Jman2678

I'll check that area as well and see if I can't find anything. Battery terminals are relatively new, however I will give them a scrubbing today!

Update: Couldn't find a grounding point under the dash, however MP IX and MPVIII have now been cleaned again to no avail.

931guru

As you requested yesterday, here is the pinout and wiring diagram of the DME/ECU for the early 944 cars.

931guru

Here's maybe more of what you are looking for as a pinout...

Jman2678

That’s absolutely fantastic 931Guru, thank you!! My thinking now is to verify whether 12v is coming straight out of DME which should either rule out everything in between or confuse me greatly. Any other suggestions?


EDIT: After thinking this over while at work today, I'm thinking I'm not on the right path with this. We already know that the DME is cutting power specifically to these injectors, and not others. So that means ground and 12v are good. I think it's just a matter of why is the DME refusing to power them(aka is it due to high amperage or shorted injector).

Jman2678

Just making a separate post for this update so I don't have to double edit my last one. I believe my problem is specifically the injectors are drawing too much current, or there is too much resistance when the injectors physically fire(idk if this is true in any way, just using the forum as a sounding board at this point). Thinking about solutions to this problem, I believe I should manually ground each injector, to be absolutely sure they are clicking. My reasoning for this is one of the injectors could be stuck, causing excessive resistance(again I have no idea if that's how this works or not) that then triggers the DME to cut power to them to prevent overheating. Sanity check?

UPDATE: I was just too curious to call it a night so I went out and fired each injector manually. They all clicked nicely. Fooled myself by trying to start it after that, only for it to start up due to the fuel I sprayed when I fired them manually, then nearly immediately died :'(. Got my hopes up just to crash them down. Which leads me to my only questions, is it possible for somehow my injectors are being undervolted? I know very little about electronics, but from my understanding is amps=watts/volts. I can't change the wattage of the injectors(at least to my knowledge of what wattage is), the only real variable there would be voltage. As I understand if watts stay the same, and voltage lowers, amps increase. Maybe it is just a bad 12v connection somewhere causing voltage drop to the injectors? I don't know at this point. Any pointers on a next step would be greatly appreciated. Also just wanted to mention, so no one has to ask, I do have tach bounce with the injectors that are not firing. Also, is there any way to tell if the DME is having a bad time with high impedance injectors, as I think about it I could always just add resistors inline with the injectors to get the system to the same resistance of the previous injectors that work just fine. I just REALLY don't want to do this without a way to monitor the DME to make sure no damage is caused. Obviously I'd rather figure out the why and fix it, but fed is fed if I'm not able to figure it out.

orig944

No, it doesn't. If the ground sucks, or more importantly the 12V sucks, the injectors may not fire correctly even if the dme tells them to. Alternately, if the 12v power through the dme relay to both the injectors and dme is compromised, the voltage drop caused by the injectors firing may cause the dme to be constantly resetting. The DME ground, the injector ground, the black/red wire from the battery to the dme relay are all suspect.

Jman2678

This morning I went through every grounding point and tested continuity from the point to negative terminal on the battery. I got less that 0.1 ohm resistance on each one. I have 12v on both sides of injectors with key turned to on position. When cranking, 12v at injectors nearly instantly drops to nothing.

EDIT: I will be checking 12v supply from DME relay to injectors/DME again. I forgot to include it in my post a few days ago, I already checked it but since I can't remember(I have some memory issues due to TBI from a VBIED) I'll check again and update in a little while.

Zirconocene

Do you have someone close to you with one of these cars, where you can borrow the DME to test it out? I don't remember if you've already done something similar to rule that out, so apologies if that's suggesting a dead end.

Focus 9 offers upgraded, replacement DMEs, if you find that's the issue.

Cheers

Jman2678

Not that I'm aware of, I'm in the Dayton area in Ohio. I know of one other 944 owner around here and his hasn't ran in a long time specifically due to DME issues so I'm not sure I'll have luck with him. Is there a place on this forum that would be useful to try to find someone near that might be able to help? I've been lurking on the forum for a while but I typically don't actually get involved.

Zirconocene

From memory, there's definitely folks that are active on the forum in your area. Maybe if you want to give this a shot, a new post asking for that specific help would get some eyeballs on it.

Cheers

Jman2678

Thanks for that Zirconocene! I have an update and unfortunately it seems that it's more than likely an issue with one of the injectors themselves. I spoke with the manufacturer and they're sending me a new set. They're going to physically test them in a car before sending them that way I have actually known good injectors and can troubleshoot from there. It's just too difficult to troubleshoot without knowing if an injector was just DOA. I told the wife this is why I need a second 944, so that I can swap known good parts, she disapproved . I'll update as soon as they get here, hopefully should be Friday at the latest.

Jman2678

Small update, I'm still just not sure what the problem is. I checked 12v supply from DME relay to injectors and it checked out just fine. 12v when key is in run and cranking. I checked resistance from DME ground to known good ground with less than 0.1 ohm resistance. Anyone have a next step I can try?

orig944

I don't understand these two statements. The DME does not supply 12V to the injectors, the DME relay does. What were you measuring in the second statement?

Jman2678

As I said originally, I checked 12v supply from DME RELAY to injectors. IE red/blue wire that goes from the DME RELAY to the fuel injectors. When the key is in the run position, I have 12 volts. When cranking, I also have 12 volts. If the car begins to start, or cough, voltage to the injectors instantly drops to 0.

931guru

The DME RELAY provides 12 volts to two places...1) the fuel pump, and , 2) the DME ECU.

It does not provide 12 volts to the fuel injectors. That is done by the ECU. (At least, as supplied by the factory.)