Bad Gas or what?

[Gpaw44]

Last week my truck ( 86 GMC 4.8 engine) started haveing a rough idle so I replaced the in line fuel filter and the carburetor filter and added some sea foam thinking it may have some moisture in the tank or bad gaa. The idle smoothed out but now I might be able to go about a mile before it dies. The first two time it died I let it sit for about an hour and it started right up. The third time I did not let it sit but pured a little bit of gas in the carb and it fired riight up and I was able to get it off the street. So I'm thinking is not a electrical issue but a fuel issue.
Is this a carburetor issue or a fuel pump going bad. I can see gas in the inline fuel filter at all times while it is dying.
Thanks for any suggestions for what to look for.

 

[fast 99]

Check fuel pressure and volume.

 

[Grit dog]

Sounds like dying fuel pump. Quick test, when it dies, disconnect fuel line to carb and crank it. If it’s not pumping gas handily then I’d say that’s it.
Although starts and runs again by priming the carb could be vapor lock? But presumably has a return line which prevents vapor lock in most situations.

 

[Gpaw44]

Grit dog, I had thought the same thing about the fuel pump. But I may have also picked up some bad gas so I'm going to replace the pump and the right tank. I am also going to block the left tank and just use the right tank. I am also going have the carb rebuilt so the fuel system is all new and clean.

 

[Grit dog]

Grit dog, I had thought the same thing about the fuel pump. But I may have also picked up some bad gas so I'm going to replace the pump and the right tank. I am also going to block the left tank and just use the right tank. I am also going have the carb rebuilt so the fuel system is all new and clean.

Ok pump the brakes here…figuratively. Who replaces a gas tank due to bad gas? Unless there’s more to it you haven’t said.
If you think bad gas, diagnose that first. It’s easy.
Put a piece of hose on the fuel pump inlet, and run it to a little can of fresh gas.

Even though your symptoms don’t sound like bad gas. At all.
And you haven’t even said if the pump is old or newer but it’s cheap and likely a failure point.

Again presuming the truck runs well before this issue presents.
I don’t consider a fuel pump throwing parts at it. It helps to have a spare and it is good to have a new fuel pump for reliability. But you don’t even know if it’s the problem.
Other consideration, what you said above is not really a plan. Think about it this way. If doing all of those things fixes it, great, but you don’t know what the problem was.
Also you’re disabling part of the truck (the other tank, whatever block it means). What’s wrong with that one?
If you approach every old car issue like that, you will end up with a “new” car after you’ve replaced or hired someone to replace everything. You’ll also have a stack of receipts that is 3x as thick as it needs to be and an empty wallet.

 

[Grit dog]

Another thing, if you have an original 305 or running or attempting to run with all the OE emissions and controls you could have other issues specific than those 305s. They were more complicated and finicky than the other engines. Plenty of good reading on that on this forum.