Please Help a 944 Virgin!

[William Miller]

Helping a friend resurect his father-in-law's 1983 944.
I've never had a reason to wrench on a 944 so I offered to help, mostly for the learning experience to see for myself what all the fuss is about.:bang:

OK, maybe some good karma will come my way.............

Towed the car home a few weeks ago and spending a little time here and there.

Was told that the car was overheating so they stopped driving it. Several years ago. The last attempt to start it failed maybe a year or so ago.

The overheating seems to probably be a stuck t-stat from what they described.

So Far:
Drained fuel tank and replaced fuel filter.
Charged battery.
Tried "new" DME relay which DID NOT make the fuel pump run.
Made a DME relay Bypass jumper wire and now have power to the fuel pump and I assume the DME.

Fuel is pumping and pressure looks decent.
Next, still no spark so replaced plugs, cap, rotor, wires (part of the overall plan.)

Still no spark. Probably no fuel without the DME Jumper.

Next plan is to test coil.

Did some searching and read about alarm control unit problems and saw procedures for by-passing the controller. I did this on y '83 SC.
I read that the controller is behind the radio. Do I take the radio out?
(Procedure please or link please)

Next it seems that I should try and swap the dme just to test.
Anyone have a good one that I should try?

Also read something about the tach should bounce.....?
Is this a signal from one of the crank sensors.

I've never had a late 80's porsche. Kind of jumped from the k-jetronic to the 90's with the 3.6 that has some on board diagnostics.

Any help / guidance TOTALLY APPRECIATED!

Thanks!

[Trak Ratt]

Best to start by downloading the manual! Then Clark's garage has great tips! But ultimatley you should prolly just walk away :bang:

[racer]

From what I've heard, the Crank Position Sensor, if damaged, causes a no-start scenario. No doubt located on the backside of the motor and not too accesible. Likely also to be brittle wire and plastic clips, but that is just conjecture.

[hobiecat]

From what I've heard, the Crank Position Sensor, if damaged, causes a no-start scenario. No doubt located on the backside of the motor and not too accesible. Likely also to be brittle wire and plastic clips, but that is just conjecture.

x2 - That can definitely be a factor, but the bad DME relay that was swapped out with a "good" one is troubling.

Best advice would be to work this problem in a logical way and eliminate everything simple that you can - FIRST.

If you're getting fuel at the rail, then at least the bulk of the fuel system is not the problem. The only
thing that you can't easily eliminate are the injectors (unless you have some noid lights)

Check for spark at the coil, but also at all four plugs.

Make sure the battery is FULLY charged as well.

Check for "tach bounce" when you turn the engine over...lack of the bounce is a good sign you have sensor issue.

Oh..and go here: http://www.clarks-garage.com/

Lots of good tips and how-to's in there.

[William Miller]

Thanks guys!
I have downloaded parts of the factory manual.
I have looked at clarks garage but much of the info is for newer models.
I haven't found the wiring diagram for the alarm system yet. I wonder if it's the same part as in my 83 sc. I had a diagram for that somewhere.

No spark using: a spark tester light, a spark plug, and my timing light.
I need to bench test the coil next.

To clarify: I have fuel only when the DME relay is jumped out. The new relay did nothing. I had to unscrew the upper fuse box just to get in there to see the outlet where the relay plugs in.

Could it be a bad ground?
Somewhere I read that there is a ground on the firewall. I found a large engine ground wire. There is continuity between the engine metal and battery ground, but where does the DME ground?


Do I have to take the Radio out to find the Alarm modual?

Thanks!

[William Miller]

Best to start by downloading the manual! Then Clark's garage has great tips! But ultimatley you should prolly just walk away :bang:

My freind has a driveway full of really nice cars that I get to drive from time to time. Just delivered was a Mercedes SL 65 V12 Black Baron. 35 miles on it and he just got the tags. He said it's the fastest car he's ever driven. Way faster than his F 430!

So, walk away..... I think not!

[dhshivers]

There is a ground cable that is attached from the rear of the engine to the fire wall. It acts as a ground for the electrical system. As with any ground it becomes corroded and needs to be cleaned or replaced. It looks exactly like a battery ground cable.

