Weird sputtering issue

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Twisted71

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Hey all,

I have been working on a weird sputtering issue in my 71 duster for a long time.
The car will start and run fine when the engine is cold/warm.
I can stand on it when I first get it out like this and it does not sputter.
After the car warms up though, it will start to sputter and get worse the longer I drive it
and the more gas I give it. I have to roll to the side of the road and wait about 10 minutes and then it acts better but still sputters as I limp home.

I know what most of you are thinking, Vapor Lock! So here are some things
I have done to it to chase this "demon". 8)
I have raised the carburetor with some spacers, ran a return fuel line to the gas tank, got rid of the electric fuel pump and went back to a mechanical fuel pump (I hated this thing anyway - noisy), made sure that the fuel lines are not near the headers, and added a manual choke. After each of these changes, the problem still exists. Could it be something simple like the gas cap seal? I think next I will resort to rebuilding the carburetor. Maybe one of the floats has a hole in it.?? It's just weird. She will start and run fine when the engine is cold, but I don't dare drive across town unless I have time to stop along the way a few times! :pale:
Thanks!
 
Twisted71 said:
Hey all,

I have been working on a weird sputtering issue in my 71 duster for a long time.
The car will start and run fine when the engine is cold/warm.
I can stand on it when I first get it out like this and it does not sputter.
After the car warms up though, it will start to sputter and get worse the longer I drive it
and the more gas I give it. I have to roll to the side of the road and wait about 10 minutes and then it acts better but still sputters as I limp home.

I know what most of you are thinking, Vapor Lock! So here are some things
I have done to it to chase this "demon". 8)
I have raised the carburetor with some spacers, ran a return fuel line to the gas tank, got rid of the electric fuel pump and went back to a mechanical fuel pump (I hated this thing anyway - noisy), made sure that the fuel lines are not near the headers, and added a manual choke. After each of these changes, the problem still exists. Could it be something simple like the gas cap seal? I think next I will resort to rebuilding the carburetor. Maybe one of the floats has a hole in it.?? It's just weird. She will start and run fine when the engine is cold, but I don't dare drive across town unless I have time to stop along the way a few times! :pale:
Thanks!
Click to expand...
You mentioned gas cap, I have had an issue in the past with a customers car where the fuel tank was not vented and you could actually see the fuel tank would suck itself in because of such a vaccum inside of it. Take the car out without a gas cap on and see what it does. Its a long shot but its an easy test.
 
I like the gas cap suggestion! I have seen this on a motorcycle once.

Don't overlook the ignition coil as a possible cause.
 
Thanks everyone, I'll try these things tomorrow... Speaking of the coil,
I posted this earlier on another post:

Maybe one of you knows the answer to this...

Years ago, a good friend of our family showed me how to "ground the coil"
on my 65 Barracuda to serve as a poor mans anti theft device. He helped me rig a switch hidden under the dash with a wire going through the firewall to the coil. If the switch is not "on" the car will not start. I can't remember if the wire went to the positive or the negative side on the coil. I think the other wire from the switch went to ground.
 
Twisted71 said:
Thanks everyone, I'll try these things tomorrow... Speaking of the coil,
I posted this earlier on another post:

Maybe one of you knows the answer to this...

Years ago, a good friend of our family showed me how to "ground the coil"
on my 65 Barracuda to serve as a poor mans anti theft device. He helped me rig a switch hidden under the dash with a wire going through the firewall to the coil. If the switch is not "on" the car will not start. I can't remember if the wire went to the positive or the negative side on the coil. I think the other wire from the switch went to ground.
Click to expand...


you would spice it to the positive side of the coil, but you would be better off with a hidden battery disconnect.
 
blackbomber said:
I like the gas cap suggestion! I have seen this on a motorcycle once.

Don't overlook the ignition coil as a possible cause.
Click to expand...
Yup, first find out if it's fuel or ignition. A timing light helps here. Check each plug and the coil for a spark miss.
 
Hi all,

Well I took it out again today and it was fine for the first 15-20 minutes.
Then it started sputtering so I pulled over and felt the coil and it was not hot.
I also removed the gas cap and there was a good amount of pressure that escaped. I left the gas cap off but it didn't seem to help.

Same as before, I waited about 5-10 minutes and the car started and
ran fine till I got it home.
:scratch::-k

Thanks for the info on the coil grounding. Positive side sounds right.
 
Isn't this old car thing fun...........sometimes not. LOL
 
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