newred944

My newly acquired 1987 Porsche 944 had an intermittent starting problem, I replaced the DME relay and it seemed to work until the problem returned.

Does anyone have any Ideas?

Jfrahm

What's missing when you try to start it? Fuel? Spark? Next time it does not start, be ready with a spark checker and a wrench to check for fuel at the rail (or a can of starting fluid) and maybe a noid light to see if the injectors are firing.

-Joel.

newred944

Well, it didn’t take long for this problem to resurface, their is power to the coil but no spark from the coil to the distributor cap. I believe the DME unit is bad.

TRWright

Try replacing the coil first. Where are you located? Maybe another rennlister can let you borrow a DME so you can see if that is the problem.

Jfrahm

I thought the coil was grounded through the DME, can you see these pulses on the - terminal?
Do you have an alarm that might be trying to disable the ignition? Maybe an aftermarket one?

-Joel.

newred944

tedwright, I live in Essex Maryland. Jfrahm, I talked to the Porsche to said, they think that the DEM unit has to be replaced. I have just ordered one that will be here tomorrow 08/12/2005, I will install it and let everyone know what happens; thanks for all the help so far.

rcarpen22

If you are a fairly competent mechanic then go on www.clarks-garage.com and look at the section on how to diagnose a no-start condition. I used that when my turbo wouldn't start and it took me straight to the correct problem.

Stefan

I have been having a similar problem with my car for 2 years now. The DME relay was changed but to no avail. Here are my symptoms:

- Won't start intermittently when car has been sitting for 30 minutes+ and ambient air temp is ~20C
- Checked for spark and there was none at plug #1 or #2 until it started
- Always starts fine in winter when air is cold, even when sitting for month or more during winter.
- Always starts fine when car is hot (i.e. just running, turn off and turn on again). Seems good on realy hot days as well.
- Once started, runs and accelerates great.
- Alarm has been taken out of car years ago and bypassed.

At first I thought it was a fuel issue or temp sensor until I found that there was no spark.

I will be swapping the DME as well and see what happens. The only things my mechanic could suggest was that or the Reference mark sensor on the flywheel. I can't see how it can be th DME, but I have no more options left.

Let us know if your DME switch works!

Stefan.

newred944

Well everyone, update on the no start problem with my 1987 Porsche 944.
I replaced the DME Relay; I checked the ohms on the coil from post to post and got a reading of 0.6 ohms right on the money. I checked the coil from ground to center got 5.88 k ohms which was in specifications.

I replaced the DME unit and still had the no start situation. I noticed that the harness coming from the DME unit had a wad of tape on it. I opened the tape and find that the ground had been cut and soldered but five other wires had a section of insulation removed and left bare. I re-taped the bare sections and sealed the housing. I will replace the insulation with liquid insulation this weekend.

The car started immediately.

newred944

Stefan

Replacing the DME did not correct the porblem.

Tom Carson

I had similar symptoms (no start after sitting 30 minutes) and replacing the reference sensor took care of it.

Stefan

Appreciate the tip. Was your problem also ocurring only when it was warm out and not in the cooler winter months? This temperature relationship is really puzzling!

Glad you found the wire problem!

Tom Carson

I only had the problem for a couple of weeks...so dunno about the outside temperture making a difference...but it would not be a surprise if it did.