Leaking Gas Tank

[torqueaddict]

Guys I got my motor tranny gears and new gas tank installed last year. I have put under 100 miles on my car since however I was going to get a wheel alignment and my buddy told me I have a really bad gas leak coming from my gas tank. When I pulled over I could see the leak was so bad a puddle had formed in the two seconds I was stopped. It looks like its coming from the top of the gas tank but I really cant tell. My gas tank sending unit and gromit are all new, what could it be? I wanna take it to the shop that did the work but I really wanna cut ties with them because the owner is a criminal ( or not a very good business man would probably be a more fair description). Any ideas or suggestions on my next step It may be cheaper to just buy a new gas tank and install it myself but if something is not connected right that would be the easier solution.

[dutch]

I`m not sure about the 72 tanks, but on my 70 there is a drainplug on the top in the middle.  it shouldn`t be leaking when you stop driving if that one is missing.  There are only a few places it can leak, unless it`s got a fabrication failure. If it is hard to see where the fuel comes from, you could clean it up and use some tallow powder to help you locate the leak.
It`s not too difficult to drop the tank. drop the rear valance and the 2 straps. a couple of lines and the fillerneck.  Be carefull with the weight of a full tank.

[Super Blue 72]

I would make sure that the tank is not leaking from the sending unit on the side of the tank.  From what I recollect, some people prefer to use the old lock ring as the new ones don't seal as well. 

When you saw the leak, was the tank topped off?  Was the puddle on the driver's side of the tank?

As far as I remember for a '72 tank , there is no drainplug on the top.  There are 6 openings: sending unit hole on the side, gas tube inlet and 4 vent nipples.  Doe you have all 4 hoses hooked up?

Make sure you know what general area the gas is leaking from.

[Chryco Psycho]

 
Make sure all the hoses are connected or make sure any open nipples are plugged

[4 speed fish]

I had the same issue.My filler neck grommet got sliced when I put the filler neck in,the grommet was new but it was real hard,the replacement one was very soft and easy to put in,the first one was dried out from self life.

[torqueaddict]

Sorry Guys I think I forgo to check to e mail me when people respond to the post. I havent really got around too playing with this. I actually have a 70 tank in my car, they told me it would work fine so I hope thats not the cause of this problem. It could be the sending unit or the gromit, it just seems weird that they werent leaking when the tank was installed originally. This Friday when I adjust my A arms I will really dig in on the tank issue I was kinda just looking for some perspective on possible solutions and possible causes. Guys you are all awesome your support is really appreciated.   

[burdar]

The new sending unit gaskets are thinner than origonals.  That is why there have been leaking issues around the senders.  I don't know if bending the locking ring more would tighten up the connection or not.

If you have a 1970 tank in your car, make sure you have a vented gas cap.  If you have a sealed cap, the tank will build pressure and push out some fuel.  1970 used a vented cap(except California vehicles equiped with emissions) and 71-74 used a sealed cap.

[Super Blue 72]

The new sending unit gaskets are thinner than origonals.  That is why there have been leaking issues around the senders.  I don't know if bending the locking ring more would tighten up the connection or not.

If you have a 1970 tank in your car, make sure you have a vented gas cap.  If you have a sealed cap, the tank will build pressure and push out some fuel.  1970 used a vented cap(except California vehicles equiped with emissions) and 71-74 used a sealed cap.

   Good point, make sure the cap is vented. 

Little story: I put on a locking gas cap that was not vented, got that "whooosh" everytime I opened the cap.  After putting the cap on the car ran rough and on hot days I could really smell gas from the car without the engine even started. 

I noticed I had low oil pressure and I checked the oil and it smelled like gas and I was at least 1-2 quarts over FULL.  I drained the oil and it was like water.  I think what happened is that gas pressureized in the tank and pushed past the carb and leaked down into the engine past the valves.  That's the only thing I can guess at... 

[willard]

Probably the gasket by the sending unit - had the same problem yesterday - car just restored - I took it to fill the gas tnak full and within a few minutes my buddy spotted a real gas lake under the car. The gas wal literally pouring thru the top of the ring:




When we hit it with a screwdriver it stopped - the new ring is smaller dia than th older one ad it can pop off one of 3 tabs.Then it leaks.

[Barracudadan]

Sorry to hear about your tank leaking.I`ve got a 72 with a new gas tank sittin on my workbench waiting to go in,I think I`ll use the old lock ring to be on the safe side.Thanks for posting it gave me a heads up on a potential problem!

[hooD]

I have a 1970 tank on my Cuda.  I had to make sure that the one (1) vent line from the tank went to the vapor separator that is on the frame.  1973 tanks had 4 vent lines.  I plugged the 3 nipples that were not being used on the frame. 

If your tank is not properly vented it will build pressure.  You will hear it hiss out every time you open the gas cap. I had my venting lines wrong and it was pushing raw gas to the charcoal canister.

It could be coming from the sending unit area as others have said too.  Hope you find it.


before removal to fix the float


see the 4 vent lines


clean the lock ring