911 3.2L G50 - DME issues

[JonasJMac]

1989 911 Targa turns over but won't start. Have had to have it towed in twice in past 6 months
1st time was told reference mark sensors and cylinder head temp sensors, replaced,
worked great for month then same problem , turn over but no start
2nd time was told replace fuel pump install new fuel filter and pump fuse and replace fuel pressure regulator
great for month now today, turns over and no start
any thoughts, assuming since it's targa likely dme is worn out due to weather/wet,

Thanks in advance

[GaryR]

Originally Posted by JonasJMac

1989 911 Targa turns over but won't start. Have had to have it towed in twice in past 6 months
1st time was told reference mark sensors and cylinder head temp sensors, replaced,
worked great for month then same problem , turn over but no start
2nd time was told replace fuel pump install new fuel filter and pump fuse and replace fuel pressure regulator
great for month now today, turns over and no start
any thoughts, assuming since it's targa likely dme is worn out due to weather/wet,

Thanks in advance

Take your DME out, send it to Ingo Schmitz (Pelican) and he will go though it checking everything and re-soldering those old connections. He has the setup to test it out and is VERY reasonable.

[kidrock]

have you replaced the DME relay yet?

[msterling]

+1 on the DME relay. Most 3.2 Motronic owners keep a spare DME relay in the glovebox. Even I do this. It also could be the DME itself and yes they can be rebuilt.

Seems like you have a lot of new parts that replaced ones that were not bad.

[GaryR]

I assumed, since he replaced all his sensors, he had replaced the DME relay 1st thing... but if not do that next!!

[JonasJMac]

Hey all thanks for replies. DME relay was first thing done( less than 4months ago). Can't imagine it's that again

[GaryR]

Originally Posted by JonasJMac

Hey all thanks for replies. DME relay was first thing done( less than 4months ago). Can't imagine it's that again

Ingo is your next step, too many circuits in that DME that will make you crazy if just one is faulty..

Here is just one joint he found bad in mine..

[blue911rsr]

Could be your alarm control unit was the problem in my car you can remove it and jumper the connector and see what happens no parts required just some time

[Quicksilver]

Stop replacing things and start testing them. All the stuff on the car can be tested.

[SilberUrS6]

Originally Posted by Quicksilver

Stop replacing things and start testing them. All the stuff on the car can be tested.

I was thinking the same thing. Repair shops these days don't make much money troubleshooting - they make money on replacing parts. Besides, replacing parts is easy compared to tracking down intermittent problems. Easy, more profit, return customers (due to the same problem), excellent business model.

This guy also needs to find a new shop. This one is screwing him.

[kidrock]

Originally Posted by blue911rsr

Could be your alarm control unit was the problem in my car you can remove it and jumper the connector and see what happens no parts required just some time

Yup, this too. Often overlooked. Ask me how I know.

[JonasJMac]

Stupid question, but how exactly do you get the DME out, I'm going to tackle this in am and look at everything but can you have full access without taking driver seat out. There is a great video about 944 and they say 911 is similar on ecu doctors but there the DME is behind passenger foot well. Thanks for helping a total newb!

[kidrock]

You have to take the driver's seat out to take out the DME. Very simple, it's held in by 4-6 allen head bolts (I don't remember the size offhand).

Slide the seat forward as far as it can go to access the rear bolts, then slide it back all the way to access the front bolts.

There are some cables to the bottom of the seat that operate the electric seat adjusters. I don't bother disconnecting them to pull the DME, I just slide the seat out of the way a bit. IIRC, the DME is mounted with 10mm nuts and the main connector cable.

[SilberUrS6]

Originally Posted by kidrock

You have to take the driver's seat out to take out the DME.

Did you mean to say "don't" in there? In my 3.2, I did not have to remove the seat, just move it fore and aft as you say in your instructions. IIRC, there were four allen-head screws holding the thing down, BUT, I could be mis-remembering.

The cable connection was a little tricky due to the retaining tab, but it became clear as I was messing with the connector.

[msterling]

Yup, No need to remove the seat. Remove the bolts and disconnect the cable. A 10 minute job.

[Quicksilver]

The test for the DME is to take the suspected bad DME and put it in a known good car. If the car continues to be OK it isn't the DME.

DO NOT test by putting a known good DME into a car where there is a question. There are component issues that can take out a DME. For example a shorted ICV can damage the DME.

[yazhound]

Have you checked the barrel connectors inside the box that you plug the relay into? I had similar problems and the barrel connectors that attaches the hot lead to the relay was quite corroded. Found this after having DME reflowed and new relays swapped. Good luck!

[GaryR]

Originally Posted by yazhound

Have you checked the barrel connectors inside the box that you plug the relay into? I had similar problems and the barrel connectors that attaches the hot lead to the relay was quite corroded. Found this after having DME reflowed and new relays swapped. Good luck!

Anyone have a picture of the way the DME and DME relay are set up/mounted in the car? I want to make sure I have everything I need on the wiring harness the shop gave me with the motor...

[msterling]

It looks like this. Kinda crappy pic but the only one I found. #1 is the DME and #2 is the relay. Big connector is on the front.

[GaryR]

Thanks, i'll look again at the harness, it may just be sitting on there but it looks like the receptacle is very close to the end of the large DME connector, one would think I would notice that! Whats the round thing, seat belt buzzer?