Starter Solenoid?

[blu60]

Good day all

My SIII has recently begun acting funny when I start it. Here's the symptom and tell me what you think I should test.

When starting the engine - key in starting position starter spins nicely, the engine only gets spark when I put the key from "start" to "on", she fires right up smooth idle and plenty of power.

I have removed points and added Pertronix years ago, recent Lucas coil, replaced ignition switch which made no difference.

thanks for any ideas

Herman
1973 88 NADA

[SafeAirOne]

If power is going to the coil only when the key is in the run position, and not in the start position, I'd suspect the ignition switch. The solenoid has nothing to do with the coil circuit.

[siii8873]

have someone check for voltage at the coil when switch is in start position. that will test the switch which it does sound like.

[blu60]

Agreed that it does appear like an ignition switch problem, but as I mentioned in the original post, I did replace it and it made no difference. Any ideas always welcome.

Thank you and hope all have a great week.

[SafeAirOne]

Agreed that it does appear like an ignition switch problem, but as I mentioned in the original post, I did replace it and it made no difference. Any ideas always welcome.

Thank you and hope all have a great week.

Oops...Ok--didn't get that at all from the original post...Make sure the white wire is on the ignition switch terminal that is hot in both run AND start. Not all of the terminals are like that and often the markings on the back of the switch have no resemblance to the markings on the schematic.

Do the oil pressure, charge light and choke light also stop working in the start position?

[blu60]

charge light, etc operate in "on" and "start"

[SafeAirOne]

charge light, etc operate in "on" and "start"

That's not helping my theory at all.

If the wiring hasn't been altered, then this means the coil should also be getting power when the key is in the start position. Like Bob says, check to see what you're getting for voltage at the + terminal at the coil with the key in the on position and also the start position.

If the voltage is really low when in the start position, try disconnecting the white/red wire from the solenoid on the starter (this will disable the starter) and try the test again and see if the voltage number is better on the + coil terminal with the key in the start position. Make sure you position that loose red/white wire so that it won't contact any metal part of the vehicle when you turn the key to the start position.

If the voltage on the + coil terminal has vastly improved with the white/red wire disconnected from the starter, I'd start looking for issues that would sap power to other systems when there's a high-draw event (like starting) occurring. Things like:

• Battery condition--battery must be able to supply other systems at the same time as a high-draw systems are operating.
• Starter condition--A malfunctioning or restrained starter motor will draw a lot more electricity than a properly operating one
• Ground connections--Poor ground connections between the negative battery cable and the chassis and engine, poor starter-to-engine ground or poor distributor-to-engine ground could cause the symptoms.
• Poor contact between the white wire to the coil and it's spade terminal behind the fuse panel could cause the coil to lose power during high-draw operations while the charge and oil pressure lamps remain brightly lit (they are connected to separate spade terminals on the same circuit behind the fuse panel).

Those are probably things that I'd be first thinking about if I were experiencing the symptoms you describe. Don't forget to re-connect the white/red wire to the starter solenoid.

[antichrist]

To see if it's the high draw issue, disconnect the cable that runs from the solenoid to the starter, turn the ignition to 'start' and see if you have 12v at the coil.
(oops, variation on Mark's suggestion)

When checking the starter connections, don't focus only on the earth cables.
This is the positive cable from my wife's disco when we bought it (second one is 6" from the clamp)

[SafeAirOne]

When checking the starter connections, don't focus only on the earth cables.

Good Point. Electricity that can't get out is just as bad as electricity that can't get back.

[blu60]

OK voltage at coil key in "on" position 11.4 V
key in start 9.4 V

what does this tell me?

thanks!

[SafeAirOne]

OK voltage at coil key in "on" position 11.4 V
key in start 9.4 V

what does this tell me?

thanks!

It tells you your battery is essentially dead.

[blu60]

all is working fine, just charged the battery - FULLY

Thanks for all the responses.

[antichrist]

So now you need to find out why your battery wasn't fully charged?
What's the voltage at the battery with the engine running? Should be 14+ volts with the accessories all on.
If not, and I'm guessing not, look at all your connections for soundness. Then get the alternator and battery tested.