Is this a bad starter, solenoid, cable or key switch?

oz · Aug 30, 2004

I have this nagging problem with my Mustang that I need some help with...

When I turn the key to start it sometimes pauses before the starter kicks in. Last night I heard a click under hood (from the solenoid?) but the starter didn't turn. The key had been on for about 10 minutes prior to attempting to start the engine (I was actually in the process of troubleshooting some other problems).

I put a charger on the battery (turned to '100A start') and tried to start it. Still nothing. After 3 or 4 tries, the engine fired up like nothing was wrong.
I know you're going to ask if there was draw on the battery and I can't tell you (I didn't look at the ammeter). The battery is fairly fresh and had more than 12V when this happened. This problem occurs intermittently and does not seem to get worse with heat (like a bad cable). Most times I do not hear a click from the solenoid when this happens. I turn the key and nothing happens usually (no clicks or anything) or there is a quiet pause and then the starter/engine fires up.

Could this be a key switch problem too?

I would like to avoid replacing the solenoid, cable, switch and starter if possible but will have to, one at a time if nobody can give me a suggestion.

THANKS!!!

pa0101 · Aug 30, 2004

Some troubleshooting is required. Get a meter (better) or 12v test light. When the problem happens pop the hood, leave the ignition off (so the engine cannot start).

BE SURE THE CAR IS IN NEUTRAL. STAND TO THE SIDE, NOT IN FRONT OF, THE CAR!!! READ AND UNDERSTAND THESE DIRECTIONS - DO NOT SHORT +12v TO GROUND AT ANY TIME!

At the starter relay behind the battery short between the +12v battery terminal cable connection at the relay and the "S" terminal. This should make the starter turn. If it does, suspect the ignition switch/wires.

If it does not measure 12v to ground at the starter relay input. If no voltage, or if voltage drops off when you try to start, suspect the battery or cable. If input is OK, then measure 12v to ground at the starter relay output (large cable to starter) while shorting battery terminal to "S" to activate relay.

If voltage is there, suspect the starter or switch/starter cable. To detect, measure at starter. You probably get the idea.

While you're at it, look for corrosion/loose connections, and take care of those. Don't forget the connection of the starter relay itself to ground - this is only through screws into the body, and seems to me a bit weak, so you could always add another ground wire.

oz · Aug 30, 2004

Excellent response... I can do that...

I made a couple of voltage readings with the key on, engine off yesterday before I encountered this problem (again).

The battery was 11.96 V
bat '-' to solenoid bat terminal:11.94 V
bat '-' to S terminal: 0
bat '-' to I terminal: 9.7 V
bat '-' to coil '+': 11.28 V (I spliced around the ballast wire so my Pertronix Flamethrower coil would see full voltage). Not sure why this is not quite full voltage...?

Where does the wire on the S and I terminals go? Since I have a Pertronix with low resistance coil, I need full voltage to the coil. I think I have achieved this by splicing around the ballast for 'run' but where does the voltage to the coil come from for 'start'?

Yea, I should have probably checked all these to ground instead of the battery '-'...

THANKS!!!

WORTH · Aug 30, 2004

during crank you get a full battery voltage from the I terminal on the solinoid.

the s terminal is the one that gets 12v to start from the ignition switch.

pa0101 · Aug 30, 2004

... so the "I" terminal makes the spark hotter, bypasses the ballast resistor. If you've already bypassed it for Pertronix then it's a "no care" ... it's not involved in cranking anyway, just ignition

... the voltage with key on, engine off seemed a bit low at 11.96v. Either you've got a battery that's starting to go (one bad cell) or a bad meter ... if you have access to another car, compare readings ... maybe stop by a parts shop and ask them to do a load test on your battery if its old enough to be a suspect ... see http://www.exide.com/products/trans/na/battery_care/checking_battery_condition.pdf for a good chart on voltage/state of charge

... otherwise the troubleshooting as above will lead you to what's wrong

oz · Aug 31, 2004

Figured it out

Thanks for the replies... The battery was new last year but has sat around while I rebuilt the engine, etc. It does seem a little low but considering I keep starting the car, looking for another problem (low vacuum at idle - another thread...) and shutting it off, it is not surprising that the battery would be a little low...

pa0101,
The starter is the problem. I followed your proceedure to the letter and managed to check the voltages as I jumpered the 'S' terminal and the starter is seeing full voltage but won't turn over when it gets warm (I assume turning the key repeatedly with the draw on the battery doesn't help the voltage situation). I have found that I can get the car started when cold but the starter won't function after it's warm. Bought a rebuilt one at NPD (and a cable at a discount auto parts store for good measure).

...now if you have any ideas about my low vacuum situation please take a look at my other recent thread....

THANKS!!!!

Is this a bad starter, solenoid, cable or key switch?

oz

pa0101

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oz

WORTH

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