More Starter Problems/Solenoid Etc

[kishy]

you don't have to change the wiring to put the newer starter in if it fits. Just connect the start wire to the fat wire. Done. That's what I did on the Mad Marquis.

You have to move the fat wire (and add the second one) so the fender-mounted relay can electrically isolate it from the thin wire, otherwise the starter can momentarily act like a generator causing the starter-mounted solenoid to remain engaged so the engine keeps spinning it for a second or two after you stop cranking.

This can cause premature starter failure.

[sly]

If the thin wire on the starter goes to the fat wire ON the starter, the fender solenoid will electrically isolate the whole thing no matter what. That's how you mount the new starter on an older car. It will NOT run for an additional 2 seconds.

[kishy]

If the thin wire on the starter goes to the fat wire ON the starter, the fender solenoid will electrically isolate the whole thing no matter what. That's how you mount the new starter on an older car. It will NOT run for an additional 2 seconds.

It isolates it from battery 12V, yes.
But it does not isolate the starter-mounted solenoid coil from the starter motor.

The motor is what generates an output voltage as the starter 'winds down' (which is a quick event).
If you have bridged the terminals at the starter like you say, then there is a path from the motor to the solenoid.

The starter itself will not run on because there is no power coming from the battery to keep it running, but the solenoid can be energized for that brief second causing the gear to remain engaged with the flywheel.

This is definitely a thing, and it definitely can happen, although it does not happen every time and some starters/their solenoids will be more or less prone to it than others.

I promise, I'm not talking out of my ass here. There's a reason why PMGR starters often come with a sheet explaining exactly this phenomenon and how important it is to avoid it.

[sly]

The one I got actually said to connect it this way if installing on a vehicle with only the fat wire to the starter. I suspect they are putting a diode to drain the voltage to prevent this.

[gadget73]

Possible, but none of this fixes Nick's problem.

https://youtu.be/cyWVPHoFGJA?t=18s

Any clue what the wiring harness in this car came from? Maybe that and some poking in Alldata can provide a clue about what the two small wires around the solenoid might be for.

[sly]

Supposedly a 92 mustang IIRC. There is great debate about that though as some bits look like it may have been a t-bird. I think only the ignition harness was used as the accessories are still panther locations. The part that boggles my mind is that removing ignition power doesn't stop it. Makes me wanna trace the trigger wire back to where it's hooked up and see if there's a relay somewhere along that line that might be sticking.

[sxcpotatoes]

Okay, updates so far. I replaced the solenoid with a Standard (chinese?/Taiwan? unit), and the positive and negative battery terminal/cables. The negative cable had the insulation brittle/flaking off when I removed it from the block and it looks green/crusty all through the inside of the braiding on the wires. I went with a 15" positive and a 40" negative terminal (pix later/some other day). Vs a 12" & 32-34?" Positive & negative cables. When I was putting it together I hadn't pushed the 90-degree studs on and the damn positive terminal rotated down while I was tightening to touch the effing "i" stud at the bottom and so when I attached the jumper cables to the battery terminals they started smoking out of the plastic rubber handle/welding the terminals.

They were hot but I got them off without burning myself, tightened things up and pressed on the studs, and it started up fine. I revved the motor some and kept it running, it came up to temp and I ran it for a half hour or longer to charge up the battery.

I will start it up daily from now on more or less, and start driving it some when I do (after I air up the tires), just to verify it's going to be dependable. I can always get it towed home if need be with AAA for now.

[sxcpotatoes]

I also went through the wiring changes stuff on the '91 (when I had my oldest nephew put it on), and he thought we had to replace the one battery terminal/clamp, but we didn't, he figured out we didn't need to redo the entire thing if you read the wiring instructions carefully.

[gadget73]

No idea if this helps any, but this is the starting circuit for a 92 Mustang and for the 82 Mark VI. Both use a red/light blue wire. No idea what red/white is, unless its faded light blue. Both indicate nothing would have gone to the I terminal from the ignition system.

Any chance this thing refuses to spit out codes, and/or has a funky idle when first started? If so I'm guessing its using the original 82 start circuit. The ECM wants to see the trans in or out of gear, and it wants to see if you are cranking the engine in order to control the idle air motor properly. If it has no idea what gear the trans is in, you won't get code output. It only knows if you are in park/neutral or not.

[sxcpotatoes]

No idea if this helps any, but this is the starting circuit for a 92 Mustang and for the 82 Mark VI. Both use a red/light blue wire. No idea what red/white is, unless its faded light blue. Both indicate nothing would have gone to the I terminal from the ignition system.

Any chance this thing refuses to spit out codes, and/or has a funky idle when first started? If so I'm guessing its using the original 82 start circuit. The ECM wants to see the trans in or out of gear, and it wants to see if you are cranking the engine in order to control the idle air motor properly. If it has no idea what gear the trans is in, you won't get code output. It only knows if you are in park/neutral or not.

YES! It sometimes has a shatty idle on startup, and you can pull codes from memory, but it's impossible to run any self-test/diagnostic like the cylinder balance or anything. John tore into the wiring harness at last ScottFest, and we connected some purple wire from/to the transmission or something underneath the car, but it didn't change anything. It got wrapped back up. I've been driving it the past couple days, just in town yesterday, and to work this morning, but it hasn't had a hint of starter trouble since I replaced the battery terminal ground to block.

I'm itching to tear into this now and correct everything, as it's 1 of 2 cars I have with working A/C. I may need to source a complete Crown Vic/GM wiring harness, and I need to trace that red/white stripe wire to see if it goes anywhere or does anything. I will take it off the 'i' terminal, because it wasn't hooked up before I tore into this and the starter was sticking. But it was on the i terminal before I tried to fix it with the glow plug relay. I still have that glow plug relay, and a blue streak (standard brand, it has longer attachment terminals, one on it now I barely get all the ring terminals and the nut on the positive battery cable attachment spot) relay is what I just took off. I may have a bunch of extra relays around now if they didn't weld themselves.

Could this wiring problem have anything to do with why the car was (and still is likely) running rich and only made 150hp on the dyno last year? Or is that unrelated?

[sly]

That could totally be related. I was also totally baffled by all the interesting idling that thing did.

[gadget73]

I wouldn't expect that to have anything to do with the fuel mix, but it will definitely make startup act stupid if the ECM doesn't know thats what you're asking it to do. The stupid idle is basically the ECM going from a state of knowing the engine isn't running to suddenly finding itself in charge of a running engine without a clue how it got to that state. Possible a fix for that would be to simply tie both of those wires together if it does currently have a working neutral safety circuit but I haven't had any coffee yet this morning so take that theory with a grain of salt.