No Spark

[Mac]

My 1970 GT has been laid up for a couple of years because of a cracked head. My son was working on it but lost interest and I ended up putting it back together. I'm trying to fire it off, but can't seem to get a spark. It's wired per the attached. I've traced and replaced all the wires except the black/red off the starter and the negative green on the ignition coil. I also put a new ignition coil in. I tried to check for spark by running a wire from the positive battery terminal to the positive on the coil and holding the coil center wire near the engine block while my wife hit the pushbutton switch. Still, I can't seem to get a spark.

I'm a chemical engineer, not an electrical one. Can anyone suggest how I might troubleshoot the problem? Thanks

[wrench459]

Have you checked the point gap? Should be around .016. the rubbing block wears changing the gap.
If you hot wire the coil and remove the neg. side wires then place a jumper wire and tap it to ground you should get spark.

[namba209]

Mac, noted you didn't trace the green wires (2) at the coil negative. One goes to the tach, the other to the points under the distributor cap, where the condensor pigtail attaches. The black wire on the vertical spade lug at the solenoid goes to the coil positive post as does a "transparent" resistor wire from the fuse block. If you have the "resistor" wire, you do not need a ballast resistor in the coil circuit. If you hooked up the coil negative wire to the condensor body, you won't get a spark, because you've grounded the coil through it and not the points, which need to open and close the circuit to the coil for charging and dumping the spark to the plugs. It may be an idea to check to gap on the points, if they don't open to .018", you'll get no spark or weak spark. HTH.

[Dennis Texas]

try sanding the surface of points down the surface may be coated with crud from sitting that long and not making good contact.

[Mac]

So I just tried the following:
1. Removed the green and condenser wires from the ignition coil.
2. Ran a wire from the positive side of the battery to the positive on the ignition coil.
3. Held the center wire from the coil against the block.
4. Had my wife hit the pushbutton switch.

Still no spark from the center wire. I tried it with just the condenser wire off and the green wire on and the same thing happened.

Am I going about it wrong? If not what can I check next. thanks

[wrench459]

no ground for the primary.
Got a test light? If you do hook all wires back up (stock)
place the test light on the neg side of the coil and spin it over.. it should blink,pulse

[trlmr]

I agree with dennis texas, after sitting that long points will corrode or get moisture in them. That is the first place I would look.

[namba209]

Mac, you need the negative side of the coil to go to the points. The opening and closing of the points is what charges the coil for spark discharge. As others have said, check the points for the correct gap and the points contacts themselves for pitting. You may have to replace them if they are pitted.

[Mac]

My attached electrical diagram was wrong, the negative off the coil “is” going to the points. I just put new points in and gapped them. So all told I have a new coil, points, condenser, rotor, cap, and pretty new spark plug wires. The engine cranks fine, but I still don’t get any spark off the coil center wire when I hold it to the block, even when I try a jumper wire. Any other ideas, its got to be something simple?

[Dennis Texas]

inside the distributor under the points there is a gounding wire mesh looking, and a ball bearing I believe, make sure it is clean and intact thats were the points gets it ground from the engine. If nothing else take a jumper from the battery negative to the side of the coil were the points hooks to that would bypass points and any grounding issues and just briefly touch the terminal work back from there.If it doesn't spark now then you either don't have positive 12 volts on the other side of the coil or the coil is bad.

[kwilford]

This might be a dumb question, but when you are cranking it, is there 12 volts at the +'ve side of the coil? In your diagram you are using a push button starter to energize the solenoid, which "should" send power to the coil via the "start" wire from the solenoid. For that matter, is there power to the coil when the ignition is turned on?

Put a voltmeter (or test light) on the +'ve side of the coil when you're cranking it. Now do the same on the negative side. The +'ve side should be a steady +/- 12 volts, while the -'ve side should bounce between somewhat less than 12 volts and zero (as the points open and close). If there is power to the +'ve side, and the points are grounding the -ve side as they close, and you STILL have no spark, then the coil is shot.

[Mac]

1. I did what DTexas suggested (jumped to the battery negative from the ignition coil). This energized the test light I had on the positive resistor wire coming into the coil. In addition, when I cracked it I got a spark on the block.

2. When I I have no wire jumps in the circuit, the test light does not come on on either the positive or negative side when I cranck (as suggested by kwilford).

3. If I jump a positive from the battery to the coil and leave everything else the same, I still do not get a light on either the positive or the negative.

Does the fact that I get a spark when jumping the negative, as described in item 1 above, indicate that eveything coming into the positive onfthe coil is okay and its most likely something in the distributor. I looked for the grounding mesh and bearing as suggested by DTexas but do not see anything amiss. Do I need to remove the points to see them?

My son had the distributor out while we were changing the head. Since it has new points (with gap reset), condenser, rotor, & cap, is there something else that could be screwed up? Should I out the distributor and have someone look at it?

Sorry for the stupid questions. You guys are helping immensley. It was sort of exiting getting at least some kind of a spark.

[Dennis Texas]

It appears you have some sort of problem with the distributor The negative (ground) side of the battery is not making it through the points? Have you checked with the condenser not attached (condenser may be shorted) and did you check under the points for the ground cable inside the distributor. The points are pretty straight forward just insure the wires going to the points and condenser are not grounded, the coil has to see the contacts open and close to pass high voltage spark.

