudden failures like that seem to be DME relays.

If you're thinking that the gauge would be reading wrong if the temperature sensor was at fault then you are not entirely correct. The gauge on your dash is showing you oil temperature. This gauge relies on a signal from the oil temperature sensor. There is another temperature sensor which measures cylinder head temperature and this provides a signal to the engine management. The engine management computer uses this information to control important stuff like fueling. If the sensor is providing useless information then the engine management starts to alter the fueling to what it is being told is happening and you could end up with all sorts of nasty things going on. You may get lucky and it's only a rough idle, or it could misfire, or just die completely.
This is the temperature sensor Dottore was talking about, NOT the one for the gauge.
Sorry if you knew this already, but I by reading your post I didn't think you did.

+1 with Aerkuld and the others. it could be several things that "could" cause the type of problem that you describe:
CHT Sensor
DME Relay
DME Control Unit
Reference Sensors
Fuel Relay/Pump/Filter
Crap in fuel tank clogging filter
Somewhat of a broad based problem, with a possibility of one or more contributing factors. Good luck with the testing!! Tony.

I did not know this, thanks for the good advice.

I too could have written your post a month or so again. I researched this to death and got extensive lists like you have gotten above. Ultimately I swapped out the DME relay first as has been suggested and have never had a problem since. Threw the old one in the glovebox only until I got another new one to replace it. I wanted a known good spare. The relay I pulled was the original with the 1986 date stamp, but after being stuck on I-95, better to be safe than sorry.

My DME relay was nice enough to warn me a few times before it was replaced. It was the original relay. For the cost just replace it and buy a spare for the glove box. If it is not the problem right now it will be a problem in the future if you still have the original relay.

Pipo - please let us know if you fixed this and what it took. I tried to PM you but it appears that you aren't set up to receive them.

I ordered the relay from the host. However, the car starts and run so I will not know for sure if that was the problem.

You shoud compare notes in a couple of weeks with

http://forums.pelicanparts.com/porsche-911-technical-forum/408534-1988-911-stops-dead.html

this one got fixed
http://forums.pelicanparts.com/porsche-911-technical-forum/358412-1987-targa-no-spark.html

and this from SW
http://forums.pelicanparts.com/porsche-911-technical-forum/391126-carrera-stalling-problem-can-you-spot-problem.html

Thanks for the reference, boy I have a lot to learhn about this car, VW were so easy...:)

I pulled my DME relay and it, too, was the original ('89) relay. Of course, I changed it out just due to age (alone),...car was completely asymptomatic....

Damned right "safe than sorry" !!!!!!!!!!!!!! Have another brand new one in the glovebox, keeping the original in the bonnet stock.

Best,

I replaced the DME relay and the temperature sensor. The car ran for a while and now is quitting again. This time start with difficulty the reps goes up and down until it shuts off.