Engine Backfire and Won't Run Above Idle
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Junior User
Joined: Jul 2006
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From: North East OK
Engine Backfire and Won't Run Above Idle
Hey friends, hoping someone can help me overcome the frustration I'm currently having here. A couple weeks ago I hauled a trailer half way across the state and back. Upon return I noted water leaking from the intake manifold. It was leaking up front at the junction of the china wall/head/intake. Engine otherwise appeared to run fine. I pulled the intake. In the process of removing the distributor, I damaged the electrical connector to the distributor which necessitated replacing the pickup coil. I cleaned up the distributor and replaced the pickup coil. I also rebuilt the carb. I reinstalled the intake with new gaskets, nothing new, done it before, stabbed the dizzy, also nothing new, and installed the carb. Replaced plugs, dist cap, and added new plug wires. When I installed the coil, I noted a wire coming from the coil assembly that runs to what looks like a condenser was also damaged. This condenser is bolted to the coil bracket mount. I have not addressed it as I doubt it is the issue and I need another terminal if that I possible.
All this said, I can't get this truck to run above idle and I question that the damaged condenser wire is the issue. The engine fires right up and sounds good. Give it a little gas and it stumbles and backfires out the exhaust. Lots of moisture coming out that tail pipe which is also concerning. Dipstick looks clean. See video.
I have double checked my firing order, my plug wires, and the timing. Rotor is pointing to number 1 plug terminal at TDC. I've confirmed with both finger in plug hole with compression pushing my finger out and even stuck a coat hanger in #1 cyl to access piston at TDC with timing marks on harmonic balancer at 0 degrees. Even took a timing light to it and set it for the correct timing. As I rebuilt the carb and have two of these, I stuck an old one on and still got the same results. Also concerning to me is the seemingly excess water coming from the exhaust. See video
Thoughts???
Thanks!!!
https://www.youtube.com/watch?v=iyGv...ature=youtu.be
All this said, I can't get this truck to run above idle and I question that the damaged condenser wire is the issue. The engine fires right up and sounds good. Give it a little gas and it stumbles and backfires out the exhaust. Lots of moisture coming out that tail pipe which is also concerning. Dipstick looks clean. See video.
I have double checked my firing order, my plug wires, and the timing. Rotor is pointing to number 1 plug terminal at TDC. I've confirmed with both finger in plug hole with compression pushing my finger out and even stuck a coat hanger in #1 cyl to access piston at TDC with timing marks on harmonic balancer at 0 degrees. Even took a timing light to it and set it for the correct timing. As I rebuilt the carb and have two of these, I stuck an old one on and still got the same results. Also concerning to me is the seemingly excess water coming from the exhaust. See video
Thoughts???
Thanks!!!
https://www.youtube.com/watch?v=iyGv...ature=youtu.be
FTE Legend
Joined: Nov 2015
Posts: 30,915
Likes: 4,123
From: Angier, NC
I would guess we are taking about a v8 that wall thing but what one?
Is the condenser thing hooked up or not?
I seen a post not long ago that a member had issues when it was not hooked up.
You could pull 1 plug wire at a time and see if the back fire goes away or changes.
I say changes because if you have 2 wires crossed, 302 motor using a 351HO cam, the change the firing order for 2 wires.
Dave ----
Is the condenser thing hooked up or not?
I seen a post not long ago that a member had issues when it was not hooked up.
You could pull 1 plug wire at a time and see if the back fire goes away or changes.
I say changes because if you have 2 wires crossed, 302 motor using a 351HO cam, the change the firing order for 2 wires.
Dave ----
FTE Legend
Joined: Nov 2015
Posts: 30,915
Likes: 4,123
From: Angier, NC
So 351 HO running a 302 firing order maybe?
Bad pick up coil?
I also think someone was able to get a motor to start but not run vary good with the dist. 180* off.
Bad new plug(s)? I have had new plugs that only ran to move the car in & out of the garage.
One day I went to move the car and it idled great but give it a little throttle and it would back fire out the tail pipe.
Because the car sat for long times between running I thought stuck valve. Compression check and all was good there.
IIRC I pulled plug wires 1 at a time till I found the bad plug.
Or I wet the header tubes and ran the motor for a short time with it back firing. Just enough to dry the tubes on the holes that were firing.
Swapped the bad plug to another hole to make sure it was the plug and it was.
I replaced all the plugs even if they all looked new and it runs great again.
What else did you touch? Don't think a carb rebuild would cause this.
Dave ----
Bad pick up coil?
I also think someone was able to get a motor to start but not run vary good with the dist. 180* off.
Bad new plug(s)? I have had new plugs that only ran to move the car in & out of the garage.
One day I went to move the car and it idled great but give it a little throttle and it would back fire out the tail pipe.
Because the car sat for long times between running I thought stuck valve. Compression check and all was good there.
IIRC I pulled plug wires 1 at a time till I found the bad plug.
Or I wet the header tubes and ran the motor for a short time with it back firing. Just enough to dry the tubes on the holes that were firing.
Swapped the bad plug to another hole to make sure it was the plug and it was.
I replaced all the plugs even if they all looked new and it runs great again.
What else did you touch? Don't think a carb rebuild would cause this.
Dave ----
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Joined: Jan 2001
Posts: 56,984
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From: Virginia
The timing is not too far off. It would not run if it was. It's not going to run 180 out. I would loosen the hold down bolt on the distributor just enough to where you can grab it and move it. Start the engine and then turn the dist till the idle speed goes up a little bit. Then see if that helps it. If it does, do it a little more. Then see what the timing is with the light. Your balancer may have slipped a little bit throwing the marks off. A common problem when they get old.
Thread Starter
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Junior User
Joined: Jul 2006
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From: North East OK
So, I fixed that electrical terminal and plugged the condenser in. As I thought, no change. I then removed the hose going to the vacuum advance and plugged the port at the carb and the engine runs seemingly fine now. Starts right up, idles smoothly and goes through the rpms without issue. So, now I'm really confused. I've always run vacuum advance on this truck, plugging it in to the same port on the same carb. Why now is it causing an issue? I did partially disassemble the distributor, cleaned it up and put a new pickup coil in it as I severely damaged the electrical connector when I was trying to get it out. Wondering now if perhaps I failed to put it back together correctly.
FTE Legend
Joined: Nov 2015
Posts: 30,915
Likes: 4,123
From: Angier, NC
The could be but now you know where to look deeper.
Could hook the hose back up and see if the issue comes back and if so pull the hose, no need to plug vacuum, and with the RPM up put the hose on & off to see if it happens.
if yes you need to look over that pickup coil & wires inside the dist.
Maybe when looking if you have a way to pull a vacuum on the hose do so.
It has to be something inside that moves with vacuum.
Dave ----
Could hook the hose back up and see if the issue comes back and if so pull the hose, no need to plug vacuum, and with the RPM up put the hose on & off to see if it happens.
if yes you need to look over that pickup coil & wires inside the dist.
Maybe when looking if you have a way to pull a vacuum on the hose do so.
It has to be something inside that moves with vacuum.
Dave ----
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