I made some changes to my fuel cell venting because it was causing a spill when I filled it up. It never came back thru the filler neck but when the cell was full it would splash onto the ground. I tried a roll over valve but that does nothing when you're filling up, it would smell real gassy & spill onto the fuel cell & ground. I tried running a hose off to the side with a small filter but it still leaks so I just capped it for now. I've been installing a 3rd member that I just rebuilt with 3.25 gears & a G-Force locker & noticed that fuel was leaking from a fitting before the fuel pump (which is probably on the same level as the fuel cell. Just to try something I opened the filler cap & I could hear pressure escaping from the tank & the leak stopped. So, do I need to figure out something better for the vent, get a vented cap or try plan "C"?, & that's where you guys come in, since this is my first ground up frame off rebuilt & far from stock there are things that I've never done in the real world of car repair. I'm open to suggestions, The filler neck is from a 1989 Mustang GT & the fuel cell is from Summit Racing. I've got about 1700 miles on the hot rod & it's still not done but is fun, it's a 1946 Ford 1/2 ton pickup with a 351W, Mustang T5 trans, 1980 Bronco 9" rearend, suicide doors, tilt front end & rack & pinion steering. Thanks chuck
Some photos of your installation would help in determining what is happening and also make coming up with a solution easier but I will take a guess. If the fill neck is any distance above the top of the tank itself you need to run the vent line up to that level as well or, alternatively not fill above the top of the tank (which is probably going to be a little difficult to monitor if the fill neck has any sort of length). If you run the vent line to just below the cap level and put a double pig tail loop in it at that point you should be good. Roo
I should have thought of that. I'll add some photos of before & then after so you can see the layout. The filler neck rises about 9 or 10 inches above the fuel cell but as you can see the opening in the bed floor is close to the cell so there isn't much room to run a vent hose upward. I'm wondering if a trip to the wrecking yard to try & find a good carbon canister to vent the gas fumes thru would work? Any way here are the photos, hope they help. chuck
Image pulled from the web, I did something like this in hardline. If it's wrong, someone please tell me.
while you are at it put a ground wire to the tank. not only is it a good idea to have one but if you should ever race it its nhra mandated.
Racer X that's what I was told, too. Anyone try one of the sending units? A working fuel gauge would be great.
The vent tube needs to run up and above the tank in a loop before it exists the body and vents externally otherwise fuel will slosh around and leak like there's no tomorrow. You may need to place an additional vent away from filler side of tank. In my 35 phaeton I ran the vent from the tank up through floor to the belt line where it did a loop and then back down exiting through the floor at the area rear near the chassis, tank and fender. Being a PU you need to be inventive and hide the vent tube. You could use the rollover valve and connect the vent line to it. That way there are no fumes that may enter the cab as the vent exits externally. All gaps between body and atmosphere need to be sealed and airtight so no vapours or fumes can enter. It's too hard to pull trim off to photograph however 15yrs now since built and still no issues.
In my Henry J I added the vent to the top side of the fill tube, a simple 90 degree fitting with a single loop rubber fuel line attached.
gas tanks need two vents -- a big one for filling, so that the air in the tank can exit as gas pushes in. OEMs usually have this vent as a 3/4" or so hose from the tank up to the filler neck just inside the cap. the other vent lets air in as the tank empties in use, and lets air in as the tank contents cool. tanks breathe in and out with temperature changes. the two vents can be the same when the filler cap is non-sealed (typical 70's car). in the 60's, the filler neck was large enough (2" +) to act as fill vent, and non-sealing caps allowed breathing. and up high, didn't slosh except when too full. that vent you got needs to go way up high else it will get wet with sloshing. I'm looking at fuel cells to replace my ailing OEM tank but fill and vent issues are a huge and expensive PITA since there's no way I'm gonna have the tank working parts inside the car (eg. filler). it's gonna be under the car or sealed from the trunk. without some way to vent on filling, fuel cells fill super slow. plenty of stories of fuel cell street cars that are a PITA to fill, must be parked at an angle, etc, all from not having good venting. fuel cells with the filler right on the tank don't have this problem because they work like the 60's cars, air just exits the filler because it's so short; a long filler neck/hose lets the gas foam up which blocks the filler, farts and burps and prevents fast filling. I'm thinking that a tube-inside-tube solution might work, but not sure I wanna do all the on-car engineering to find out.
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