V1 No Start, Was Working

[glantz]

The engine has to properly ground to the frame as the frame is the primary ground. When you paint/powder coat the frame, the engine mounts don’t make a good ground.

You will want a ground cable from the engine/transmission to the frame also. Remember, your spark plugs need a good ground also.

I went ahead and did this last night. I found an extra cable. I connected that from transmission to frame ground (perfect length too). I moved the ground lug back to its position on the transmission. She’s good now.

 

[Gtstorey]

There is no voltage difference between your positive battery terminal and the “ignition” wires that were in the diagram I posted so you can’t have read a voltage on those circuits. You must have been reading voltage between the battery terminal through the probe and into your ground source. Depending on where you were probing, you may have even measured through the coil in a relay to ground, thinking you were on a hot terminal.
I haven’t used power probes much and mine just does different color for positive or negative current direction, but they seem to be easy to confuse what is going on. I use mine for quick checks, but use a multimeter to confirm what is going on.

 

[glantz]

Yeah I have to admit that I don’t fully understand it. The testing that I did was effective in isolating the problem though. It’s reproducible so I’m confident of the cause. I don’t know. I did measure all 4 power sources to the ecm with key on. All had 12 except pin 73 on x1 and it’s corresponding fuse/receptacle. Pin 73 on x2 is the ground for ECM and that traces back to the ground that was bad.

 

[Gtstorey]

If you were reading voltage from the battery positive through a bad ground it would read the reduced voltage.
Basically what the reduced voltage is telling you is that you have elevated resistance in the circuit between the positive and negative battery post. One of the keys to diagnosing these issues is to figuring out how to determine which side of your voltage measurement the increased resistance is.

 

[glantz]

Yep that makes sense. Thank you again Gtstorey! Couldn’t have done it without your help with diagrams, direction on where to look and explanations. I have learned so much through this experience. Despite some frustrations it’s been an absolutely awesome project. I have always done my own work/repairs on cars but never a project like this. I’m absolutely loving it. The other builders on this forum are amazing too. Hopefully I’ll be able to help someone else here someday and pay it back.

 

[Esstover]

Perhaps a 2006 diagram would work better.

Thanks Ross. I got is sorted. the previous owner had it in the shop and when it go put back together they had to plugs swapped. Pretty surprised that is even possible, but it is.

 

[ah.b.normal]

Two wiring harness plugs? And which two plugs is it even possible to swap?? Though I am sure some multi-plugs can be forced together!, I've seen gorillas at work. I am really curious which two connectors are close enough to each other AND so similar that they can be "hammered together"! As these cars age, the experience and expertise of the tech's working on them dwindles to 0.00, leading to this kind of trouble. I'm all for learning and experimenting but there is no replacement for experience.

 

[Ross]

Oh, there is some plugs that swap.

 

[Robinjo]

Oh, there is some plugs that swap.

I did the same thing. I now have them marked with color tape bands to tell them apart.