Calling 964 experts...

[mjshira]

would appreciate your review of this thread

"Strange no start issue" on the 964 forum on Rennlist.

Thanks

[bazar01]

Where is the link?

[mjshira]

http://forums.rennlist.com/rennforums/showthread.php?p=4770600#post4770600

[bazar01]

It looks like you have a lot of work ahead of you.
Is this for the GP white 964 you are working on?
That will be a nice one once you get it up and running

I'll start with +12V to DME computer and injectors.
Do a continuity test on the following +12V wires to make sure there is no break in the wiring harness.
From DME relay socket pin 87, to DME computer pin 37.
From DME relay socket pin 87 to each fuel injector terminal.
If there is continuity on all, then you are ready to do a test for spark and fuel.

To check for spark, jumper DME relay socket at terminal 30 and 87.
Check for spark at the plug or at the coil wire while starting the car.
If there is no spark, you need to do a continuity test on the ground path of the ignition coil thru the ignition control unit.

To check for injector pulse, use a noid light on the injector harness.
If there is no pulse, check for continuity from other terminal of fuel injector to DME injector output terminal for each cylinder.

[mjshira]

Originally Posted by bazar01

It looks like you have a lot of work ahead of you.
Is this for the GP white 964 you are working on?
That will be a nice one once you get it up and running

I'll start with +12V to DME computer and injectors.
Do a continuity test on the following +12V wires to make sure there is no break in the wiring harness.
From DME relay socket pin 87, to DME computer pin 37.
From DME relay socket pin 87 to each fuel injector terminal.
If there is continuity on all, then you are ready to do a test for spark and fuel.

To check for spark, jumper DME relay socket at terminal 30 and 87.
Check for spark at the plug or at the coil wire while starting the car.
If there is no spark, you need to do a continuity test on the ground path of the ignition coil thru the ignition control unit.

To check for injector pulse, use a noid light on the injector harness.
If there is no pulse, check for continuity from other terminal of fuel injector to DME injector output terminal for each cylinder.

thanks. I've done the check on connectivity From DME relay socket pin 87, to DME computer pin 37. that checks out, but only with a jumper in place, doesn't work with any of the three DME relays I have in place.

[mjshira]

and yes, this is the white car I've been working on. I am trying not to get discouraged...

[bazar01]

Originally Posted by mjshira

thanks. I've done the check on connectivity From DME relay socket pin 87, to DME computer pin 37. that checks out, but only with a jumper in place, doesn't work with any of the three DME relays I have in place.

If it checks only with jumper installed, then the DME ECU is not providing the ground path for the DME relay coils.

There are two coils inside the DME relay. First coil pulls in contacts at pins 30 (battery) and 87 (DME ECU and injectors). This coil is supplied with 12V at terminal 86 thru ignition switch. The ground is provided by the DME computer, but not sure which terminal while engine is started or running. The DME must detect that the engine is turning over at a certain rpm. So make sure also that the refrence sensor is good and gapped properly.
Also check to make sure you have battery 12V at pin 30 in the DME socket.

Second coil pulls in contacts at pins 30 (battery) and 87b (fuel pump). Make sure you have battery 12V at pin 30 at the socket side. If you do, and the fuel pump is not getting power, then the DME ECU is not providing ground path for the first coil at terminal 85 and second coil at terminal 85b.

[mjshira]

great info, thank you. where are these grounds provided? I don't see a ground for the DME itself (physical wire) located where the DME is installed. but what you described above makes sense logically. I am just a newbie when it comes to electrical stuff so I'll need to have some basic instructions and time to work through this. but if this ground was working on again, off again and then I fully disconnected the battery and removed the DME, that might have been the straw that broke the camels back, so to speak.

[bazar01]

Can you get hold of the DME computer plug pin assignment and post it over here? It should tell us which terminal provides the ground path for the two coils inside the DME relay and the final stage output for the two ignition control units that provide the switching ground path for the two ignition coils to provide the high voltage spark. You need spark, fuel, air and compression to fire up the engine.
Did I make it more confusing?

