Grounding through throttle cable, Return spring burned the crap outta me! - SOLVED Options

[clapeza]

Got the FI back in my car (1970 1.7L) and working recently. The PO had cut the throttle cable for the carb conversion, so I installed a new TerryCable.
I noticed that the throttle cable got hot. I figured that the ground strap was corroded or broken (I can see it, but can't get to it now.)

I installed a new ground from the rearmost engine case bolt to the battery ground stud on the passenger side of the engine compartment. I used a generic 4 ga battery ground cable from my FLAPS. One end is on top of the battery ground cable. The other is on the bolt that holds the oil bath air cleaner "shelf". This end of the cable is sandwiched between 2 washers on top of the shelf arm that the bolt goes through, with the nut holding it all down tight.

I cranked the car and it ran easily, and the throttle cable was no longer hot, or even warm. Success? Not so fast...

I then replaced the bushings in the accelerator pedal bracket, so it's nice and smooth now.

Didn't get a chance to crank it because I ran out of time that day.

I cranked it today, and blipped the throttle by hand on the throttle body. I thought I saw a tiny spark at the throttle return spring where it attaches to the rear wall. I touched the spring lightly with my finger and burned the crap out of it! The engine had been running only about 10 seconds at this point.

What gives?

Theory: The new accelerator pedal bushings improved the electrical connection to the body. The new grounding cable isn't making good enough contact to the engine case, so the engine is still preferring to ground through the throttle cable.

Assumption: A 4ga cable connected from the engine case straight to the body where the battery connects is an equal (if not superior) ground compared to the transmission ground strap.

I still plan on inspecting and possibly replacing the transmission ground strap, but I'm curious as to why I burned my finger...

Ideas? Advice?

[IronHillRestorations]

Was the transmission or engine case painted? Just to test , clamp one side of a jumper cable on the battery -, and the other to the engine case and see if you still get voltage at the spring