Starter motor wiring

[mgaut]

Hi

I hope someone can help.

I've got a mini for circuit racing for one of the kids, and whilst out having some driving lessons in a local field at the weekend the starter motor has stopped working.

The battery cable connects direct to one side of the starter, and a second wire runs from a push start in the car onto a large connector. There is 12v on the push start cable when it is not connected to the starter, but nothing when connected.

There is no earth cable anywhere on the starter motor.

I can't help but thinking that there should be an earth cable somewhere. I've tried 2 other starter motors, but they all have the same symptoms.

Can someone put me out of my misery and give me a simple explanation as to whether we've lost any wires. There is a cable from the solenoid to the starter.

As a last resort we can bump start it, but that's hard work !!

Apologies if I don't repond swiftly; I'm working away for the next 3 days.

Many thanks on behalf of a frustrated 12 year old !!

Mike

[allgearnoidea]

hey, is the starter a pre engaged (piggy back) or inertia type? does the starter click like its a solenoid problem? I had this problem, firstly I tried changing starter, that didn’t work so then I tried increasing the size of the wire from the ignition barrel to the large spade connector on the solenoid (white, red trace??) which seems to have done the trick. (my car was converted from inertia to pre engaged so the wiring was non standard!) Hope this helps a little?? oh and i belive the starter is earthed from where it bolts on through the engine.

Edited by allgearnoidea on Monday 14th June 21:30

[jhfozzy]

If you've got 12v at the solenoid cable when disconnected, but 0v when connected, it sounds like a problem with a bad connection before the starter.

I would try the voltage at the switch whilst the cable was connected to the starter. If you get a steady 12v at the switch when pressed then the problem lies between the switch and the starter. If you get 12v here and then 0v when the switch is pressed, then the fault is in the switch or further up the loom.

[mgaut]

many thanks for the replies.

Based on what you've said (and having replaced the wire from starter button to starter motor) I'm leaning towards a faulty starter button, so will try and get to Maplins/wherever later but away from the car until the weekend now.

Is it only one permanent live and one "switched" live that is required ?? No idea what sort of starter it is; basic/original I'd suggest.

cheers

Mike

[jhfozzy]

mgaut said:

many thanks for the replies.

Based on what you've said (and having replaced the wire from starter button to starter motor) I'm leaning towards a faulty starter button, so will try and get to Maplins/wherever later but away from the car until the weekend now.

Is it only one permanent live and one "switched" live that is required ?? No idea what sort of starter it is; basic/original I'd suggest.

cheers

Mike

Sorry for the late reply.

Most normal starters use just one heavy cable straight from the battery and one lighter cable from the switch.

If you can get to the starter terminals easily enough, I'd temporarily attach a long wire to the lighter of the two terminals and run it up to the starter switch. Making sure it's out of gear, touch the wire to the starter side of the switch and press the button. If nothing happens, touch the wire to the live side of the switch if the starter engages, the switch is goosed, if nothing still happens, the fault is further up the circuit. Follow the existing wire up and keep testing with your wire until you locate the fault.

HTH,

John.

[cpas]

Firstly, make sure he earth from the engine to the body is OK and the earth from the battery to the body. Also check the positive connectors to the battery etc. The starter draws much more current than anything else so will easily show up any faults.

Also, the starter circuit has a primary high powered circuit and a secondary lower powered circuit (both 12V) and works as follows. The power from the battery goes via a heavy duty cable into the solonoid (electric switch) in the engine bay. Another heavy duty cable goes from another terminal on the solonoid to the starter motor. The return from the starter is via the engine and earth straps. When you move the ignition key to the 'start' position, power from the key travels along a lower power circuit to the solonoid, activating the electric switch (like a relay) which completes the heavy duty circuit to the starter motor. The lower powered circuit must also be earthed well. This system prevents the huge power to the starter having to travel through the ignition switch and is the basis for the starting system on all cars.

Hope this helps?!

[mgaut]

All

many thanks to everyone for the suggestions.

I've replaced the switch and starter button, the 3 wires from them to the starter & coil, and the battery terminals, and BINGO !! We're up and running.

much appreciated

Mike