Need help with ignition problem

[Steve Huneck]

I'm not sure if this self is inflicted or coincidence, but I’m hoping someone can help me out. First the background, I turned off the battery shutoff to change the ignition lock cylinder. When I went to switch it back on, I could not get it to turn the final click, so I removed the switch, got it working and reinstalled it. The when I went to start the car for the celebratory spin around the block it would not start. I then followed the instruction in my workshop manual (section B.3), taking a voltmeter and working forward from the battery. When I got to the coil (step g) the test to the positive side (SW) is okay, but when I test the other side (CB) I don’t get a reading. However if I remove the low-tension wire to the distributor and test on the terminal on the coil I get a reading. There are two wires coming off that terminal, the one to the distributor and, I believe, the wire running from the battery shutoff. I have since replaced the coil, but the symptoms are the same. Any ideas? Can I remove the shutoff switch from the equation, by directly grounding the coil?

 

[Dave Russell]

First the ignition circuit. When you turn on the ignition switch there is 12 volts on the coil SW side. The CB side of the coil is connected to the distributor points. The points opening & closing is what causes the coil to fire.

There is a contact in the battery shutoff switch that is supposed to ground the points side of the coil when the battery switch is off. (Anti theft protection) Something is screwed up inside the switch.

If you directly ground the coil it will bypass the points & it still won't work.

Just disconnect the WH/BK wire on the points (CB) side of the coil that goes back to the battery switch. The wire that doesn't go to the distributor. Leave the WH/BK wire that goes to the distributor in place.

This will get things going until you can repair, replace, or eliminate the cutoff switch. Some folks just leave this grounding wire disconnected permanently. One less place for something to go wrong.

If the cutoff switch main contacts completely fail you will have a poor or no ground path for the battery & the starter will not crank. You can bypass it by connecting both heavy wires on it to a single terminal.
D

[ 04-22-2004: Message edited by: Dave Russell ]</p>

 

[piman]

Hello Steve,
just remember when you do a voltage check of the coil terminals, when the points are closed you will get virtually zero on the distributor connected side of the coil, typically 0.2 volts.
This is without the connection to the Battery Isolation switch. Just take off the distributor cap to check and if the points are closed either turn the engine a bit or flick them open with a small screwdriver. Incidentally the voltage across the closed points is a good check of their condition and that of all the connections between the coil and the distributor.

Alec

 

[Dave Russell]

Alec is absolutely correct. He usually is. With the WH/BK wire that goes to the cutoff switch removed from the CB terminal of the coil, there should be 12 volts on that terminal when the points are open & nearly zero when the points are closed.

If this is the case, & reconnecting the other WH/BK wire from the battery switch causes zero volts when the points are open, the problem is in the battery switch not ungrounding the coil wire.

If the voltage on the CB terminal is not 12 volts with the points open, there is a ground in the wire going to the points, the points are not opening, or there is a ground on the hot side of the points. Just as Alec says.

It IS possible that the situation is coincidental & there is NO problem with the battery switch.
D

 

[Steve Huneck]

Thanks a lot! you guys are great, now if I can just find a way to sneak out of work and get home to try your suggestions. Do Healey owners get special work privlages?