Weird thing that's been happening lately with my 89. Every time I go to unscrew the gas cap I notice a huge discharge of air/fumes from inside the gas tank. It literally blows the gas cap out of my hand. I've done some research and could really only narrow it down to a vent valve on the tank or a vented gas cap. Not sure with which I should try first. I've also looked into the vapor canisters and all the smog equipments but I was told from a fellow mechanic that I would need to worry about those if the gas cap was like a vacuum and sucking air in.

So any advice would be appreciated. Its warming up here so I'm wanting to take it out driving.

 

Nobody?

 

I would try a new gas cap, it seems like it's not breathing like it should. My Four wheeler gas cap did the same thing. I got a new one and it has been fine ever since.

 

yeah, the chevy cavalier that i just traded in to the dealership for my truck did that too, its just some vents either in your stock cap, fill tube or off the tank itself that is not working, just get a venting gas cap...you are just getting pressure buildup that doesn't have a way to vent out.

 

Your tanks are crossfilling.

 

I replaced the gas cap and still seem to have the same problem. I read the way how the fuel system relieves its self is through a purge valve on my intake connected to my emissions and charcoal canister.

I have removed my rear tank so how would they be "crossfilling"?

 

wow, your problem is beyond me now. Sorry

 

I would start looking at your vent tube on the filler neck to see if it is kinked. If you have an EVAP system (charcoal canister), I would check out the lines that go to that as well.

My wife's '99 Honda did this and we tried a new gas cap, no joy. Still happened. Turned out that the EVAP valve was stuck causing excess pressure buildup.

 

Lenn is leading you into the right direction, Travis_CO.

Also I doubt you can even buy a vented cap today for
your 89 or anything built after the charcoal canister was
installed.

 

I think your problem lies with your charcoal canister. I thought about removing mine and so I took it out and plugged the line going to it just for a little bit because I wanted to see if that line was a vent line. After about an hour I pulled the plug out and a ton of air rushed out. The charcoal canister takes all of the fumes from the tank as it expands and puts them back in the intake, and apparently that is how the tanks "breathe". See if that line is crushed or stopped up or if your canister is clogged you can take it off and put a small breather at the end of the line.