Can anyone give a good description (or picture) of where this G4 - CENTER FRONT BULKHEAD ground point is located. I have read about one of them being "under" the car near the motor/tranny junction?

 

Drop a rock from the two vacuum line bulkhead connector and it will hit the braided ground strap attached to the transmission-side of the lower frame rail (if it had a frame rail). If there isn't one there, look for a threaded 3/8" hole where it used to be.

Dave

 

Go to the area of the cowl/bulkhead where the two diagonal engine bay bracing rods attach. Now look downward. There's a abutment jutting out from the bulkhead, inboard of the starter relay. There should be a couple ground wires at the abutment. I'm pretty sure that's G4.

Fuzzy memory disclosure applies

Cheers
DD

 

I think you are right Doug. I think I did remove a ground beside the relays.

Dave

 

G4 must be the transmission bell housing /engine block point where they bolt to each other, being that they are almost in the center.

the ground strap can be seen below the car.

 

Thanks all.. I will post some pix for posterity if/when I find it

 

I just looked at my own car and there IS a ground point as I described, with two wires. I don't recall what circuits are grounded here; if I ever knew. I couldn't easily get a pic as the area is pretty well obscured.

My gut feeling is that this is the "G4" ground point mentioned in the S57. The description fits.

What electrical problem are we trying to solve anyway?

Cheers
DD

 

No issues at the moment. Just trying to do the obvious good things. I cleaned the points at the top of the firewall on the left and right (probably G5 and G16 in diagram) and I just remembered people had mentioned another point, I assumed G4.

I just got the car late last summer and am finally finding time to do some fun little projects like that, removing the smog pump/piping, cleaning and restoring the breather parts and pipe. Next on my list is to try to assess/fix the vacuum lines in the engine bay, but tough without a lift. I could get front up on stands but I am always a bit leery of being under any car.

I also need to locate a nice step by step diagnostic for resurrecting the A/C. Lots of parts, fuses, etc. in this system but woul dbe nice to have air in the NC summer.

Thanks again - Randy

 

Finally got time at the car this past wknd and wanted to update my original post with some info and pix. I still am unable to see any sort of ground point "under" the car where the tranny/engine mate, but I will look again and plan to get the front up on ramps soon. But the good news is I did find another important ground point that I need to clean up. So below are the four main ones I know about at the moment. LHD 86 SIII regarding my location references. Hope these help others.....

This first one is one I missed initially. It is under the bolt in the center of the picture and this is on the head just below the cam cover on the passenger side nearest to the bulkhead.You can see the main wiring loom I had to move out of the way to see it and take this pix.



This one is obvious. The big battery negative strap.




This is on the bulkhead passenger side right next to the rubber cowl drain tube that you see in the lower half of the pix




And this is on the bulkhead driver side, again right next to the cowl drain. This point still has the factory rubber boot over the bolt and nut

 

those two posts on the firewall on each side of engine are not Earth or Ground points, those are Hot / Positive, (Always Hot) posts.

Watch out! easy to blow fuses if you make contact with Grounds.

The Ground Strap under the car connected to body and engine/transmission in the passenger side is a very large stainless steel strap and easy to see.

 

Yikes! Good to know Jose. Thanks for the clarification.

But very odd to me that they used "brown" wire for a hot point. My German car always has brown reserved for earth/ground.

Thanks - Randy

 

Randy,
in Jaguars the thick brown wires are always Positive / Hot. Even in my 1965 S type they are Hot. One of those wires in the driver's side of the XJ-6 goes directly to the Alternator and in the interior, to the Headlamps switch.

There is another half of the post inside the firewall, same thing with a nut and rubber boot. You can only see them if you remove the blower fan cases.

there is another thick ss ground strap bolted to the transmission tunnel and to the back of the radio. You can only see it when the entire center console is removed from the car.

in theory, this strap could be used from the chassis to the engine if yours is missing. But I am not sure if the length is enough.

 

I found a couple of pictures that may help you Randy. Braided engine/trans ground strap is just above the + battery post and attached to the lower part of the frame, other picture shows the large braided ground strap that is bolted the LH side of the trans tunnel (about 10:30 position as you face forward in the drivers seat) and runs up into the radio cavity. Mine was not attached to anything behind the radio, but I'm going to put it to good use.

Dave

 

I meant the frame ground is just above the + battery post on my test battery that is setting on the floor.

Dave

 

That is it !!!

Aye, be safe when getting down and under. I prefer ramps over jack stands. But, when on the ramp. chock both rear wheels.. P and park brake not enough!!! Don't ask!!!

A lot o issues were resolved on my "lump" by adding a ground cable. Ran from the one on the wing wall adjacent to the bonnet latch to the alternator bracket on my Lt1.

When I made my installation, I lined up the relays on an enlarged rack at the fire wall. I created a ground buss alongside. All ground except one went to the buss. Exception the neutral start inhibitor. thEn the buss to the battery - at the wing wall. all was well for a decade, then???

extra cable fixed it. .

 

Trying not to beat a dead horse, but I am pretty sure the yellow circle is the attach point you mention and the yellow line follows the start of the strap.... but.... where does the other end of this braided strap attach to?

Thanks for one last clarification - Randy

 

in my 1984 it is located as in the picture below. chassis to engine at the bell housing-engine point on the engine side in one of the 13mm bolts that has a nut and washer.
The bolt at the chassis is 9/16ths or 15mm if I remember correctly.

also here's a picture of the radio ground strap, it measures 23" inches long.

If your car does not have the original engine, then chances are this does not apply.

 

Bravo!! I see the light!... and the ground strap.. both ends I will look again when I visit car next, but I don't think I have one. Add it to the list.

Thanks everyone for helping me get this clear

Randy

 

Jose, love that purple carpet. Let's see more.

 

Jeff, it's a beach towel on a table.
i can't afford purple carpet. haha!