I need help figuring out this gas leak.

[aggressive male]

I have a cadillac with throttle body injection and the fuel pump mounted to the frame. I noticed that while it was running fuel was dribbling down the gas tank but when I shut it off it would stop dribbling. I figured it must be a leaky fuel return line. So I disconnected the fuel line at the engine so that I could run the fuel pump to drain most of the gas into gas cans. I figured I might deform the tank taking it off while it's almost full. So now that I have the tank off but still attached to the gas lines I turn on the fuel pump to see where it was leaking. I can hear the fuel going through the lines pouring into the tank but it's not leaking now. How could this be?

[paul67]

lack of back pressure as its not feeding the injectors maybe ?

[Chevy]

I have a cadillac with throttle body injection and the fuel pump mounted to the frame. I noticed that while it was running fuel was dribbling down the gas tank but when I shut it off it would stop dribbling. I figured it must be a leaky fuel return line. So I disconnected the fuel line at the engine so that I could run the fuel pump to drain most of the gas into gas cans. I figured I might deform the tank taking it off while it's almost full. So now that I have the tank off but still attached to the gas lines I turn on the fuel pump to see where it was leaking. I can hear the fuel going through the lines pouring into the tank but it's not leaking now. How could this be?

Maybe the leak isn't in the fuel return line but in the tank--and now that the tank is no longer full you don't see the leak because it's high up on the tank?

good luck at any rate.

[aggressive male]

Thanks for the replies guys! I think I found the problem but not sure. I took out the fuel sending unit and that O-ring that goes between the tank and the sending unit was partially out and hanging in the hole. So if I slammed on the brakes I guess it was leaking out, I didn't have anyone look so I don't know. I think if I remember right I had a hard time getting that O-ring in last time because it was slightly too small but it seems to be stretched out correct size this time. Is it possible I could have used some octane booster or fuel system cleaner that changes the size of rubber parts like that? Thanks

[paul67]

If I were you I would buy a new 1 as it's probaly lost its integrety remember the shuttle.