No matter what you do, if this cable is not transferring current the car will not start. It gives all of the symptoms of a bad battery or bad alternator.

How do I know, I've been there.

Hang in there.

[Roxtar]

i have my old coil... free if you come pick it up (culpeper or warrenton).

it was working when I pulled it.

[William Miller]

I'll go ahead and clean the ground terminal behind the engine. Is there a seperate ground for the DME harness?

Roxtar, Thanks for the offer. I'll test the coil and see what happens.
I probably have something that will work if it is bad. Wouldn't that be simple!

Re-read Clark's garage article on the alarm bi-pass and the very last line states that if you bi-passed the DME relay and the car didn't start then the alarm modual is NOT the issue.

Looks like I'm pobably goint to be chasing a DME problem.

Anyone have a spare that I can barrow?

[HoodPin]

x2 on the earlier mention of the crank position sensor. There's a couple of ways it can be a culprit. The sensor itself could be bad. Or the wiring and/or connector could be damaged. Or the magnetic tab on the flywheel could be damaged or missing (especially if the flywheel is partially exposed from the front, as often happens after a clutch replacement because the cover shield isn't replaced). And I believe there may be 2 or 3 magnetic tabs on the flywheel, which provide rpm and/or position information to the sensor.

Another easy thing to check is to pull out the relays and look for any signs of corrosion. Not long ago one of my 944's wouldn't start, and jiggling the DME didn't solve it. I found that the base of another relay (can't recall which one) showed signs of corrosion. I sprayed with some electric cleaner, replaced and the car started. Not 100% it was the cause, but good enough for now.

[VaSteve]

Car overheated and got parked. Why suspect crank postion sensor unless touched or a mouse ate the wiring? Or it fell out. You can see it from the drivers side towards the rear IIRC.

[William Miller]

Unscrewed and tightened the two ends of the engine ground strap. It looked like the engine side had ground terminals from the engine / DME wiring harness. Tried to start after that and no joy.

While starting looked for movement in the tach needle. Got a tiny movement when the key was turned to ignition, but not any sort of "bounce" as the engine was cranking.

Following up on Tony's theory, next I'll unplug the DME and see what the connections look like.

With the alarm eliminated I'm starting to think it's the DME that got fried.
There were all kinds of warnings about jump starting the car. Has anone killed their DME that way?

Anyone willing to lend theirs out?

[smo]

Did the coil test out ok?

[William Miller]

Haven't had the time yet.
Logically it is probably not the coil because without the relay jumped, I have no fuel either.
My uneducated guess is that the DME is fried.

[KevinOyler]

The proper question is can I try my DME in someone else's running car? If your DME is bad, the running car will not start. If your DME is dead, you need to determine what caused the CPU to fail before putting another one in it.

[Potomac-Greg]

Good luck. Seems like a challenge, but you're going in with your eyes open (and at the right price!).

For good BTDT type questions, find the 924/944/968 forum on Rennlist. That plus Clarks-Garage can solve most problems.

[William Miller]

The proper question is can I try my DME in someone else's running car? If your DME is bad, the running car will not start. If your DME is dead, you need to determine what caused the CPU to fail before putting another one in it.


Great Idea, just need to find a volunteer!

[HoodPin]

There are also different DME for different years.

[racer]

Pelican parts lists only 1 DME for the 944 cars.. It costs $25.

[VaSteve]

Pelican parts lists only 1 DME for the 944 cars.. It costs $25.


That's the relay. The DME is the computer itself, no?

[racer]

That's the relay. The DME is the computer itself, no?

Ahh.. now I see.. those are several hundred dollars.. most likely more than the value of the subject 944:shock:

[VaSteve]

True dat!

[William Miller]

Ahh.. now I see.. those are several hundred dollars.. most likely more than the value of the subject 944:shock:

Yup, unless it's sentimental value.

So no volunteers?

I found a DME at a MD junkyard for a buck fifty.
He's willing to gaurantee for 90 days.
But I'd still like a test platfom to test the existing and possibly test the new one.

Anyone up here near Darnestown willing to help out?