Leaking gas at the sending unit on the tank

[The Swed]

I rebuilt the tank and installed a new sending unit two years ago. Fuel was sitting at the base of the sending unit mount to the tank today after I filled the tank. Smell goes away at half a tank. Is there a way to fix this other then removing the tank and installing one under the bed?

Thanks

['68OrangeSunshine]

Is there an RTV that's impervious to fuel fumes?
Especially the concoctions they pass off now as ''gasoline.''
Disconnect Batt.
Empty your tank, pull the seat, back or out, which ever works.
With a brass drift pin and light ball pien [no sparks], tap your sender unit out by the 3 lugs, tapping each in succession.
Apply suitable goop to mating surfaces. Re-insert sender and tap back on.

Of course, I'vs seen bad, decomposing filler neck grommets give the same gripe, usually after a sloppy top off.

I hate to see anybody chicken out from using the behind-the-seat-tank. That used to be one of the key points of being a Danger Boy, that you coolly leaned back on 20 gallons of one of the most explosive carburants known to man, and didnt give A F.

To me, putting the tank in the bed is like screwing on training wheels. "...God forbid little Johnny should scrape his knees learning to ride..."

I had a '67 K/10 Suburban and still run a K/5. Even in in the shorter wheelbase '71 Jimmy, sometimes the fuel flow is an issue with the belly tank. In the 127'' wb Sub, it was a major pain. I had to run a 90 gph Holley Red pump in the end.

[Aus69c20]

I have my tank in cab and never get any gas smell.
There is an o-ring behind the sender that may be cracked, perished or missing.
Maybe your gas cap isn’t venting as it should. This would potentially build enough pressure in the tank to create some seeping at the sender.
Good luck

[VetteVet]

I just pulled my tank and the sender out to clean the tank and check the sender. There is an O ring seal under the lock ring that can and should be replaced when it is opened.
I have to get a new sending unit and a new seal plus I'm replacing the filler tube grommet cause it is cracking and looks bad.
Most of the regular auto parts stores don't stock this stuff but it can be ordered online from
AutoPartsGeek.com for a good price. Shipping seem a bit high though.

https://www.partsgeek.com/ymm/1969/c...=fuel_delivery

[The Swed]

I did replace the sending unit and the lock ring which came with the rubber gasket that is visible in the picture. Maybe I had the stack up wrong? It was so long ago.

[Aus69c20]

This is how my seal was. Between the tank and sender.
The previous owner appears to have put anti seize on the seal too.
It never leaked a drop.

[Killer Bee]

I can't tell from picture but is the lock ring fully rotated to the stops and seated?

did you lube the seal and make sure sender mounting plate was centered when locked down?

I would make sure it's the connection leaking and not a penetration in the plate and replace seal..

if the sender fittings are questionable, replace it.. cheap enough..

based on the quality of replace parts these days, wouldn't be surprised if either or both defective

I would not use any sealants or third party sealing aids but rather restore a reliable factory seal..

good luck!

[The Swed]

My stack up is correct... I order new parts and I'm going to replace it with the tank in place and the tank close to full because an empty tank is more dangerous. One parts gas to ten parts air and it's a big grenade. Wish me luck.

[zosoppp]

If you open/remove the sender with the in cab tank over 1/2 full it will pour out of the opening as the sender hole is halfway up the front of the tank.

[demian5]

Often a generous amount of grease is used by GM after installing the sender. I would install the seal dry myself.

[1968aj]

mine did the same thing. Ipulled sending unit up then l lubed the rubber gasket with some o ring lubricant made for swimming pool gaskets. it does not leak now. either it was loose to begin with or in a bind.

[VetteVet]

I use PET, petroleum jelly all my o rings and It works great. I wouldn't worry about the tank exploding because the sender and Lock ring will close the hole. The tabs on the lock ring go under the tabs on the sender and it turns until it seats and the tabs are turned all the way to the stops.

From "Parts Geek" today - Your parts have been shipped New sender, new lock ring and O-ring, and the filler tube grommet. $77 minus $14 for shipping.

Don't know if you guys are aware but there are two sizes of sender lines and fuel lines 5/16ths, and 3/8ths inch . The 5/16th is for the six cylinders and the 3/8ths is for the v-8.