wnaplay1647545503 Posted May 20, 2014 Report Share Posted May 20, 2014 On my old plymouth the gas tank is in the trunk including the fill spout. It doesnt have windows in the doors and I dont necessarily plan on putting windows in but if I did I assume the fuel vapors would seep into the front unless i completely seal off the gas cap. My question is does the cap make an air tight seal and does the fuel tank need to vent. Someone once told me they believe some caps are designed to allow the tank to breath through them.there is no breath tube anywhere on it so can a fuel system(carb, mchanical fuel pump) work properly without breathing somehow? Quote Link to comment Share on other sites More sharing options...
Cordell Posted May 20, 2014 Report Share Posted May 20, 2014 Depends on the age of the system in question, older stuff before EVAP systems would vent through the cap, but anything for the last 20 years would vent through the EVAP system. So yes it has to vent to prevent exessive pressure buildup. You can get a dangerously swollen fuel tank if it's not vented correctly, albeit not really the norm. New stuff won't even fill correctly if the vent doesn't work. As for your specific application maybe you can just vent the filler neck somehow outside of the vehicle and seal the cap. Would take a little thought to make it work right. Quote Link to comment Share on other sites More sharing options...
vonrottes Posted May 20, 2014 Report Share Posted May 20, 2014 If it does not have EVAP provisions I'd say drill a hole in the top of the tank or on the top of the filler neck and install a Hose barb fitting, vent that into a Charcoal canister under the trunk and use a sealed gas cap. Quote Link to comment Share on other sites More sharing options...
wnaplay1647545503 Posted May 24, 2014 Author Report Share Posted May 24, 2014 I have been running the hole in the filler neck for the last year but I barely ever drive this. I thought about connecting the hose to it and venting it below the floor but if I find a way to seal the cap would this hole be enough vent? Quote Link to comment Share on other sites More sharing options...
Cordell Posted May 24, 2014 Report Share Posted May 24, 2014 I have been running the hole in the filler neck for the last year but I barely ever drive this. I thought about connecting the hose to it and venting it below the floor but if I find a way to seal the cap would this hole be enough vent? If it's what I'm picturing on most gas tanks, yes it should be fine. Quote Link to comment Share on other sites More sharing options...
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