No spark

Rich77 said:

Hello,
My truck is a ‘77 c10 with 400/th350.

The engine is rebuilt. Basically everything under the hood is brand new.
First time trying to fire up the engine-
Fill carb bowls, turn key, there was a “pop!” and just turn over without firing.
I thought that maybe the timing was off. Went through the whole process with the distributor again and made sure that it was correct.
I tried firing it up again, and it will only turn over but not fire.
I pulled number one spark plug and checked it on a valve cover, and it does not spark.
I’m using the Summit Racing Ready-to-Run Billet Distributors SUM-850205 with mds 8207 SS coil.
Do I need to jumper some ignition terminals?

Thanks!

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Do you have the original distributor? I would say try that..

Have you pumped the pedal for fuel prime? (accelerator pump)

AuroraGirl said:

Do you have the original distributor? I would say try that..

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I do not.

squaredeal91 said:

Have you pumped the pedal for fuel prime? (accelerator pump)

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Yes. It’s sputters and gets real close to firing but won’t.

Rich77 said:

Yes. It’s sputters and gets real close to firing but won’t.

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loosen the hold down bolt so that the distributor will turn with force, but not on it's own. Crank the engine while turning the distributor slightly clockwise or counterclockwise until it fires off. Once it has fired off, set the timing with a timing light.

Alright, I turned it over to tdc again.
The rotor was 180 (but that doesn’t mean it actually is 180).
So I pulled the distributor and reset it again.
I cranked it over, and it backfired in flameballed out of the carb.
I don’t have anyone here to crank it while I turn the distributor, so I loosened it, turned it, tightened it and cranked it.
I did that several times in small increments clockwise and counterclockwise as far as I could get it to turn.
All it will do is sputter and backfire out the carb.
I took a video of what is happening to the carb while I crank it but I can’t post it.

So I guess that means that I am actually 180 right now??

Rich77 said:

Alright, I turned it over to tdc again.
The rotor was 180 (but that doesn’t mean it actually is 180).
So I pulled the distributor and reset it again.
I cranked it over, and it backfired in flameballed out of the carb.
I don’t have anyone here to crank it while I turn the distributor, so I loosened it, turned it, tightened it and cranked it.
I did that several times in small increments clockwise and counterclockwise as far as I could get it to turn.
All it will do is sputter and backfire out the carb.
I took a video of what is happening to the carb while I crank it but I can’t post it.

So I guess that means that I am actually 180 right now??

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If it is backfiring out of the carb, you are 180 out. It was trying to fire before and not backfiring, so you just needed to turn it a bit, then try to crank it. You don't need someone else there, just turn then crank, turn then crank.

Remove #1spark plug. Tightly stuff a shop rag into plug hole. Tightly! Bump starter over with key till you hear it pop out the rag and stop. Look at the timing mark and if it's off adjust it at this time to near the 0° mark. Now you should be TDC compression stroke.
Now your rotor should be pointing to the #1 plug wire on the cap. If it isn't then you can restab the distributor to align it or rewire the plug wires from where the rotor is now pointing. Remember 18436572

I had a suburban that was acting kind of similar and it was driving me nuts. I had the distributor cap off and would crank the motor and see that the rotor had moved, so I thought I was good. I ended up pulling the distributor and found the gear on the bottom was worn out. The distributor would change position, but it would slip as soon as I started to build oil pressure, since the pump is run from the distributor.

I would see if you can have anyone watch the distributor and make sure that it rotates correctly while cranking, or use your phone and take a short video. I was chasing my tail until then for much longer than I care to admit.

I would also start from step one and reinstall the distributor as if you had never done it before. There are really good write-ups. Much better than I could write.

I would also verify you are getting a good strong spark with the plug grounded off the block or exhaust manifold. The intake doesn't usually work well since they are often painted or aluminum.

I feel like you are close, we are just missing a step somewhere.

So my buddy, who owns a shop and builds hot rods, stopped by yesterday.
We went through the TDC/distributor process again.
It took a little tweaking of the distributor but we got the engine fired up.
However, it won’t stay running or idle.
As soon as you let the key go and take your foot off the gas it will die.
One piece of information that I didn’t share with you earlier is that there’s no exhaust installed yet.
My buddy thinks I need to get the exhaust installed to create back pressure to keep it running.

I'm assuming it stays running if you hold the key cranking starter. Could be ignition switch maybe?

squaredeal91 said:

I'm assuming it stays running if you hold the key cranking starter. Could be ignition switch maybe?

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Yes.
Hmm, could be the ignition switch??

Rich77 said:

Yes.
Hmm, could be the ignition switch??

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Run a fused hot wire to coil from battery.
See if it stays running

Contrary to the older belief, you do not need back pressure for an engine to run. You may need to make adjustments to timing and the carburetor to make it run right, but running straight manifolds or headers won't hurt it. Now if you have an engine that is tuned properly with an exhaust on it, removing that will make it run poorly if you don't tune it for the lack of backpressure.

Once you have the ignition figured out, I bet you will need to make some carb adjustments...

Alright, I ran a wire from the battery aux + to the coil +.
The truck is firing/turning over the same way.