[Jens Ove]

A while ago the car would not start. I had just been driving a short trip, after the car had been not used for a couple of months. After the trip I washed it (not the engine). After that it would not start.

There was some moisture inside the car, because it had to be out in the rain for 2 months while I fixed the garage.

I replaced the DME relay, as I had a new one ready.

I also replaced the flywheel sensor. All fuses in the main fuse box were checked. Still no start.

There are no ignition sparks, and no fuel from the injection nozzles.



I got a diagnostic set from Durametric, and I could communicate both with the alarm and airbag modules, but not the Motronic module, the engine control unit. I asumed it was broken. So I handed it over to a local electronic repair store. The man there could not find any broken components in the module.

Back to the car I checked the voltage pins at the large DME connector (the car side), both 12V+ permanent and ignition, and ground. But everything seemed to be ok. Still I could not communicate with the unit.



Today I received a 100% new DME unit, with same part number as the original. Plugged it in. Still no communication with Durametric diagnosis. And the engine is still dead.



What can be wrong? Any clue...?

All suggestions are appreciated.

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[DaveN]

Never having used a Durametric I might hazard a guess. I know the home version only talks to 3 serial numbers and that's all. Maybe the one you have needs to be reset as it thinks it has seem 3 different vehicles already. Flash can answer this better probably.

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[flash]

how is the DME relay? i'm not sure it will communicate with out that, since that is what turns it on.



also, to communicate with the durametric, you need to activate the software AFTER turning the key to the on position

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[Jens Ove]

The Durametric communicates with the alarm and airbag unit, but not the engine unit.

Believe me, - I've tried numerous ways, includig activating the software after turning the key in the on position.

Still - never got communication with the Motronic DME, and engine is dead.

I changed to a new DME relay. That was the first I did, as I wrote :-) I've also checked the function of the DME relay by connecting it to a battery. Seems allright.

The engine units get its power, as I checked all voltage with a meter. Permanent voltage and ignition key voltage.

I don't know what more to check... I've no more ideas....

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[flash]

when you activate the software after turning on the key (and it won't work any other way) does the green light on the cable light up?

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[Jens Ove]

[quote name='flash' timestamp='1330471127' post='122525']

when you activate the software after turning on the key (and it won't work any other way) does the green light on the cable light up?

[/quote]

Yes it does. Flashing and stable green.

In the program, three different units are available in a tree structure. On top the engine unit. Then the airbag unit and alarm unit. When I click on the airbag or alarm unit, I get connection and current staus. When clicking on the engine unit I get a "communication error" status on the unit.

Of course I cannot communicate with any of the units without the key ignition switch set to on.

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[vliegwielolaf1234]

There has been someone with a similair problem . everything seemed allright but car would not start .

Turned out that the conections in the fusebox did not connect to the dme relay in a propper way

I would bypass the DME relay with jumper wires in the fusebox first, see if that makes a difference .

Also check your ground wires , there is one on the back of the engine left near firewall , i would check all ground wires for that matter , bad ground wires can cause a lot of strange issues .

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[Jens Ove]

[quote name='vliegwielolaf1234' timestamp='1330503102' post='122530']

There has been someone with a similair problem . everything seemed allright but car would not start .

Turned out that the conections in the fusebox did not connect to the dme relay in a propper way

I would bypass the DME relay with jumper wires in the fusebox first, see if that makes a difference .

Also check your ground wires , there is one on the back of the engine left near firewall , i would check all ground wires for that matter , bad ground wires can cause a lot of strange issues .

[/quote]

Your advice seem reasonable. I've thought about the same, - to measure the input voltage and grounding to the Motronic unit when it should be on, and there is load on the wires. Then I need to connect to the cable from the unit. Maybe just penetrate the wires by a needle, and then to my Fluke.

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[vliegwielolaf1234]

[quote name='Jens Ove' timestamp='1330506295' post='122531']

Your advice seem reasonable. I've thought about the same, - to measure the input voltage and grounding to the Motronic unit when it should be on, and there is load on the wires. Then I need to connect to the cable from the unit. Maybe just penetrate the wires by a needle, and then to my Fluke.[/quote]

it's worth a try .

Other thing , alarm systemis in same place as ecu . Never had trouble with this one but it could i guess .

Then i changed the ignition switches on cars before , for simmilair reasons as your , hard or no starting .

I am really guessing here but who knows.



About grounding i would use a couple starter cabels an cinnect them in differnt places at the engine , and then connect them to the negative pole off the battery or some clean metal parts of the body .

Dont risk grounding ecu the wrong way , you might destroy it .

