930 stalling

zcoker · 03-29-2009, 12:58 PM

Hey guys,

Been chasing a weird problem on my 81 euro. Car starts and runs fine but when I get a certain distance from home, it just dies, usually at the same friggin location on the road! Go figure. Anyhow, I let it sit for a couple of minutes and then it starts right up and may die again. I have to let it sit before I attempt to start it because it just spins and spins - with pumps running fine. After its spell, it starts and runs fine the rest of the day, all day, anywhere without a problem. My question: is there something related to the WUR that may be causing this? I don't have the yellow relay, no connection on the back of the fuel head, no distributor (twin plugged), pumps are jumped, so no relay issues there. When this happens, pumps run fine. My guess is WUR related because it is a warm-up issue, apparently. What do u guys think?

x98boardwell · x98boardwell's Garage

Zcoker,

From reading your post it sounds like it just dies which would mean loss of spark or fuel or electrical. If there is some hesitation with your symptoms I would then turn to the fuel head or fuel distributor.

If it does in fact just die then i would say that it must be spark or fuel related. Quick question to confirm something... when it dies and you are trying to start it are the fuel pumps on for sure? If they are then you are having a loss of spark or an electrical failure. It could even be the green distributor wire from the distributor that runs to the CDI box or even the coil.

I would check some things in this order.

1) When this happens again have a spare spark plug with you and pull one of the plug wires (most likely #4 or 5) and put in the spare plug. Have a friend crank the motor and verify spark. If no spark, then possibly coil or CDI box
2) If you have spark pull the green plug behind the fuel head (between the air meter plate and fuel dist.) so that the pumps run continuously when the key is on to verify that and see if it starts. You will have to reach behind your air cleaner from the driver side and feel that switch and lightly pull on it. Be careful that it does not fall or rest by the air pump assembly when you try to start the car as this will chew it up to pieces (if you even have the air pump). If the pumps are running and you have spark then I don't know what it could be from there.

My guess is one of these things are missing when this happens. If this happens every time then take a buddy and the proper tools and narrow it down a bit. This will be a big help in the end. I hope this helps you.

Best of luck,
Bryan

zcoker · 03-29-2009, 03:01 PM

Thanks Bryan for the reply. I do not have a distributor, I have an Electromotive crank fire. The pumps run all the time with the key on and they run when this happens. I'm usually alone, so there's no way i can test spark. When it dies, it just dies, no sputtering, no misfires, like poof, off, and at the same spot down the road....weird. I have to let it sit for a few minutes and then it fires right up and never happens again the rest of the day. It appears temperature/time related, that's why I asked about the WUR.

x98boardwell · x98boardwell's Garage

Well, that helps to know that you have an Electromotive. I would say that since it is "poof" and off, then it cannot be the WUR. I could be wrong but the WUR regulates fuel pressure, I don't think it can cut it off completely. Also, it would be more consistent than just occasionally.

I would try to verify spark somehow when this happens. There may just be a shorted out wire or something that causes the system to loose spark which would give you the same feel.

Hopefully, someone else with more experience can chime in. My thought is to verify spark. I think that has to be eliminated as a possibility.

Bryan

WERK I · WERK I's Garage

Quote:

Originally Posted by zcoker

Thanks Bryan for the reply. I do not have a distributor, I have an Electromotive crank fire. The pumps run all the time with the key on and they run when this happens. I'm usually alone, so there's no way i can test spark. When it dies, it just dies, no sputtering, no misfires, like poof, off, and at the same spot down the road....weird. I have to let it sit for a few minutes and then it fires right up and never happens again the rest of the day. It appears temperature/time related, that's why I asked about the WUR.

Sounds like the crank sensor that triggers the Electromotive. I had one that would run about 20 minutes and then die every time. Wait an hour and it would start back up and then die about 10 minutes later. You probably have the small sensor would is notorious for failing.

Speedy Squirrel · Speedy Squirrel's Garage

The crank sensor gets my vote too. There is a small integrated circuit inside the sensor body. If it gets too hot the layers of the circuit can debond, and you loose the signal. After it cools a little they come back in contact and it works again. This doesn't go on forever. It will eventally fail completely, if that is the problem.

The actual debonding is caused by vibration, not heat. Make sure you have a good, solid sensor mount.

WERK I · WERK I's Garage

Quote:

Originally Posted by Speedy Squirrel

The actual debonding is caused by vibration, not heat. Make sure you have a good, solid sensor mount.

I agree. That and people put too much clamping pressure on that poor lil' sensor.

This will crack the dielectric and doom it to failure.

zcoker · 03-30-2009, 03:50 PM

Thanks guys for the input. It is not so bad stalling, just the site of a 930 Porsche dead at a busy intersection is a pitiful feeling. LOL. I think a new sensor is in order, unless you guys know of a better more robust sensor. I think Motec has the same sensor. What have any other of you guys with the Electromotive done to solve this crazy problem......i know, i know, loose it and go efi......but I will keep it around for a while, for now.

WERK I · WERK I's Garage

If our host doesn't supply Electromotive sensors, go to Clewett Engineering (www.clewett.com).