Fuel tank seal leaks

[AeroNautical]

This'll be the third time ive had to drop my tank to replace the seal where the pump and lock ring are. Each time ive done it, it goes for MONTHS without leaking, having held the tank upside down each time it was replaced to make sure there are no leaks, and one day it always decides after a fill up to start pissing itself. Am i missing something on installation? It can't be anymore centered, and it obviously does work. Its almost like gasoline is eating through the gasoline proof seal.

[1987Comanche]

Dumb question but have you used a square cut seal or round cut seal each time?  If you used all round how about trying a square cut or vice versa?  Fastenal can probably find something appropriate if you take the old one in to match up.

 

  I had this exact problem with Georgia and the seal supplied with the kit was incorrect.  I used it b/c it came with the kit but something didn't seem right. Started kicking myself as soon as it started leaking.  I think the round cut seal is right but wouldn't swear to it.

 

Buna-N O rings will be eaten by gas. Viton will not.

[AeroNautical]

First style i used was square cut, came with the rebuild kit when i got the pump. Second go was round cut, same size, but bought at advance auto.

[A-man930]

I have been fighting this exact problem for years now.  I'll be putting my 4th one on next week.  I've always chalked it up to not being centered, although it sounds like you're going the extra mile and taking the tank out and working with the sender vertically (I'm lazy and don't feel like pulling the tank out   :D

[1987Comanche]

Round cut sounds right now that I think about it.  Did you get the O-ring or the entire lock ring kit?  Also did you lube up the new O-ring with Vaseline prior to install?  How tight does the sending unit fit into the tank without the lock ring retaining it?  It should be tight enough to require a fair amount of pressure/wiggling to pop the sending unit free.

[AeroNautical]

Lock ring kit. No lube, but used a gas proof sealant. Sending unit is tight enough to scare me when i yank it out and am thankful it didnt spark.

[1987Comanche]

I wonder if the sealant is interfering with the O-ring's ability to seat?  It's a pretty tight fit so the ring may not fully seat if the groove has something else in it.  Beyond that my only thoughts are a bent tab on the tank or a weak/broken weld on the collar for the snap ring.   You can pick up a replacement tank for about $100.  Maybe that's the next stop.

[AeroNautical]

Turns out the tank is cracked above the skid plate. I need a new tank anyway. So, I have a short bed, will a long bed tank work? Since I'm at it, I'm sure I can upgrade my 16 gallon to a 23.5 if it'll fit.

[1987Comanche]

Glad you solved the mystery :).  I don't think the LWB tank will fit in place of the SWB 18.5 gal tank.  P/N for the tank is JP5B if memory serves.  I put one in Meg and Maura.  New repops were $100 give or take on Ebay.

[AeroNautical]

I have the 16 gallon, so I guess it really won't work. I thought it might because there is a place for a third tank strap that isn't used with the 16, but to be safe I'll just get another SWB tank. Thanks

[A-man930]

If a big tank fit in a swb I'd so do it. But yea I'm thinking probably not