I did have to activate the solenoid to get it started as it is built into the starter motor housing. The red lead is live all the way to the starter then the solenoid so they key didn’t even need to be on (or solenoid stuck shut due to damage) for it to short, it could have happened any time. I’ll give a wrecker a go thanks
then the solenoid completes the last little bit of the circuit to the motor - i meant
Jeep wanted $156 for a new one and 4 days delivery, the wreckers wanted $150 for a muddy POS corroded one 
…So I ended up repairing the harness myself, I bought a new lead and some terminal ends and took it to an auto sparky to have them crimped and soldered, he charged me $10 took him about 20 minutes. I removed all the old loom and replaced it with new loom, $4 or so. Looked pretty when it was finished anyway, about $32 I spent all up. I didn’t think to take a photo of it until after the first connection was made which was the type that required your arm rubbed in baby oil so there was no going back.
One thing that concerns me a little, I did test that starter solenoid for continuity with ground and it is completely grounded, but it still works. It must surely be using more than 15A since it blew my multi-meter so I guess I still have a problem? I’m surprised it’s even fused that high. Can someone confirm this is abnormal?
Thanks for everyones help. Glad to be back on the road for now at least!
I forgot to mention, for those interested… I found a black scorch mark on a guard panel near the starter motor, where it has a bit of an edge, so my guess is it rubbed through there initially. That red lead was burnt all the way to the end of the loom, looked like some of the loom had been on fire for a while too. Pretty lucky considering
“…I did test that starter solenoid for continuity with ground and it is completely grounded…”
The circuit is from 12V through the solenoid coil to ground, so it should show continuity to ground. The coil resistance keeps amps down to 5 or so. Will your multi-meter read 2 to 3 ohms through the solenoid coil to ground?
It is 0.6ohm on my meter, the meter reads .05ohm with the probes together. Could the coil windings have shorted but still be making enough of a field to pull the switch?
Apparently, yes. I’d be getting a new starter.
Why is there a “starter” relay in the fuse box, and a solenoid down on the starter motor? If I don’t get around to replacing the solenoid soon I assume the worst that can happen is a blown starter fuse?
Tip for finding shorts … After disconnecting the main battery, I’ve occasionally hooked up a small battery (like a 1.5 volt alkaline) and series resistor to the wire which is shorted to ground, and used a compass (the kind a boy scout would use on a hike, an east/west/north/south compass) to follow the current path. The compass is affected by the current’s magnetic field. There is an inexpensive gadget you can buy that does this same thing, only better. It doesn’t just provide a DC current, it provides a current that switches direction every second or so, that makes the compass swing back and forth.
The only reason to have a starter relay along with the starter solenoid (which is basically a relay) is when a security system is used on the vehicle or they’re trying to shunt as much current as possible around the ignition switch. The starter solenoid should only draw an amp or two though.
If the solenoid is pulling 10 amps or whatever it may be then I’d say there is an issue with the solenoid.
Some of the coil windings of the solenoid may be shorted and that is causing excessive current to flow. I suggest you compare the resistance reading to a known good solenoid.
That’s a neat idea George I’ve never thought to try that. However in this case I didn’t spend more than a few minutes looking until I found a scorched wire so it was ok.
As far as I know there is no immobiliser on the vehicle, but I could be wrong.
I had a quick look at removing that part it is difficult, drive shaft has to come out and starter and solenoid are together on same body, expensive repair for a solenoid that should be worth $5 :(.
What else can you do to prevent the problem again, the harness is still resting on the old scorch site on that little ridge and there is no holes or retainers etc to hold it off the panel. Maybe I should drill a small hole in the panel and clip a harness retainer into it?
If you can, that would be good. Or you cover it with heatshrink from Harbor Freight.
The starter solenoid (part of the starter motor) on my early 90’s Corolla draws close to 10 amps peak current. Not for very long, but for a short while during the start sequence the current draw is close to 10 amps. It doesn’t just have to pull the plunger to close the contacts, which represents a fairly big magnetic load itself, but it also has to push the gear into position to mate with the flywheel.
The starter motor itself draws close to 100 amps.
On the Corolla there is a separate starter relay under the dashboard, the purpose of that relay is to implement the clutch safety switch function.
Actually I thought it was Ford that was the king of electrical fires, esp. with ignition switches…
Glad you found the problem. If the problem was elsewhere, the vehicle (and all vehicles made in the last 30 years or so) has “fusible links” in the wiring loom that are a size or so smaller than the wiring they protect, and meant to burn up and disconnect the circuit in circumstances like this without causing further harm, but there is not one in the power feed to the starter as far as I know, so the problem really couldn’t have been anywhere else with a direct short of this magnitude. If the area around your battery terminal isn’t more than just singed, and the terminal post on the battery itself is not wobbly or loose, I’d just recharge the battery and use it. You might get it load-tested to make sure it is still putting out what it is rated for.
If the new cable is being routed across something that is likely to abrade it again, and it’s an area that doesn’t get too hot, you might try cable-tying a piece of heater hose or similar over it where it goes across that area. Surely it wasn’t designed this way, so some (poor quality) work may have been done or the original method of retaining the cable must have been lost.
George I talked to a guy about this just yesterday, he said looking at the design of the starter it looks to be the same mechanism you mentioned, on one end of the plunger pushes a lever that throws the pinion out and the other end is the switch, and he would expect it would use at least 20A. So I’m happy to leave it alone.
Oblivion the only other place this kind of short could occur is with the alternator charging lead too as far as I can tell it has no fuse either. But it would be obvious because the alternator is at the top of the engine and wires are easily followed to it.
The battery post is fine, it had a lead post mount with holes in it and a bolt held the lug onto one of those holes so I ripped one of those holes open when I bashed it, I have replaced the bolt (which was welded to its nut!) and put it through the other hole and it is all fine. The auto electrician said the same thing about the battery, if it still cranks, that is the test of whether it is good or not he wouldn’t bother replacing it if it still works. If it starts getting soft I will throw a new one in there.
As for the cable routing… There is only one way I can imagine to get the cable to the starter, given the length of the harness and the location of the last retainer before the starter - there is no other way to get it down there. The same guy I talked to suggested wrapping it in fibre glass cloth and wire tying it, which sounded like a good idea. If anyone has a jeep liberty 3.7L-V6 (03’ to 07’ I know for sure have the same loom) maybe they wouldn’t mind checking what their lead does? If you slide under the car behind the front left wheel and look straight up you’ll be staring right at it.
I put the finishing touches on it yesterday, bought some loom retainers and replaced them, so it’s back on the road with a clean bill of health (:D) Thanks everyone for their help.