cc347stang

Hi STANGERS!!...I got a good one mind puzzler!! I've had my 91 stang LX trunk for about 6ys now I've redone the car from top to bottom in and out front to back.For the past 2 summers if I have half or a full tank of gas and corner hard (road track/street) gas just SPILLS out the filler neck,the tank seems to build up pressure and causes the gas to spill out.The hotter it is the more pressure it makes in the tank.The only modz i have done when this all started was braided fuel lines at the rails and a fuel pump.If anyone ran into this prob or no of any tips or suggestions would be appreciated!!

Things I have tested and trouble shot
1 replaced gas cap with aftermarket & Ford
2 checked for kinks & blockage in lines (none)
3 inspected and tested roll over valve (ok)
4 filler neck is all there
Thankx!!

Project 5.GO!

Check the rubber grommet that seals where the filler neck enters the tank. These get old and crusty, and get messed up commonly when the tank is taken out to replace the fuel sending unit or fuel pump.

mjr46

run a koer test and see if it flags a code for evap purge valve stuck closed and or related, I can't remember if the eec iv monitors the valve I know it doesn't monitor for evap leaks, but make sure your evap canister and vent valve are all working

Js88lx

+1 on rubber grommet!!!

AdderMk2

filler neck grommet