I have some electrical gremlins I trying to eradicate, so I'm attacking the grounds first. I've researched the subject fairly extensively, and I THINK I've found them all, but I'm not sure. The one that I'm unsure about is the ground I've seen described as an ECM ground from the harness, and it supposedly connects to the head on the front of the engine on the driver's side. I can't find any electrical connection here, but there is one on the end of, and close to the top of, the block on the driver's side, and since I have an 88 (which could be different from other years), I'm thinking that this may be the same connection. This is NOT the "Trans to body backup ground" that connects to the bellhousing. I found that one.

Is this the "ECM Ground"?

This weekend I went looking for the ECM ground - it was right by the ECM under the armrest.

The primary grounding point for the wiring harness (and ECM) grounding is the second engine to tranny bolt up on the starter side. They terminate on the tranny side under a nut.

There are also two pairs of sensor grounds (G503 and G504) that come from the ECM and attach to two separate bellhousing studs in that area. One pair has a dark green wire and a black wire, and the other pair has a tan wire and a black wire. Both pairs terminate in a huge eyelets.

Edit to add photo:

[This message has been edited by Bloozberry (edited 11-29-2010).]

quote Originally posted by Bloozberry: There are also two pairs of sensor grounds (G503 and G504) that come from the ECM and attach to two separate bellhousing studs in that area. One pair has a dark green wire and a black wire, and the other pair has a tan wire and a black wire. Both pairs terminate in a huge eyelets.

Is this engine an 88? If so, then mine is different. I found one wire grounded at the location pointed to in the photo, and it came out of the harness. At another point on the block (near the top on the side), there's a pair of wires terminated in one of those "huge eyelets". That's the one I was questioning. Where is the 2nd bellhousing stud? You mentioned that two are used, but the photo only points to one.

Yes, it's an '88. When I rebuilt this engine, the second pair of wires were broken so rather than splice on new ends to make it longer to reach the original location, I just shortened them and installed both pairs to the same transmission stud shown in the picture. They are both grounds and it really doesn't matter where you install them unless you want to be very picky about restoring the car exactly as it came from the factory.

quote Originally posted by Bloozberry: Yes, it's an '88. When I rebuilt this engine, the second pair of wires were broken so rather than splice on new ends to make it longer to reach the original location, I just shortened them and installed both pairs to the same transmission stud shown in the picture. They are both grounds and it really doesn't matter where you install them unless you want to be very picky about restoring the car exactly as it came from the factory.

I have no interest in that level of restoration. However, you have 4 wires connected to your bellhousing. I have one, and two more connected to the block. That leaves one missing, and I AM interested in finding that. So, which bellhousing stud is the one that was used, but you no longer use?

The service manual isn't clear, but from experience, the second location is actually on a stud on the transmission-end of the forward cylinder head. I'll see if I can't take a picture of an '88 I have on an engine stand later this afternoon (it's a bit crusty) to show where they should be. The reason the location on the head is not a good place is because of the heat from the exhaust system which is very close at that location.

[This message has been edited by Bloozberry (edited 11-30-2010).]

Bloozberry, thanks a lot. You've been a lot of help. A photo of that connection on the head would be great. I tried to find a connection there, but I couldn't find one. But then again, that's NOT the most accessible area of the engine bay.

Thanks.

OK, here's what the service manual says, but like I said, I had to insert the titles and furthermore, not all G503 and G504's are located where the book shows since some are on the bellhousing as mentioned before.



Here's what I found on my spare '88 engine... interestingly, they're both located where the manual says they should be... and they've been broken and repaired by the previous owner so that all four wires are soldered onto a single larger black ground wire and then attached to the lower of the two head locations.



Here's a close-up (... I warned you it was a cruddier engine! )



Hopefully that clears everything up for you.

quote Originally posted by Bloozberry: Hopefully that clears everything up for you.

That cleared it up great! I found them all now. I cleaned them up as well as I could. Getting to G503 & G504 is ROYAL PAIN on an engine IN THE CAR. They all seemed tight, so I suspect my problem is elsewhere. At least now I don't suspect my grounds.

Thanks for the photos. I searched for several days, and found NO photos showing what I needed. I found several descriptions, but no photos.

You got a + from me. That deserves more than one +, but I can only give you one.

Thanks.