Bad Gas???

[FLDBRED]

Ive been rebuilding my truck for the last couple of years. Ive been adding gas on ocasion with a gas can, but I have never run the gas completely down. My progress has me at the point where I would like to actually drive the truck. Problem is, truck strarts but shuts off as soon as you touch the gas. Could it be bad gas? What's the best way to remove the old gas or should I just throw some Lucas in there and let it run down?

[68gmsee]

I'm assuming you can crank it and it will idle okay but die when depressing the gas pedal to increase rpm's. If that's the case, it could be several things:
carburetor accelerator pump not working, float adjustment off, flooding or internally clogged carb passages, vacuum leak, vacuum advance not working properly and ignition timing or points adjustment if you have them.

Eliminate them one by one with easiest first but if you want to eliminate gas as the problem, get a one gallon container of fresh gas and go to auto parts and buy a piece of fuel line the same size as the one that goes to the fuel pump. Place the fuel container under the truck and under fuel pump with new hose going to the fuel pump and to the container.

[sprint_9]

Have you checked/changed the fuel filter?

[FLDBRED]

Thanks for the tips guys! I had the same problem when I first brought the truck home, but didn't worry about it because I knew I was going to change the intake and carb. After changing the intake and carb, the problem is still there. The truck starts, idles down, seems to run ok, but if you even slighty touch the gas it shuts off! I'll try the gas container idea, thanks!

[68gmsee]

HEi or points distributor? Have you double checked the timing?

Since you have replaced the carb be sure and also check the vacuum advance for leaks or not working and for any other possible vacuum leaks. If you have a brake booster disconnect it and plug the hose and even modulator lines if you have a 350 tranny. Basically eliminate any possibility of vacuum leaks.

Last but not least, make sure the fuel pump will pump at least a pint of gas into a plastic container in less than 30 seconds, put a meter across the battery posts while it's idling and insure you have app. 13+ vdc. If you have an HEI, check that it's getting a full 12vdc and you're not using original wire from firewall which is resistive.

[FLDBRED]

Great advice, with this type of help I know I'll get to the bottom of this! Thanks!

[TBONE1964]

If it has bad gas, you will smell it. It has an odor like nothing else you have ever smelled. If the truck even starts then your problem is probably not from bad gas. Bad gas gets thick and will not even burn.

[FLDBRED]

Just wanted to update, all to often people ask a question and we never know how they made out. I disconnected the fuel line and placed it into some fresh gas. At first no change,because the old gas was still in the carb and line. After a few minutes the problem went away, I can now step on the gas without it shutting off! I quess I should remove the tank, not sure I could get all the bad gas out by syphoned it.

Thanks for the help guys!

[elf w/capital T]

Thanks for the update!!

[68gmsee]

Originally Posted by FLDBRED

Just wanted to update, all to often people ask a question and we never know how they made out. I disconnected the fuel line and placed it into some fresh gas. At first no change,because the old gas was still in the carb and line. After a few minutes the problem went away, I can now step on the gas without it shutting off! I quess I should remove the tank, not sure I could get all the bad gas out by syphoned it.

Thanks for the help guys!

Great going. My 68 used to smoke really bad so I did a ring and valve job. Turned out to be bad gas. I also found it by doing the gallon can trick.

Anyway, before you do the gas and tank removal:

A couple of years after I took care of the bad gas problem in my 68, I had a problem with it not revving up. Turned out to be the line between the tank and fuel pump. Actually the line that goes along the frame to the pump. Years of gunk and sitting clogged it up and restricted the gas going to the pump.