Yet another gas tank probelm

[middleagecrisis]

I've replaced my sending unit gasket twice (& second gas cap) now on my '75 Dart, but can't get the tank to stop leaking. Seems like whenever the tank is over half full and especially after it's been driven a while the tank will start leaking from the sending unit. I've got the vent line running from the canister to intake vacuum, so it doesn't seem to leak when running. However, once the car is shut down, it will start to leak. Am I supposed to be using any special sealer on the gasket? If so, let me know what type, since everything I've found say's not to use with fuel. I know it's a poor design to place the sending unit below fuel level, but it had to work properly at one time.

 

[Mrmopartech]

Your problem is most likely the locking ring for the sending unit not compressing the ring enough and when shut down the air pressure in the tank increase and forces out the gas through the weakest link,the seal,which has no pressure from the locking ring,Mrmopartech

 

[middleagecrisis]

Last time I changed the gasket, I made sure both surfaces were clean before installing the new from Mopar gasket. I had to use a screwdriver and hammer to tap the ring all the way into the locking position. I'm not saying that couldn't be the problem, but it was anything but loose. Is the gasket supposed to have vaseline or some sort of sealant put on it prior to install?

 

[Longgone]

I haven`t heard of using any sort of sealant on the gasket, but I have heard of people drilling tiny vent holes in their gas caps. I don`t suggest it, just heard of people doing it to relieve pressure build up in the tank, which may be of help to you.

 

[Cerwin]

Are you sure its leaking from the sending unit?

The only plausable place could be like Mrmopartech said.. the seal on the lock ring.. it might be pinched from how tight you describe it, and if its not that, well maybe your flex line from sender to body line has a small hole in it!

i would wash it down with saopy water so the staines are near gone and let it dry. Once its dry try to make it happen again!
Then pin point it and let us know.. and i have never used sealers either. i replaced my whole tank at the beginning of summer! and its great. no leaks and im running a no vent gas cap! mines a 66 but i think i did hear that later models needed a vented cap... ill have to look into that!


Cerwin

 

[dusterdon]

When I bought my aftermarket fuel sender, it came with a return line hose barb. I hope you have plugged this if you have one. I modified my gas cap to vent pressure with the small holes. Have had zero problems in two years, but we don't go autocrossing. Works fine for going straight. Gotta do something if you have an electric pump.

 

[middleagecrisis]

When I bought my aftermarket fuel sender, it came with a return line hose barb. I hope you have plugged this if you have one. I modified my gas cap to vent pressure with the small holes. Have had zero problems in two years, but we don't go autocrossing. Works fine for going straight. Gotta do something if you have an electric pump.

I'm running the vent line to the charcoal canister and engine vacuum to to the canister. That set-up keeps the tank from building too much pressure when running. Obviously it's not doing any good with the car shut off. The return line has been capped. I'm hesitant to drill vent holes in the cap, because I don't want anymore fuel fumes in the garage than I already have. I need to make a trip to the radiator shop to address cooling issues, so I may just drop the tank and take it along also.