'95 3.6L conversion in 911SC DME/DME Relay issue
 

Been struggling with this for a while. Concern number one at this point is when I turn the key in the on position, the DME relay starts to buzz. I am pretty sure it shouldnt do that. Trying to trace what the problem might be. Seems like a ground issue possibly?

Sidebar: If I pull the original relay out from the fuse block under hood (the red relay) it doesn't buzz, but would assume the relay needs to stay so the circuit stays completed (am I wrong?)

Engine is '95. DME now has a Steve Wong non-immobilizer chip in it now.

What I know:

I have 12v from the battery at the relay posts 30 and 86 with key in off position.
The harness has 12v at DME terminal 18 so there is primary power to the DME unit
With the key on I have 12v at the coils both posts

Without battery connected I checked the following with ohm meter and:
I have continuity from DME terminal pin 37 (s/b switched power) to DME relay 87
I have continuity from DME terminal pin 36 (ground) to DME relay 85
I have continuity from DME terminal pin 3 (ground) to DME relay 85b

The fuel pump circuit seems to be the culprit of the buzzing. Again, it is only when the key is in the on position, and when I pull the original relay out from the fuse block under hood (the red relay) it doesn't buzz, but would assume the relay needs to stay so the circuit stays completed (am I wrong?) Could it just be a bad relay in the old position?

I touched the switched posts of the dme relay with a grounded test light quickly, and the DME buzzes when contacted with that?

Trying to help a friend with this, any guidance is appreciated.

How do I check the flywheel sensor to make sure it is sending a signal (just in case).

Thanks,
Erik

Bump for a good cause, sorry Erik. I don't have the answers your looking for.

All I know is my relays don't buzz noticeably

an Oscilloscope is used to check the signal, the flywheel sensor induces a voltage each time it passes a tooth, this is rarely an issue as it's all solid state magnet and wire w/ no moving parts

make sure your ECU is grounded and with key on, you can run a known good ground wire to 85 and 85b and see if the buzzing continues, if it does, it is not a ground problem. Or you could just run a few jumpers in and out of the relay stand alone and see if it still does it.

I did a 3,6 swap to an '80SC back in 1992, when almost no one was doing then yet. The wiring up of the SC wiring to work with the DME was a big challenge that I spent many hours on! Just got out my old notes on the task ,and tried to remember what I did with the DME relay wiring. The one thing I know for sure, is you DON'T use the red fuel pump relay at all! The DME relay runs the fuel pump directly with no other relay. The DME relay connector 87b runs directly to the fuel pump thru a 15A fuse. (I think it is fuse #16 25amp in the main fuse block on the SC) After looking at my notes, I somehow can't believe all the hassle I went thru, but I was much younger then, and had the zeal!
Grant

Go it to WORK!!!
 

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There was a ground that was taped up into the DME that we could not see. Take a look and listen!

Mad Mike

Mike please tell me how you resolved your issue.

thx-

James

Looks like its a workin. I see flames @ 0:14!