85 carrera stalling problem - help

CHA914 · 04-04-2007, 07:35 AM

Hello,

Well, I wanted my first post as a 911 owner to just show off the car, but it looks like I am going to need a hand.

Bought the car about 2 weeks ago, and I have put about 400 miles on it with no issues.

Last night after repacking the front wheel bearings, I took the car around the neighborhood and it stalled on me twice. The first time I was making a slow left hand turn, car died, I thought I had let the clutch out too fast and killed it. It took probably 10 tries to get it started again, which seemed odd. So I drove for another 5 min, and the last turn onto my street the car dies again, this time a slow right turn, this time it was obvious that it just died, I was coasting through the turn and the engine just shut down. But it fired right up after it died the second time.

Finally this morning while going to work, I was pulling away from a light, just put the car into second gear and started to accelerate when the engine died again. I pushed the car into a shoulder and tried to restart it but no luck. Tried to restart it for a good 20 min, but it would never catch. I checked the fuel pump fuse but that didn't change anything. I got the car towed back to the house and of course, it finally started?!?

So, I have done some reading, could this be the DME relay I have read about? What are some tests I can do to track this down? The car felt like it ran out of gas...

Thanks for the help,

Tony

CHA914 · 04-04-2007, 07:38 AM

Also, the car is a ROW car, so I don't know if that makes a difference as to the relays or sensors.

Thanks,

Tony

mschuep · 04-04-2007, 08:39 AM

Have you replaced the fuel filter? Sometimes old fuel filters run ok when you first start the car, then after a while, all the crap starts to loosen up and gets run through the system and the car runs poorly...Let the car cool off, all the crap collects, fires right up and runs smooth until the crap starts to loosen up again...

Cheap fix that should be done anyway if it hasn't been done already.

CHA914 · 04-04-2007, 08:46 AM

Matt,

I don't really see it as a filter problem at this point, because its so sudden and doesn't act like its always having a problem, when it does run it runs normally. But I will add it to the list of things to do soon.

Tony

Nashville84Cab · Nashville84Cab's Garage

Intermediate problems can be more difficult to pin point. I would go ahead and buy another DME relay to rule that out as it is inexpensive and a good idea to always have a spare in the glove box. Do you think the car was stored with an empty/low tank over winter? I had experienced similar symptoms that were caused by possible water condensation in tank... a fuel treatment appeared to have fixed my problem.

Good luck and please keep us posted to your progress. And don't forget to post some pics of your new toy!

scottb · 04-04-2007, 09:41 AM

If I were betting, I'd say either fuel filter or DME relay. Start with the relay...it's a cheap and easy fix.

CHA914 · 04-04-2007, 11:25 AM

I just picked up a DME relay from the dealer, and will put that in tonight.

When I picked up the car it had a nearly empty tank, I filled it up and then ran it down to less than 1/4, and just filled it up again, so I doubt its water in the fuel, but you never know, I am putting in an order with pelican for some odds and ends and will add a filter in there.

I will update this tonight with pics and let you know if the relay makes the difference.

Tony

porsche735 · 04-04-2007, 12:05 PM

Another 2 items to check on these engines are the grounding point on the drivers's side intake and the intake nuts them selves. I have had both issues on two separate occasions. Lots gets grounded through the intake lug. And if the nuts holding the intake down are corroded, that can cause the ground lug to be bad....

Chris

rick-l · 04-04-2007, 01:02 PM

Quote:

Originally posted by CHA914
So, I have done some reading, could this be the DME relay I have read about? What are some tests I can do to track this down? The car felt like it ran out of gas...Tony

[list=1][*]Voltage on fuse 3 while cranking the car[*]Jumper fuse 3 to battery and see if pump runs / car starts[/list=1]That red/grn wire comes from the DME relay.

glenncof · 03:39 PM

Yup, my 1985 had similar problem. Put a jumper on the fuse block to verify pump operation (of course you need to know which contacts). This would be useful in getting out of a jam. (Edit: I had fuse removed for this test.)

