Starter shorting/cooking wires

[leeandoona]

So. My minor which has sat idle for many many many months wouldn’t start or even turn. It’s a 58 and has a pull starter. When pulling the starter knob the dash lights dim. I checked the power to the starter motor and sure enough there was no power reaching it. I bridged the connection on the switch but this did nothing and did a volt meter test and no power was jumping from one side to the other unless bridged. I tested the starter independently and discovered it too was not working so removed it, bench tested and sure enough it was dead.
During all this I noted the wires were getting very hot when attempting to start/power the starter.
So I checked and cleaned all the earths, including the gearbox earth strap. Bought a new starter which I bench tested and confirmed was operating. Fitted the starter, pulled the starter knob and the starter span once and then after an audiable bang, it stopped working and returned to hot wires and dimming cabin lihjts.
Checked fuses, checked earths again. All lights operate as expected so appears to be electrically okay on that side of things. Removed new starter to discover it too is now dead. So it’s cooking starter motors. I’m assuming this is a short?
I’ve bought a new starter switch/solenoid (I know it’s not really a solenoid).
Anyone had this happen? I don’t really want to fit another starter and Jill that too!

[oliver90owner]

First thing - can you confirm that the engine actually turns?

Further response after that.

[StillGotMy1stCar]

Is the engine seized overloading the stalled starter motor. Can you turn the engine with the starting handle, fan or rocking in gear.

Regards John

[leeandoona]

Engine turns freely. Yes. Not seized and I e turned it over using the starting handle.

[oliver90owner]

Was the replacement starter motor a secondhand purchase or bought from a reputable source of refurbished starter motors.?

If the latter, I would think they should replace the unit. I cannot understand how the starter should fail so quickly. The loud bang would indicate something is shorting inside the starter motor. I’m assuming, here, that you did not engage the power for too long.

[leeandoona]

Brand new from reputable minor specialist. No, it was literally one pull on the starter and a brief spin over of the engine, then bang and failure.

Wires from starter and to battery very hot. Can’t see any obvious signs of bad earth, all earth points nice and
Clean and when checked for continuity they show appear normal.

I’m assuming there is a short somewhere?

[oliver90owner]

Yes, there is definitely a short circuit somewhere. The starter motor windings should show a very low resistance, so not easily checked for true answer with a cheap multimeter. It would draw upwards of 200A at zero speed, so resistance of around 0.05 Ohms, and 60-70A when up to speed (impedance, rather than resistance while running).

Talk to your supplier is my advice.

As a further check is there a short circuit when operating the starter switch while the starter motor is disconnected? That should then be an open circuit (so no light dimming, etc).

[geoberni]

Something is certainly not right, that's for certain.

Was the bang from the starter?
Did you go inside to pull the knob, or push the central button on the switch under the bonnet?

As Oliver asked, with the cable disconnected from the Starter Motor, and the end insulated from touching anything , what if anything happens when you operate the Start Switch?
There should be nothing at all happening.

I can't see a way for 'the car' to make the Starter go 'Bang'.....especially since you say the engine will rotate on the handle...
It's pointing to a faulty Starter, but what's the odds of a replacement having the same fault as the original... Not really likely.

I think you need someone with basic electrical knowledge/competence to come and look at it.
Remote diagnosis is not really practical; there's very likely something going on that you're not thinking to tell us about, you may not even be aware of it (whatever it is).
Those supply cables getting hot can only indicate a massive 'dead short'; they should take 200 amps or so for several seconds before even warming up. If you keep playing with it you're risking damage to the battery.

Can you post photos of the installation, showing the Starter Sw and the Starter, including all connections to them.??