GP964

Hi All,

Venturing from the 964 side to the 993 for a friend of mine. His 95 993 just dead while he was driving it. Battery is good, car cranks but doesn't start up. It has lots of gas. He even tried playing with relay # R53 DME relay because it was making an odd buzzing sound. So i took my DME relay (#R41) from my 964, tried cranking it, still nothing and still that odd buzzing noise from the relay. So i put my relay back and my car started with ease. He placed his relay #R53 back it cranked, but no start.

Oh btw, we both made sure the Alarm immobiliser wasn't active.

Thanks GP

d993

Here's one thing you might wanna try;
Remove the positive terminal from the battery, unplug the DME and/or DME relay and let it sit for about 30 seconds, plug them back in, replace the battery terminal, and try it.
This worked on a previous 1990 C4, although it may not work on the 993.
I personally haven't had any problems with my 993, which is also a '95 model.
Here's one problem that a friend of mine had with his '89 911 Carrera (3.2) a few years ago:
He used some fuel injector cleaner (about 4 times the concentration). After about 1 hour of driving, the car started losing power and just shut off, and would not restart.
Now he's a dedicated "do-it-yourselfer", so he refused to take in to get checked out, claiming "I'll figure it out".
When he would crank it, no unburned fuel smell, and no spark either.
He changed the fuel filter, O2 sensor, distributor cap and rotor, plug wires, spark plugs, crank position sensor, reference sensor, DME relay, and even swapped out his DME with a spare he had.
Still nothing!
Then, after that, the car spent some time at 2 different shops that work exclusively on Porsches, still nothing. It would not start!
Finally took it to the dealer. They figured it out in 5 hours of diagnosis. It was 2 clogged injectors.
The 2 injectors were completely clogged, and that threw off the timing through the crank position sensor, which threw off the DME, which threw off the ignition and fuel injector flow (even through the other 4 injectors which were not clogged)!!!
Talk about a nightmare trying to figure it out!

d993

Or, you can try your local Porsche dealer if you don't wanna mess with it. I think a diagnostic runs about $80 for the 1st hour.
Sorry, wish I could be more help.
Good luck.

PedroNole

Call Steve W. at Rennsport. 503-244-0990.

TomF

Try measuring the voltage and current across the fuel pump side of the relay while cranking the car over. I sounds as though the fuel pump is dead or is trying to draw too many amps through the relay. As a fuel pump fails, it can cause the relay to buzz...

Steve W. is great source of info, BTW!

cooz

I'll give ya $500 as is....whattya say?

ceboyd

Bob - 95 993/C2

I'm not familiar with the "r" codes but here's a link to what I know does work when it comes to a 95 993.

http://p-car.com/diy/relay/

Tom W

The DME relays for the 964 and '95 993 are intechangeable - I've done it a couple times.

Bob - 95 993/C2

Thanks Tom, and so were the ones from the 944 as that's what they were delivered with but they fail for some reason. What I've always wondered if a "failed" 944 one from a 993 would still work in a 944? I've not heard that discussed.... Logic says no but I don't know what it is that "fails" or becomes non-compatible in them. I've had two failed ones apart and see nothing obvious...no testing done...just lookin'.

TomF

Bob, the failure is really hard to see. I did a ton of research into this a while back with some of the PCA tech gurus. If you take apart the DME relay, you will note that it has two sides to the circuit board. The relay is also a relay for the fuel pump. As a fule pump fails, it can draw more current, and the resulting heat across this side of the relay is too much for the cheap board. If you look closely, you will see that the foil on the board has actually separated from the circuit causing it to remain "open." You can actually fix this by resoldering the offending part of the board. This also is a great fix for a car that eats relays, as my 87 Cab did repeatedly. Porsche is well aware that the relays are pretty much all crap, and I believe that they just want to sell a lot of them. Hope this helps.

Bob - 95 993/C2

Thanks Tom! Are you suggesting that the reason for the failure is a failing fuel pump? If so, how does simply replacing the relay fix the start issue (in my case for several years driving) with no sign of fuel pump problems? Guess now that I said that, it's sure to go!

Happy Holidays!

TomF

As Alan Caldwell (PCA tech guy) suggested to me, fuel pumps often gradually become less efficient and draw more current. Since most Porsche fuel pumps are oversized anyway, a gradual decline in capacity and gradual increase in current draw may not be noticed.

I just re-read your first post, and caught the part about eliminating the relay....oops! Anyway, I just had another thought- are you sure that the immobilizer is deactivated? I have heard of them failing. Also, they can geet messed up when the battery dies. That is the culprit in many cases...