backfiring in 29 pickup

[poolnut]

First i had rust in gas tank lots of problems Then i had the tank cleaned and coated at a radiator shop with a good rep. Put gas in tank and took a nice drive Everything is new concerning the fuel system When i put gas in it again i drove about 300 ft and i had my same old problems backfire cutting off It idles fine until i gas it or till the motor warms up Im lost on what to do next Help needed

 

[tdlmomowers]

We had the same problem with a 28 sedan. We finally replaced the distributor cab and it cleared right up. Some of the Repo caps do not have proper gaps between the cap contacts and the rotor.

 

[juke joint johnny]

Have you replaced the condensor? That's what it was on my pickup

John Cochran

 

[steve s]

...It idles fine until i gas it or till the motor warms up Im lost on what to do next Help needed

Did you use the same gas on both fillups?

What happens if you just let it sit and idle? Will it start sputtering and die, or just keep idling?

Have you tried loosening the gas cap?

Steve

 

[James Rogers]

A bad plug will also cause this problem. Some plugs look good but will misfire under a load.

 

[Benson]

Did someone swap the gas tank cap with the radiator cap?

Gas caps are vented ... radiator cap is not vented. THe two interchange but gas cap must be vented.

If gas tank has wrong cap then a vacuum forms in gas tank and gas stops flowing. Then when you stop or idle there can be enough air seeping in to maintain idle but not enough when you go faster.

This is covered in service bulletins

 

[steve s]

If it really runs fine--including idle and acceleration--until it seems to just run out of gas, always after about the same running time, it is running out of gas. Forget all the fine electrically related advice; they can truly cause the same symptoms but not under the conditions you describe.

The next time it dies, hustle around and disconnect gas line at carb and check your flow. That will tell you in which direction the problem lies.

Steve