Help with grounding mysteries!

[SRL]

Guys, I've just completed a major project on my stock 1972 911T, well, almost, which consisted of engine/trans removal and servicing/leak chasing, rear window seal replacement, parcel tray rust repair, engine compartment reconditioning, front end rebuild, pedal cluster rebuild, and shift linkage rebuild. I did all the work myself except for the rust repair and engine compartment restoration.

I was super-diligent in making notes, marking parts, and taking photos during disassembly in order to make reassembly easy. Unfortunately, my body shop threw me under the bus a bit - when the car came back from rust repair/engine compartment resto, there were two completely loose ground wires. Now, the only things left in the car when they had it were the fuel filter cannister assembly and the driver side mounting plate that has all the electrical items (relays, etc). I believe they temporarily removed those because they were loose when they came back, so my suspicion is that the ground wires are from there. Let's just say the body shop employees were of no use when asked later about these ground wires.

So, the drivetrain is back in, starter's wired up correctly, transmission ground strap is connected, constant 12V to starter - everything looks good, but a twist of the key does nothing - no solenoid click, NOTHING. I believe these ground wires are the root cause, but I'm not the best with electrical issues. I have a feeling the two yellow wires that activate the solenoid via the ignition switch are the primary issue and that a ground is missing for them....

I'm hoping you guys recognize the wires, using the pics below, and the general area of the car described above. Any thoughts?

Culprit #1: 9-1/2" long, brown wire, loop connector at both ends - one end accepts a stud for a 17mm nut, the other a 13mm. I believe this is p/n 911 612 008 00 (item #22 on page 426 of the PET PDF) - but I'm not sure how it connects.


Culprit #2: 13-1/4" long, braided steel strap, loop connector both ends, each accepts a stud for a 13mm nut.


Thanks in advance....Scott

[Alan.uk]

Hi Scott,
I am assuming your 72 T is a US car as outside the US, the 72 T was on carbs. To me those looks like the engine bay relay panel to earth wires for an MFI car. One goes from the panel itself to the M8 stud at the back of the LH side of the engine bay, and the other (the brown wire) is the earth from the MFI filter housing which is again just behind the relay panel, the 17mm end is from the filter housing at the top and the M8 (13mm) end on to the earth stud. I will look for some pics for you. These alone may not be the cause of the probs.

HTH

Alan

[Alan.uk]

Sorry this may not help much Scott, but just in case. The pic is actually an early 73 RS we restored (hence no engine bay underseal) but it serves the purpose for now. The arrows roughly show the location of each point I previously refer to.
Hope it helps?

Alan

[304065]

The brown one goes between the electrical panel and the filter console

but those things have nothing to do with your failure to have the starter engage
The starter gets its ground from the trans case, and the trans case gets its ground from a copper braided strap between the trans and a stud welded to the body on the backside of the starboard rear seat, on the vertical panel. Make sure that strap is present: make sure there is absolutely no paint or anything else between the strap and the body. Good luck.

[John912]

Scott:

If the starter solenoid has two sets of connection lugs, try putting the wire(s) that activate the solenoid via the ignition switch on the other lug (one on the opposite side of the solenoid). I've had that happen to me once.

[SRL]

Thanks guys....frustrated here....conected the wires like Alan.uk said, AND cleaned/re-installed the trans to body grounding strap....still no-go!

[edmayo]

When you say you have a constant 12v to the starter which wire is that at? The very large black cable is from the battery and will have constant 12v, the yellow 12 gauge wire is from the sign. switch and should only have 12v when the ign. is turned to the crank position. If you do have 12v on the yellow wire when ign switch is in crank position then as john912 said, you are on the wrong terminal of the solenoid. The yellow wire must go to term. 50 on the solenoid.

[SRL]

Ed, the constant 12V is at the large wire coming in from the battery and going to the alternator. I need to check tomorrow for momentary 12V at the yellow wires (my car has two yellow wires that join together with a spade connector - I believe my starter only has one blade that can take that spade connector) when the ignition is twisted to the "start" position.

Thanks for the input.

[Mr9146]

With the key in the ON position you can use a screwdriver to jump across the heavy lug on the starter solenoid to the spade connector on the solenoid and, if it's got power, the starter will crank. If that happens then your problem is with the yellow wire, most likely at the solenoid. Make sure the connector is tight on the spade, and make sure, like Ed said, that it's on the correct spade.

Also, make sure the 14-pin plugs on the circuit panel in the engine compartment are plugged in correctly and plugged in all the way. I've made that bonehead mistake before...

[savaden]

One yellow wire at the solenoid goes directly to the ignition switch terminal 50. Make sure that is plugged in and that you have power to the ignition switch. The other yellow wire goes to the ignition coil relay on the electrical panel. You could disconnect this wire and the starter should still crank. The coil would get lower voltage during cranking, though.

SV