Voltmeter on the pump fuse should read 12V briefly (unless engine is running) after turning on ignition/start. It's controlled by DME relay as I recall. Pump voltage will be shut off if engine does not fire up.

rick-l · 04-04-2007, 03:29 PM

Quote:

Originally posted by glenncof
Voltmeter on the pump fuse should read 12V briefly (unless engine is running) after turning on ignition/start. It's controlled by DME relay as I recall. Pump voltage will be shut off if engine does not fire up.

I have not personally verified it but looking at the DME schematic it looks like the fuel pump should run whenever the ignition is in the start position.

Quote:

Originally posted by rick-l
The schematic below is what FR Wilk tells me is in the DME. The fuel pump runs when pin 20 of the DME is pulled to ground energizing the DME relay.

The blue arrow is the direction current will flow when 12 volts from the yellow wire is appled to pin 4 (turns on NPN darlington).

The red arrow is the direction current will flow when the DME detects the engine is running and commands the pump on (also turns on transistor).

Note that either of these conditions will run the fuel pump.

glenncof · 04-04-2007, 04:11 PM

The vehicle is 1985. Mine is also 1985. When problem occured (and another time) it sounded like no gas. There was no fuel pump whine and my fuel pump is at 177K miles (I suspect it also.) Yes, I checked the fuse and wiggled it.

The tests I mentioned I did when I got home. I was able to recreate the intermittance and ordered a relay that day. After replacing relay, no problem for a year now.

CHA914 · 04-04-2007, 05:43 PM

Well, good news and bad news. The bad news is that the relay I got from the dealer is not the correct one, the good news is that I found the problem.

I found a very corroded and loose wire on the positive battery terminal, I tried to chase it back to see where it went but couldn't chase it all the way back just yet. Either way I had to cut over an inch off the wire to get past the corrosion and then put a new ring terminal on it. After this the car starts and runs just fine. I discovered it when I hit a large bump and the car died instantly, so I went looking for loose wires and found it. I am guessing the wire must be the power wire for the fuel pump or DME or ???

And back to the relay issue, I am going to attach some pics, but basically the relay looks to have the proper schematic, but it has blade terminals and mine has round peg terminals also mine has a hold down bracket attached and the other doesn't, is this a ROW difference or did they switch at some point during the years? My relay is on the left and the last picture shows the porsche part# for the relay I purchased:

Lorenfb · 04-04-2007, 06:33 PM

"I have not personally verified it but looking at the DME schematic it looks like the fuel pump should run whenever the ignition is in the start position."

Or when the DME ECM sees the speed sensor.

"is this a ROW difference or did they switch at some point during the years?"

That's a 993/964/944 DME relay (part # also indicates such - 993).
It was never compatible with ANY 911 3.2. Should have ordered
from Pelican Parts.

CHA914 · 07:43 PM

I have ordered many parts from pelican and if Pelican was down the street from me I would have...and I still might, but I was hoping that I could have gotten the correct part today...I guess thats too much to ask from today's dealers...

450knotOffice · 450knotOffice's Garage

I'll say congratulations on locating the problem and now, since time does not seem to be of the essence, order the DME relay from this site and then store it in your glove box for the inevitable day when it does fail.

glenncof · 01:24 PM

delete duplicate post

glenncof · 04-04-2007, 08:58 PM

For sake of completeness...the DME relay is in two stages.

Relay 1 provides 12V from battery to fuel injectors, + terminal on relay 2 coil, and DME when energied. I'll guess it is controlled by ignition switch but did not trace it out, low side of coil to ground.

Relay 2 provides 12V from battery to the fuel pump fuse. The fuse connects to + terminal on pump and - is to ground.

Relay 2 gets 12V on the high side of coil from relay 1 and the low side goes to pin 20 on DME. The DME controls relay 2 by sinking current causing relay to energize (thanks to rick-i pin 20 darlington pair).

Therefore relay 1 must be energized for relay 2 to be energized, but DME controls relay 2, the power feed to pump.

---
Ut oh, corrosion...maybe over charging. Check fluid levels on battery and monitor.