[bsblguy]

Working on my '78 TA I noticed a problem when starting to put it back together after I painted it. I recently put in a new cam, lifters and timing set. I already installed a Holley Sniper Quadrajet fuel injection with Holley in tank fuel pump and all new fuel lines. Pump puts out about 60psi. Ran it to break in cam while car is on stands. Everything seemed fine. Then I got under the car and saw that the fuel tank is deformed. I had it all out and cleaned it when I put in the new pump. Looked almost new. The line going to the charcoal canister is still there. Shouldn't it vent there? Seems like the pump is trying to suck the tank into itself. Don't want this to happen to the new tank I will have to buy. Thanks for any input.

[Scott Stoneburg]

Check to make sure the line to the charcoal canister or the canister itself isnt plugged up. I dont know much about the canisters or how they are internally plumbed, but sounds like you have a vent issue.

[Tom Vaught]

I have seen a vacuum pump used to drain gas from test vehicles collapse the fuel tank to the size of a ring binder. Technician forgot to take off the gas cap.

So in your case, if the tank looked fine when you first got it and now is deformed I would say you have a plugged tank vent (line or fittings to canister), or too small of a vent.

Some Canister type production systems used multiple vents on the tank.

How do you know your canister is not plugged or the line to the canister is not plugged?

Tom V.

[bsblguy]

Sorry, I forgot to mention before I posted this that I have the old tank out, checked that the line is clear to the tank and also checked the line to the canister. Also checked that the canister is clear between the two larger ports. The factory pump had a return line back to the tank which is no longer there. It shouldn't vent there anyway. That line went into the original sending unit that was replaced with the Holley fuel pump/ sending unit.

[Formula8]

How are you venting the tank? My understanding is that tank vapor is drawn from the tank up to the front of the car through your canister and into your carb. Earlier cars used the gas cap for ventilation. Obviously, you do not have a vent in your system. Sounds like you are relying on the vacuum in the tank to draw air from from the cannister. Not sure it works that way.

[bsblguy]

Not really sure how they are suppose to vent. Everything is connected the same as it was with the carb only difference is the in tank pump and no return line. looked at my '76 TA and it just has line from tank to canister then to carb. Is it possible that the return line compensates for what the pump takes from the tank? I wouldn't think so but I am at a loss for what caused this. I have talked to several people with sniper fuel injection and they loved it. Nobody said anything about tank venting issues. I will call Holley and see what they say.

[Formulajones]

Pictures of how you have your charcoal canister hooked up would help. Also pics around the tank and how those lines were plumbed would help. If hooked up and functioning properly it's more than enough vent. It could be as simple as your vacuum switch on the canister isn't working anymore.

I run a Sniper Stealth with the factory charcoal canister for my tank vent, using a Tanks Inc in tank system for the fuel pump.
I had to solder some new line connections into the new tank because the aftermarket stuff doesn't seem to come properly equipped to support the old charcoal canister vent systems (had to do this to a few applications now). Once I had everything hooked up properly it vents easily with no issues, feeding a 600hp engine with 1/2 line feed and return using a large 400 lph pump in the tank.

[Skip Fix]

My 78 just uses it to vent no other lines and does fine. The 81 car stunk of gas from it until I hooked up the purge line to the air cleaner. Could not figure out why the difference.

[bsblguy]

I called a friend to look at his '78 and his lines are plugged going to the carb so I guess the previous owner did that as my friend did not. They are just using the canister as the vent. I might end up doing that. My vac switch on top of the canister does not have anything plugged into it. My friends doesn't either. There is a wire that has been cut that maybe went to it. What wire colors go to that plug? I tried to find a diagram of that wiring with no luck. I have a '75 shop manual but not a '78. The earlier cars did not have that setup. I'll put the new tank in tomorrow.

[bsblguy]

Put the new tank in. Double checked everything. Should be the same as it was with the carb on and no problems then. Started engine with gas cap off. Put my hand over filler neck and there was suction. Shut off engine and removed line to canister and capped fitting at FI unit. Restarted engine and no suction at filler neck. Guess that's how it's going to stay.

[Tom Vaught]

GOOD JOB, THAT IS ABOUT AS BASIC OF A FIX AS YOU CAN GET.

Step #1 This way does not work.
Step #2 This other way does work.
Step #3 Leave it alone now that it is working properly.

(The vehicle is trying to tell you something are you willing to listen? Some people are not able to say yes here.
In your case, you were, Good Job!!!!!)

Tom V.

[Skip Fix]

I think my canister in the 78 is basically just a long vent.