Gas Tank Crushed!!!

soonercrew · 11-09-2010, 08:43:04 AM

my 72z28 had an issue today... finally got the car started today after a 2+ year restoration! looking amazing... sounds great... BUT!!! after the car was running good, we then hooked up all the vac lines and restarted the car... oops! fuel tank then crushed after a minute... the car has the charcoal canister and all vac lines hooked up... we used a NON VENTED gas cap. this car is all original equip... the line was checked and it is NOT plugged up. any thoughts on what could have caused this? i'm ordering another eec tank and fuel sending unit today, and dont want to destroy another tank! im not interested in rigging up some hole or similar in the tank, as this is an all # match car. but, i would be fine with just plugging it if you think that would solve the issue??? any help will be greatly appreciated!!!
thanks,
scott

Camaro4life18 · 11-09-2010, 01:35:41 PM

Try a vented gas cap I guess. I can't believe there is enough suction off the fuel pump to cause that much of a vacuum to crush the tank.

Lerchinator · 11-09-2010, 03:02:00 PM

Put a plastic gas can out in the sun with the vent closed and soon it will look bloated. This is because the tempuature change has caused the liquid gas to turn into a vapor that takes up more room than in the liquid state. As it cools it will turn back into a liquid or you may pop open the vent and hear alot of air.

Now thinking of that fuel tank something similar must have happened the tank got just enought heat to cause the fuel to turn into a vapor this will want to force air out a vent. If it could have vented out somehow it would have taken air out of the tank as it did. Then when the vapor that was inside the tank that has taken place of the air cooled down it will turn back into a liquid and take up alot less room wanting to create a suction. If the air is not returned into the tank fast enough when this happens than it could crush. If there was a rag or a bolt in the vent line or it was crimped then the inside air would have made it out ok and then when it turned into a suction as it cooled it would have needed more volume to vent.The gas cap would also come into play here as well.

You can do something similar with a empty beer or soda can:http://www.stevespanglerscience.com/experiment/00000043

soonercrew · 11-09-2010, 03:24:23 PM

i agree... but, the car only had gas put in it about 30min before it was started (for the 1st time during the 2yr resto). the temp has only been upper 60's, and i couldnt imagine anything heating up quick after only 30min or so... maybe im wrong tho... probably just going to plug the system

soonercrew · 11-09-2010, 05:29:58 PM

found out that we are currently using canister # 7030541 should be a 7030605
the one on it is for a 71 model, and it was changed to the 7030605 canister in 72... would this cause the issue?

6pak69 · 11-09-2010, 05:33:00 PM

Are you a hundred percent sure on the line routing.Do you have the right Holley? On my 70 it has a fitting which hooks into the vacuum. Do you have the correct cannister? The little black box in front of the gas tank?Its a head scratcher for sure.

soonercrew · 11-09-2010, 05:53:50 PM

Line routing is correct, the holley carb is the original and correct, charcoal canister is for a 71 (but should still work same as the 72 as the only real change was part #), black box in front of tank? Are you speaking of the vapor canister behind the rear seat?

6pak69 · 11-10-2010, 01:17:15 AM

Quote:

Originally Posted by soonercrew

Line routing is correct, the holley carb is the original and correct, charcoal canister is for a 71 (but should still work same as the 72 as the only real change was part #), black box in front of tank? Are you speaking of the vapor canister behind the rear seat?

I think so. In 1970 they were mounted in front of the tank on the floor board---mike

Rene Melten · 11-10-2010, 02:51:49 AM

Without a vented cap the system should look like this, borrowed the pic. from a member here.