Fuel tank venting on a k30

[80' 427]

I am having a fuel delivery problem with my k30. I think now after putting in the 454 that the 350 had the same problem. Up top it runs out of fuel. I checked the line for restriction and blew back into the tank. This is when I discovered that it isn't venting cause all the air blew fuel right back on me. With no charcoal canister where is the fuel vent? Is it the cap?

 

[dyeager535]

Only EARLY caps are vented, and at 16PSI which is way too high to run without a real breather. Should be either a breather on the sending unit, or line up to EVAP cannister.

 

[80' 427]

Only EARLY caps are vented, and at 16PSI which is way too high to run without a real breather. Should be either a breather on the sending unit, or line up to EVAP cannister.

It doesn't have a evap canister so I wonder if I am missing the vent some where.

 

[dyeager535]

All I know now is that vented fuel caps seem to be impossible to find...even the charts for Stant(?) gas caps list 16PSI for a 1973, which AFAIK is pre-evap.

Its very possible a K30 would not have had Evap originally, NOR a sender vent, and the cap was the vent, but replacement caps aren't vented. You CAN disassemble the caps and disable the vent, but it's pretty difficult to do without breaking things, but the only choice if the tank isn't vented otherwise.

I've got a friend with a 1973 C20 (heavy GVWR) with "new" caps on it, and it builds up tons of pressure, enough that fuel will vent from the caps. I tried to find correct vented caps, and the aftermarket manufacturers listed non-vented caps.

 

[abig84]

ive had a similar issue on all the diesels i ever owned that i converted to gas. i just drill a small hole in the gas cap

 

[80' 427]

I am going to see if its fixed with the cap off and fix it with a drill or whatever. I had 20 or so psi in it yesterday and it still wouldn't vent.

 

[dyeager535]

Only good thing in my opinion of the caps being vented is that they can probably help keep condensation down in the tank, where simple venting to the atmosphere won't. Not sure how big an effect that will have in reality, just something I thought about.

 

[tipoil]

i drill a hole in mine a few year back,work great,no problem!

what i did is use the smallest bit i could fine and drill from the inside not all the way to the outside. the pressure exit throw the ratcheting gizmo! and no water get in.