[mjshira]

Originally Posted by bazar01

Can you get hold of the DME computer plug pin assignment and post it over here? It should tell us which terminal provides the ground path for the two coils inside the DME relay and the final stage output for the two ignition control units that provide the switching ground path for the two ignition coils to provide the high voltage spark. You need spark, fuel, air and compression to fire up the engine.
Did I make it more confusing?

here you go...

here is what I don't understand: if when I jumper position 3 and 5 under the DME relay, this puts power to the DME. But here is the thing, when I did this, the DME still didn't energize and or signal the coils because when I left the jumper in place, I still couldn't get the car to run... so this has to be either ground issue because I've tested it with another DME... right?

[dad911]

Not an expert, but double check all of the pins on the DME connector, and make sure none are pushed back too far to make contact. I had that problem in a 3.6 conversion that drove us nuts.

Also, I see you tried another DME in your car. Did you try your DME in another car to make sure it works?

[bazar01]

We should tackle your no-spark issue first.
Check for proper power supplies and ground points on the DME computer plug.
Pin 18 - you should see +12V batt all the time.
Pin 37 - this is switched +12V coming from DME relay pin 87. (ignition ON)
Pins 2, 14 & 24 are all ground points. Use a meter set to ohms. Should be less than 0.2 Ohm. Put one probe on the DME pin and other probe on chassis ground.

[mjshira]

Originally Posted by bazar01

We should tackle your no-spark issue first.
Check for proper power supplies and ground points on the DME computer plug.
Pin 18 - you should see +12V batt all the time.
Pin 37 - this is switched +12V coming from DME relay pin 87. (ignition ON)
Pins 2, 18 & 24 are all ground points. Use a meter set to ohms. Should be less than 0.2 Ohm. Put one probe on the DME pin and other probe on chassis ground.

did you mean to mention pin 18 twice?

I can tell you already, that I don't have power @ pin 37 with the key on. The only way to get power to position 37 was to jumper the DME relay at the fuse panel. I did this, but even when done, the car won't start. But I did hear the fuel pump running. I think, if I understand the DME relay function enough, that if any of the three grounds at the DME relay (the smaller blades on the relay) are not good then the DME relay wouldn't perform its full function and the car wouldn't start.

The DME relay is good, I have three functional DME relays and I've tested all of them with the same result.

So keeping in mind that this all started when I removed the DME itself and changed the chip, I think a ground was disturbed 'somehow' during that process. I am just not sure 'where' or 'how'.

does that make any sense?

[bazar01]

That was a typo. should be pin 14.

If the only thing you did was pull the DME out for a chip change, dad911 could be right. There could be pins in the DME pug that were pushed back and not making contact or the chip is bad.

Did you check to make sure those 3 ground points are good?

If you can get power at pin 37 with a jumper on DME relay and still no spark, move to the ignition coil.

With ignition ON, check for +12V at the ignition coils black wire.

[mjshira]

I check the pins in the DME side of the story. I made sure all were clean and straight. The part that makes me think it is a ground is the fact that if with the DME relay jumper in place, the DME itself doesn't send a signal to the fuel injectors or coils. I have checked this for the fuel injectors and will check it with the coils next.

[bazar01]

Let's check for power supplies and grounds first before we go to the ignition and injector signals.

Do you have +12V to the two ignition coils at the black wire?
You should also get +12V at the other coil terminal with green wire.

[mjshira]

I will check that tonight, I assume that is with the key in the start position?

[bazar01]

No, just with the ignition switch ON.

We're making sure you have all the needed power supplies even if you have to use jumpers on the DME relay.

Once you get spark and get the engine running using jumpers on the DME relay, then your next step will be providing power to the DME relay without the jumper (defeating the immobilizer/alarm/security).

[mjshira]

so you want me to do these tests with the jumper in place?

[bazar01]

Originally Posted by mjshira

so you want me to do these tests with the jumper in place?

No, sorry, you already did that testing 12V at pin 37.

You will need to check the presence of ignition coil +12V with ignition switch ON.

Then check +12V power at the injector plug.

Once all the power supplies have been checked out good, you are ready to try starting the car with the DME relay jumper on and check for spark and injector pulse.