1997 K2500 7.4L Starter S wire repair *Fixed*

[Schurkey]

Starter has been erratic on my '97 454 "plow truck" ever since I bought it six months ago. I finally had time to dig into it.

I found that the "purple" wire to the starter solenoid "S" terminal had been repaired before by the Previous Owner. I don't know who "Previous Owner" is, but he sure seems to cause a lot of problems. The repair was done poorly, and had corroded again. I cut the repair out.


I needed to cut even farther back on the original purple wire to get to good, clean copper-colored wire instead of black and green crappy-colored corroded copper. I cut...and cut...and finally cut to the last accessible section of that wire before it disappeared into the steel-tube heat shield behind the bellhousing. And even that far back, the wire was corroded. (Compare to the shiny section which in real life is still not that great--there's traces of corrosion I didn't want to see!)


The purple wire goes up and over the engine, and connects to a relay box on the driver's side inner fender. The starter relay that powers the purple wire is in the right rear corner. I broke open the wire harness in the most-convenient place, (kinda on the far side of the master cylinder) and probed around for a purple wire. The harness was so stiff that I had to flex it with both hands to get the individual wires to not stick to each other. It's like they were lightly glued together--which ended any hope of using the original wire to pull the new wire through the harness for original routing. To be sure I had the correct wire, I connected my ohmmeter + lead to the relay output socket, and used a wire-piercing probe on the negative lead to test the purple wire in the harness. Zero ohms! That's the wire!


I clipped it, found bright, shiny copper so I crimped then soldered my repair wire to it. I'd have bought purple wire, but my local stores didn't have purple. Red, 12-gauge it is.


I use heat-shrink tubing with hot-melt adhesive on the inside to positively seal out moisture.


Then tape-up the harness, and eventually put the convoluted tubing over the original wires. There was no convenient way to route the new wire inside the harness, so it'll just have to route on the outside, tyrapped to whatever is handy.


My new wire, behind the engine, down the bellhousing, through the little heat-shield tube. I crimped and soldered a ring terminal to fit the "S" terminal stud, sealed with heat-shrink tubing. I polished the terminal for the main battery cable, and the studs on the solenoid. I wire-brushed the aluminum housing of the starter where the bolts go through, and the engine block around the starter bolt holes, so the starter can ground to the block properly. All wires securely attached to the solenoid. Starter bolt threads coated in anti-seize, and torqued.


The original purple wire is taped to the knock sensor wire behind the engine. Then it disappears into a branch of the main harness. DO NOT think that you can fish the new wire through the harness. There is no way on earth you'll pull the new wire from the bellhousing area through the harness to a point that's accessible to splice into. I had to be satisfied with just dropping it down behind the engine loosely, and then route it through the tube bolted to the bellhousing.

Mind you, while I was in there making wires and such, I added a nice long length of wire and ring terminals (crimped, then soldered and shrink-wrapped) to both the S terminal and the battery terminal. The wires were protected with convoluted tubing, routed through the frame and away from exhaust manifold heat, and will be attached to a momentary switch mounted to the passenger-side inner fender. That will allow me to bump the engine over when performing compression tests or other diagnostic work.

Starter "S" terminal now has full power so it can engage properly.

[Schurkey]

The two wires I added to the starter solenoid--one to the "S" terminal and one to the main battery cable stud--have been routed up to the engine compartment near the coolant overflow bottle. Again, if I'd had purple wire, I'd have used it for the wiire on the "S" terminal. I didn't, so the "S" terminal wire is marked with black electrical tape.

As usual, I crimped, soldered, and shrink-wrapped ring terminals onto the wires so they could be attached to the momentary "bump" switch I'm in the process of installing. The switch came from the local NAPA as Grote #82-2151, "60 amp" rubber-covered push-button starter switch. Under $10. No mounting bracket, though. The rubber cover and bezel screws off the switch, I'll poke the switch through a hole in the mounting bracket or perhaps an existing hole in the fender assembly, and then the bezel screws on and the jam nut locks it in place.




In addition to using it to bump over the engine, the two wires are also convenient test-points for starter diagnosis. I can clip test leads from the voltmeter to the screws on the switch, and know how much voltage drop there is in the main power cable; or how much voltage is getting to the "S" terminal. I may add a third, ground wire also for starter testing. Haven't really decided on that, yet.

The switch will be cleverly hidden so that most folks would never know it's there.