No Spark and Stumped!

[Mike V. Florida]

This is my generic no spark troubleshooting list,

No Spark
Some possibilities are:
1.Blown or defective fuse (use of a fuse is an aftermarket item)
2.Bad connections at ammeter, or ammeter itself (t0 find out put a jumper wire from one post of the terminal box to the other to take the ammeter out of the circuit temporarily)
3.Bad ignition switch and/or cable, or loose cable connection at switch.
4.Loose or broken wires at bottom of coil
5.Loose or broken wires inside terminal box
6.Loose, bare or broken pigtail wire under distributor plate, or wire grounding to plate or distributor body
7.Points not opening, or point arm grounding to cam due to worn rubbing block
8.Worn electrode in underside of distributor cap
9.Loose or broken high tension wire from coil to cap
10.Condenser burned out or grounding (some condensers are too long and can touch the distributor body inside)
11.Weak coil
12.Rotor not turning due to loose cam screw or bad timing gear.


Ok now break out a volt meter (a light bulb can give false readings).
Start at the fuse block, you should have voltage on both sides of the fuse. If you only have voltage on one side, replace the fuse or fuse block.

Now with voltage on both sides of the fuse, move up to the junction box. There should be voltage at both terminals. If voltage is present only on one side the problem is at the ampmeter and you should Jumper the ampmeter for now.
You should have voltage on both sides of the coil. If not,
remove the red wire on the coil and check again. If you now have voltage on both sides, you have a problem further on. If the voltage is still only in one side you have a bad coil.

Open the points with a piece of paper and remove the condenser. Turn the key on and you should have voltage at the points.
Replace the condenser and you should still have voltage.

If voltage is missing, remove the top plate and check for voltage on the bottom plate.

Check is the connector from the ignition switch screwed in to far? Do you have voltage on the wire to the upper plate?

Is this wire shorting to ground or broken?

Remove the paper from the points and see that the points are closed. You should not have 0 volts at the points. If not,
The points are dirty or the distributor is not grounded well to the engine.

[d.j. moordigian]

Originally Posted by Purdy Swoft

The condenser may not be grounding to the distributor housing check the screw on the right side where the condenser connects to the housing for tightness. too much paint on the housing could effect ground. The tab on the lower plate may be grounding to the housing on the left side of the distributor where the condenser connects to the lower plate. There should be a fiber washer glued to the outside of the tab on the lower plate where the condenser connects to the lower plate. The glued fiber washer prevents the lower plate connection to the condenser from shorting to the housing of the distributor.

Why does the condenser need to be grounded? No current runs threw it,..
..correct?

[Lena's Dad]

Mike V.
Thanks for your very detailed check list. I'm bookmarking that one.
Lena and I both appreciate it!

[Mike V. Florida]

Originally Posted by d.j. moordigian

Why does the condenser need to be grounded? No current runs threw it,..
..correct?

The Condenser "absorbs" electricity and gives it back to the ignition system like a rechargeable battery. You cannot recharge a battery with one wire from the charger attached.

[Purdy Swoft]

Originally Posted by d.j. moordigian

Why does the condenser need to be grounded? No current runs threw it,..
..correct?

I can't explain it but i've found it to be true that if the screw gets loose or the tab comes unsoldered . A lot of the older condensers had the tab soldered in place. When heat from the manifold melted the solder, the condenser then lost ground and quit working. If you don't believe it try loosening or removing the condenser mounting screw on your model A to prove it. insert smiley face. The condenser can be charged through one wire by a person holding the condenser in his hand. If the wire end is touched to another person that is grounded it will shock them. If the person isn't grounded, they won't get shocked.

[d.j. moordigian]

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Originally Posted by Purdy Swoft

I can't explain it but i've found it to be true that if the screw gets loose or the tab comes unsoldered . A lot of the older condensers had the tab soldered in place. When heat from the manifold melted the solder, the condenser then lost ground and quit working. If you don't believe it try loosening or removing the condenser mounting screw on your model A to prove it. insert smiley face. The condenser can be charged through one wire by a person holding the condenser in his hand. If the wire end is touched to another person that is grounded it will shock them. If the person isn't grounded, they won't get shocked.

I still do quite a lot of Distributors here at work. I have a Sun machine.
I've even run them, on the machine, with no condenser. I know how it
works and why(I think) it's there. I just never thought about it being
grounded!
As far as loading condensers,....ya, I still do that.