Crank no spark. 1974 302 with points.

[Heus33]

I can’t figure this out.
I have spark coming out of the coil, but no spark at any of the spark plugs.

I have tried the old cap and rotor with the old points. I have tried new cap and rotor with new points. And the old cap and rotor with the new points. I have set the point gap, still no spark out of the cap. I’m sure I’m missing something simple, what can I be overlooking?


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[serial car restorer]

How are you determining spark at the coil but not at the plugs? Timing light? Or..?

 

[Heus33]

How are you determining spark at the coil but not at the plugs? Timing light? Or..?

I pulled the coil wire and watched it jump spark to the block while cranking.


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[serial car restorer]

And so doing the same at a plug does not spark? If so, the points are fine since that is what triggers the coil to fire. But the spark isn't getting distributed correctly. Bad cap or rotor seems unlikely, since you have tried more than one set. That leaves bad wires, of maybe way out of time. Or maybe not getting the cap seated all the way?

 

[Heus33]

And so doing the same at a plug does not spark? If so, the points are fine since that is what triggers the coil to fire. But the spark isn't getting distributed correctly. Bad cap or rotor seems unlikely, since you have tried more than one set. That leaves bad wires, of maybe way out of time. Or maybe not getting the cap seated all the way?

I haven’t replaced all of the wires. I could try that next.
I thought about not having the cap seated all the way or the wire on the cap properly. Is there any good way to test that?
I can just push them down as far as they’ll go


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[73azbronco]

Little more background, new to you truck? Old one doing tuneup? It ran before, it didnt run?

so you are testing the wire on a plug this is laying on block, not in the plug hole? spark plug gap?

i agree if you are getting coil spark, points and dwell are in the ballpark.

how old are the wires? More than a few, full tune up is usually new wires included.

If the cap latches snap on, it's as on as it gets.

How old is cap?

 

[Heus33]

Little more background, new to you truck? Old one doing tuneup? It ran before, it didnt run?

so you are testing the wire on a plug this is laying on block, not in the plug hole? spark plug gap?

i agree if you are getting coil spark, points and dwell are in the ballpark.

how old are the wires? More than a few, full tune up is usually new wires included.

If the cap latches snap on, it's as on as it gets.

How old is cap?

New to me
Ran before, but this was a few years ago
I tested the plug coming out of the coil that would go into the distributor for spark. I’m not getting any spark out of the cap to the spark plugs.
The old cap is an unknown age. I do have a new cap that I’ve tried as well. With the same result.

The only thing I haven’t replaced are the rest of the spark plug wires, which I suppose is next on the list!


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[blade]

Test all of your wires. Make sure the coil to cap wire is good.

 

[73azbronco]

does the cap match the rotor style?

 

[Oldtimer]

Post part numbers of new cap, and rotor.

 

[Heus33]

Thanks for all the advice guys. I’ll post those pictures and part numbers on Monday when I’m back at my shop.


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[NGABronco]

New Condenser with the points???

 

[Broncobowsher]

I have been bite by a bad coil wire (coil to distributor) more than once.

 

[m_m70]

does the cap match the rotor style?

where I would look

 

[DirtDonk]

Make sure that the rotor is turning consistently.
Yes, for you to even have spark at the coil, the distributor shaft has to be turning at least a little.
But you might as well check to be certain.

Someone mentioned timing already, but you definitely need to verify that. If the rotor is far enough out of phase, spark, might be jumping inside the cap, but not getting to the terminals.
This is also pretty unlikely, but it needs to be confirmed.

And just to be sure here, when you jump the coil wire to ground and you see a spark, just how strong is it? Is it good strong, fat, yellow/white spark? Or is it sort of anemic looking blue, or light yellow orange Spark?
Do you hear a really good snap when it jumps the gap?

If you do have a timing light, use it for this testing. It’s the easiest way to confirm spark is passing through the wires.
Any time the spark is present you should see a flash of the light.
And you don’t have to take the time and trouble to pull a wire and find a good grounding point.

And doing this will ultimately improve the life of the wires. Less likely to pull an end off, the fewer times you have to pull the wire off of either the distributor cap or a plug.

 

[DirtDonk]

Also, next time you have the cap off and you’re cranking the engine to check the rotor rotation, see if there is a lot of sparkage at the point gap.
There’s always a little bit, but if you see a lot of spark dancing around the points, that usually points to what was mentioned earlier. A bad condenser.
A problem that is far to common these days.

 

[EPB72]

When your checking coil output how far of a gap are you creating I would expect an inch to inch and a quarter with consistent spark cranking ,,, if you check with a small gap your coil output could still be low,,