New tank leaks when full

[comanche32]

So I installed a new tank and sending unit. Filled the truck up until it kicked off. Looked under truck fuel pouring down. Got it home thought it was coming around the sending unit. Less than a gallon out of the tank and now there's no leaks. Was it just a overfilled tank somehow. I never had that happen with the old tank.

[ghetdjc320]

Sending unit o ring not properly seated is prime suspect and has happened to me multiple times. Occasionally, the hold down tabs that keep the pressure on the seal can be the culprit. Did you also replace the vent valves and/or gaskets? 

[DirtyComanche]

Unfortunately you'll likely have to put more gas in it and see where it is leaking to confirm, unless you can see clear leaking marking, but I would probably just pull the sending unit lock plate off and look at the o-ring before adding and more gas.

 

If it is from the sending unit o-ring, make sure to put some vaseline on the o-ring before you assemble it.  It will help the sending unit lock ring to slide to the locked position without causing the o-ring to tear/extrude/split.  Look for any nicks/burrs/cracks on the face of the seat in the tank and the lock plate too, as they may also cause the o-ring to fail or be ineffective.

 

 

[comanche32]

Its not leaking now everything is dry. The fuel level is above the sending unit. Can theese new tanks get over filled and leaking out the top vent or something else. The whole lock ring and sending unit mount are bone dry and there over 3/4 tank of gas. 

[comanche32]

I also replaced the top vents and seals with the tank

 

[GonzoTheGreat]

I only ask because I have been guilty of this myself, but did you fully tighten the hose clamps on the filler neck hoses?