[wayne70gt]

Read through this thread quick and have one thought. I see that it has not been run for some time and you are using a pushbutton to start. This seems simple but, is the ignition switch in the run position and if so, could the switch itself be bad. I am not sure how these are wired, maybe it won't crank unless the switch is on. jmtcw

Wayne

[BQS4]

Wayne;
I was thinking the same thing, just wanted to see if it was something else. The "older guys" will remember that you used to have to start cars by turning on the key, then stepping on the starter.

[namba209]

Originally Posted by BQS4 The "older guys" will remember that you used to have to start cars by turning on the key, then stepping on the starter.

O.K. Gene, I represent that, and yes I did have a car with a step on starter.

Back to the case at hand. The condensor has to be grounded to the body of the distributor, and the dissy grounds through the clamp hold down bolt. Make sure it's all nice, clean and tight. I have seen new condensors go bad out of the box. So, for me if it ain't broke don't fix/change it. There's no moving parts in them, they either work or they don't. I noted a test lamp was used, how about putting it on each side of the points, that way when the points are closed the lite should be out, when they are open, the lite should be on. That will tell if there is a ground through the points, like there should be. With the key in the on position, of course. HTH.

[kwilford]

Originally Posted by Mac 1. I did what DTexas suggested (jumped to the battery negative from the ignition coil). This energized the test light I had on the positive resistor wire coming into the coil. In addition, when I cracked it I got a spark on the block..

A BUNCH of questions:
What side of the coil did you "jump" to the battery negative?
And was it the battery negative, or the positive?
Was it the same side that the test light was hooked to or the opposite terminal?
What do you mean "cracked it"? If you put 12 volts to the +'ve side of the coil, and ground the negative, you just simulated what the points do, and the coil will create a spark. And will every time you ground the -'ve terminal, just like the points.

This is rather confusing, as the +'ve side of the coil MUST have 12 volts to it whenever the ignition is on, or we are wasting our time here. If it does, your test light (which has one side grounded, right?) should light up by doing nothing other than turning the ignition on. If doesn't happen, find out why NOW and quit mucking around with the points and coil until you fix that.

Originally Posted by Mac 2. When I I have no wire jumps in the circuit, the test light does not come on on either the positive or negative side when I cranck (as suggested by kwilford)..

OK, I think you're wasting your time until you can find out why there isn't power to the coil.

Originally Posted by Mac 3. If I jump a positive from the battery to the coil and leave everything else the same, I still do not get a light on either the positive or the negative..

I don't think that is possible. If you put 12 volts to the +'ve terminal, then you have 12 volts. If the -'ve side is grounded (eg through the points being closed), then the voltage will drop, as you are shorting out the coil, and there will be current flow through the coil. But you will still have whatever voltage you appllied less the voltage drop due to the current draw.

Originally Posted by Mac Does the fact that I get a spark when jumping the negative, as described in item 1 above, indicate that eveything coming into the positive onfthe coil is okay and its most likely something in the distributor. I looked for the grounding mesh and bearing as suggested by DTexas but do not see anything amiss. Do I need to remove the points to see them?.

When you get power to the +ve side of the coil, and the points properly close (and are grounded), then you willll get spark.

Originally Posted by Mac My son had the distributor out while we were changing the head. Since it has new points (with gap reset), condenser, rotor, & cap, is there something else that could be screwed up? Should I out the distributor and have someone look at it?.

Maybe, the most common problem is the little grounding strap inside the distributor on the advance plate gets broken lose, and therefor the points don't actually ground the -ve side of the coil

Originally Posted by Mac Sorry for the stupid questions. You guys are helping immensley. It was sort of exiting getting at least some kind of a spark.

This might be more exiting, I mean exciting, if you have power to the coil when you turn on the ignition, and then grab the high tension lead

[Mac]

After looking at my parts car, I can see where the grounding mesh wire is supposed to be.

I think I may have stumbled upon a likely scenario. My son is very anal when he works on something. When he removed the distributor he cleaned the inside spotless. My guess is while doing so he broke the mesh loose and never got around to putting it back on. Then when I put the distributor in the car, I didn't notice it was missing. He can't remember, but admits it might have happened that way.

I'm done messing with it for the weekend, but this strap thing seems like a likely culprit to fix next weekend. Thanks

[wrench459]

A simple voltage drop test will tell the story.
Test lights will get you into trouble..but there a handy tool.
With the key on(B+ side of the coil hot) points closed hook the clamp of the test light on the neg. battery terminal then place the probe on any part of the dissy housing.
The light better not glow bright or you got a bad ground.
The preferred method requires a voltmeter with the same hook up.
Any reading over .5 volts = bad ground.
Then start back tracking till the light go out or the meter goes low. The problem will be inbetween the two points.
Sounds like your on the right track..the strap from the breaker plate to housing is there for a reason.

[Dennis Texas]

Originally Posted by Mac After looking at my parts car, I can see where the grounding mesh wire is supposed to be. My guess is while doing so he broke the mesh loose and never got around to putting it back on. Then when I put the distributor in the car, I didn't notice it was missing. He can't remember, but admits it might have happened that way.

replace the ground wire and think your fixed. If still have trouble then points are not opening or you have a short in wiring in the points area.