long time reader first time writer i have a 89 formula 305 tbi there is a strong gas smell at anything over a 1/2 tank when car is running, worse when you speed up and let off the gas. i see no signs of a leak anywhere even with a full tank. the car shows signs of a hard wreck in the past (lt quarter) and suspect tank was bent and as time pased rusted i bought a posi to go in so now is the time to change the tank(and pump) will a later tank fit like a 4th gen or just look at new aftermarket,or is there somthing else to check thanks for any help

 

About time you shared!! Welcome to the board! where do you smell the gas? in the car? outside? Under the hood? Have you visually checked the tank? Is the charcoal cannister in tact? (black cylinder thing ,drivers side,engine bay behind the driver headlight....

 

thanks man yes traced fuel lines inspected as much of th tank as you can see the smell is strongest with car running and windows down but can find no leaks under hood also put rear hood seal and scoop cover back in no change thanks for the welcome

 

woops yes also checked canaster even took it loose did not feel like it was wet

 

there is a vent line from the tank connected to the cannister..if it came loose it could cause a smell. Is your gas cap sealing properly? Im not sure about the 4rth gen tank..there are a lot of third gen tanks out there. Check the boneyards....seems if the tank was leaking you would be able to see it....strange problem here..

 

Believe me; you would have to absolutely destroy the rear end to damage the tank. However you said the quarter panel looks damaged, was this on the gas filling side?
The wreck could have cracked the filler neck in a way that doesn't leak when filling, but fumes can escape (i.e. along the top). It could even have a separation where the filler neck goes into the tank itself.
Check into that, cause I think you can get just a filler neck at your local parts store without buying the whole tank.

Ron

 

Also by the filler neck there is a little plastic vent checkvalve, if it is broken or missing it would cause a strong gas smell, especially when running.

 

thanks for some other ideas . found the damage when redoing the int they replaced lt quarter, fuel filler side ,but left a bend in rear floor panel. i work at a GM body shop so we checked it on a frame machine car is square but that damage is right over fuel tank. i work on the car at the shop so i cant leave it sit i try to have anything i might need there so as not tie up a stall. but i dont understand why i only get the smell with over 1/2 tank and car running. the techs i work with are just as stumped. wheen i do find it i`ll pass it along thanks again