Saddle Tanks Overflowing After Fueling

[ahoke]

Hi all,

Picked up a '72 C20 Custom Camper this summer with the two additional travel tanks added on either side of the bed. When I purchased the truck, the owner said he didn't use the cab tank because it smelled like gas when he did.
Essentially once I fill up, I'll drive it and park it and some time later one saddle tank or the other will overflow, leaving a slight puddle of gas on the ground. When parking I'll look underneath and there will be no sign of leaking but then coming out of the grocery store, for example, there will be the leak 20 mins later. Anyone have any similar issue? Curious if I just need to replace the 4 way brass tank selector valve or if it's more than that. Also I never fill the cab tank since the previous owner mentioned the fume issue. Initially I thought maybe the valve was bad and the fuel left in the cab tank was slipping back into the saddle tanks due to gravity and maybe it takes that long for the fuel to accumulate into the tank that I'm using.

If y'all suggest trying a new valve any suggestions on where to buy one? Seems like a marine part. I imagine it'll need to be 3/8 inch since it's a 350 sbc?

[Sheepdip]

Expansion

[Stocker]

My K20 also has twin saddle tanks. I have never experienced the problem you describe. Maybe your tanks are just being overfilled, and like Sheepdip said, expansion.
Maybe you can get lucky and catch it dripping, then you'd know where it's coming from.

If it is a bad valve, those are available. RV supply places should have them, and a Google search will definitely find them.

[Sheepdip]

That cab tank smell is very fixable. No telling how long any residual fuel has been in there but by removing the tank and cleaning it, replacing any evap/fuel line hoses a new sender/pickup tube and gasket you should be good as new.

[kwmech]

You didn't mention where the tanks are leaking. AND I would check into where or why the cab tank smells.

[PbFut]

In 1972 return lines were used in the fuel system. This circulated the unused pumped fuel back to the tanks to reduce vapor lock. Auxiliary tanks may or may not have been properly plumbed to receive the return fuel. The valve needs to be stacked so that the selector switches one circuit of supply and one circuit of return fuel in sync and directing to the correct tank. Often the return was not switched on aftermarket tanks and the return fuel simply went back to the main tank. So the owner had to always run the main tank low, then switch to Aux. Then back to main to finish using the returned fuel. It is possible the PO changed the return line to enter one of the aux tanks and you are over filling when using a different tank. Or the return lines got mixed up during a repair. Given you describe overfill after driving for a period of time, the above seems to line up.

[Dead Parrot]

Check for an "always on" connection between the tanks. Either a direct hose connection or a bad/leaky valve. Fuel can flow from the uphill side to the lower tank. If both are full, it doesn't take much fuel to overflow the lower one.

[GASoline71]

Could be as simple as an old cracked rubber fuel line. Check them all.

1971-72 also has an "EEC system" (Evaporative Emissions Control) that vented the tank through a series of tubes and though a charcoal canister, instead of venting out of the gas cap like 1970 and earlier. Not sure if that system would affect the extra tanks in the bed, but if faulty/clogged/rotten could be contributing to the "gas smell" in the cab.

Gary

Gary