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[flash]

is the connection to the communication port via a multi-pin connector, or the 4 individual wires?

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[Jens Ove]

[quote name='flash' timestamp='1330527052' post='122536']

is the connection to the communication port via a multi-pin connector, or the 4 individual wires?

[/quote]

I use the multi-pin connector that is included in the Durametric diagnostic kit. It fits right into the car's diagnostic plug.

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[flash]

hmmm - ok - i used to have an early one that was individual wires, and thought maybe those might have gotten mixed up. ok.



if the computer is not talking to the DME, and you've tried a different and known good DME, then there is likely a wiring issue. that sucks.



what changed since the last time the car started?

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[Jens Ove]

[quote name='flash' timestamp='1330529165' post='122538']

what changed since the last time the car started?

[/quote]

Really nothing is changed. I went for a drive. Parked it for an hour while I washed it (outside). Then it would not start. That was several months ago. Its been inside the garage since that happened. I've tried to start it several times. Yesterday with a new DME. Unused unit. Nothing. I guess the power wire or ground connection to the DME may be some way bad, so that when there is load (DME connected), the DME does not get enough currency to work. When the DME is disconnected, the voltage (permanent and key) and ground is allright on the connection pins.

It is a little worse to measure the voltage and grounding when the DME is connected and should be on. I need to find the correct wires and connect into their cores with some needles. That's my current plan.

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[Jens Ove]

Today I connected to the wires of the Motronic DME, to pin 18 (perm.+), 24 (ground) and 27 (key +). That way I could measure the voltage with the DME connected.

The result: Permanent 12V is normal when key off and key on. The key switch gave 12V from DME relay to pin 27. Voltages measured between the + wires and the ground wire. There were no significant voltage drop. I got 0.3V drop between pin 24 ground and the car chassie while running the starter.

I also connected the battery in parallell to the battery from a different car (with running engine) while testing, to keep the voltage up.

No solution.

Any idea?

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[craigawoodman]

Could it be that the alarm has triggered the imobiliser function, or that you need something within the alarm function to allow the car to start?



If you are getting power into the DME unit, check the output pins to see if you are getting voltage out - if this is so, then there is a problem on the car side of the wiring.

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[Jens Ove]

I have finally had time to work on the 968, to find the reason why it is not starting.

Now I used a 3-wire connection instead of the DME relay, and the car started...! The old Motronic was allright. I's sad that I did not try this a long time ago. It would have saved me $1000 for the new Motronic unit.... :-(

The problem is that the first coil in the DME relay does not get currency / voltage at pin 86. So the first DME switch never closes. This first switch starts the Motronic unit.



According to http://www.clarks-ga...ual/fuel-16.htm

"All 944s and 968s - Terminal 86

If no voltage is present, the ignition switch is bad, there is a problem with the alarm system (if equipped), or there is a broken wire between the battery and ignition switch, between the ignition switch and alarm module (if equipped), or between the alarm module and fuel pump / DME relay. If equipped with an alarm system, bypass the alarm system using ELECT-23, and repeat the test. "



So where should I start? Anybody who had problems with any of these 5 possible wire connections / locations? I have the wiring diagram, but I cannot see these wires there. Where and how can I find them?

The alarm module responds to the Durametric diagnostic tool, and seems allright.

When turning the ignition key switch on, I get normal lightning on the instruments. Does the ignition switch have a twin switch dedicated for the DME only?

I will be happy for any help or suggestions.

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[Jens Ove]

The problem is finally solved.



I was preparing a secondary relay unit to supply pin 86 on the DME relay, using an extra relay and a circut breaker located in the coupe. I was not sure if I could use permanent 12V, so I prepared to connect it to the ignition breaker circuit. I just HAD to make the car running, so this should make it possible to start it before solving the wiring problem...



I connected a new wire into the red-yellow wire from pin 86 under the DME. I had a lot of struggeling with the central electric system, because I had to disconnect two of the large connectors underneath it to be able to connect a wire to the red-yellow wire there. I disconnected the connectors, and another connector on the opposide fell out. It was a fight to get them all in and close them by the center lock. I finally succeeded.



When i was connecting a secondary relay to the new wire from DME pin 86, I discovered that the wire now had got permanent 12V. I inserted the DME relay, and the car started. No home-made secondary relay was needed. The car had fixed itself :-)



I believe that there were problems with the connectors underneath the central electric system, and when I struggeled with them, the missing connections got connected.



From now on I will keep a DME bypass wire in the car in addition to a new DME ralay. Because a new relay will not fix such kind of problem, but the wire will.



Thank you for all your help! :-)

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