Last fall I bought this nice 1995 4X4 4dr Blazer. The small town dealer told me they had just put a new fuel tank in it. I just figured it was over 15 years old and rusty so this must be a good thing. A few months later I ran out of gas with a 1/4 tank still showing on the gauge. I didn't think much of it at the time but after a few more months I developed a fuel leak at the tank, after closer inspection I found that the bottom of the tank had sucked itself in and cracked. I have ordered a new tank and removed the old one, but I don't know if this is the same reason they changed the tank before or why it is not properly venting, and I don't want it to happen again. Any advise on what to check or what could cause it to not properly vent would be appreciated.

 

Prior to the collapse was there any indication when you filled up that the tank was sucking in air when you losened the gas tank cap ? Like a hissing noise ? Although I have not ever seen this I guess its not impossible to happen if the charcoal cannister is clogged and the vent is clogged. Really strange though. There should have been a check engine light on as soon as the evap system failed to operater properly. Cannot give you much help other then that. I would go back to the dealer and ask them why they changed the tank the first time around. They may have the magic answer. Good luck

 

that is insane, I have never heard of there being enough negative pressure being created to make a tank suck itself in. Are you sure that you didnt hit anything?

 

I never got a check engine light and I can remember hearing a hiss a time or two when removing the cap but have heard this on other vehicles before. As far as hitting something, the entire length of the tank is pulled up and the skid plate was intact under the tank. I did unhook the 2 vent valves on the tank and both seem to be clear, I pulled the cannister behind the rear quarter panel and the vent line that goes up by the filler neck blew some dust out when I blew through it, also it looked like there was some dirt in the cannister where that line hooks in. I disconnected everything and blew through the line to the tank and it seemed clear, then I blew through the cannister where the tank and purge lines connect and was able to blow air out the vent line and vise versa. Not sure about the line that goes to the purge valve, I'm not real clear on how that all works or if I should be able to blow air through it or not.

 

I had a tank collapse on a different make car which was new. It was a manufacturing error, the vent from the charcoal canister was plugged. The fuel pump had enough suction to collapse the tank. You have lost the systems vent.