gas tank pressure

[Oscar the grouch]

Let me start by saying i'm new to this forum but not to these trucks I have a1970 k10 with a 305 4speed and the fuel tank builds so much pressure it causes the gas to bypasses the pump and cause the carb to flood none of my othe c10s had this problem

[DjS71]

Had my tank build so much pressure it popped a seam in the tank. Turns out someone had plugged the hoses to the vapor canister without my knowledge so that when I put a non-vented cap on the tank, the pressure had no where to go.

Simple solution should be to get a vented cap, unless there are other issues at work here.

[Oscar the grouch]

I bought a new vented gas cap and that didn't help did some research and found out that they are not truly vented anymore and found a mod for the gas cap but that didn't seem to help either

[Katrina/10]

When you remove the gas cap do you hear air escaping? I think a 70 cap should be vented, but if not, you can vent it by drilling a tiny hole in the inside of the cap. The hole should be above the pressure relief spring seat.

[LockDoc]

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Does it release a lot of pressure when you take the gas cap off, after you have driven it a while? If the tank is not vented it should create a vacuum and the engine would quit running when you are driving it.... What carburetor does the 305 have on it?

LockDoc

[Oscar the grouch]

Yeah it builds pressure when driving or sitting the carb is a carter afb competition and the truck will sometimes stall when coming to a stopsign or even making a turn

[Oscar the grouch]

Sorry it does release air when I take the gas cap off

[geezer#99]

Originally Posted by Oscar the grouch

Yeah it builds pressure when driving or sitting the carb is a carter afb competition and the truck will sometimes stall when coming to a stopsign or even making a turn

You need a fuel pressure regulator set at 5 psi.

[jeffahart]

Your cap is probably venting just not much. Not venting much should not be an issue for the tank. The tank and related components should be able to expand and contract, or hold pressure, with the gasoline and not be an issue. My tank has pressure. But I know what you are saying, it seems like the thing might explode. I've been in sports where you haul around a lot of gas cans. I sometimes look at some of the bloated cans and think to myself... why aren't you exploding? That said, if it were a safety issue or something that caused problems within the fuel system, then there would already be a fix. And there is, the vented cap. I just don't think they vent much, just enough. Vented does not mean no pressure.

Edit oop

[AnotherWs6]

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

Great six dollar investment for me. Peeled the sticker off and it looks good, not show quality chrome but still pretty damn nice. I get a liiitle pressure build up if it's super hot out, but nothing that effects drivabilty. I mistakenly bought the same one in non vented version. It was on there when I swapped my fuel pump and carb. Got the old equipment off on a Sunday and left it apart. Came home Monday...... could smell gas when I was getting close to my driveway. It pumped a lot right out of the open fuel line. Doh!

[Katrina/10]

Originally Posted by Oscar the grouch

Sorry it does release air when I take the gas cap off

Then your cap is not vented. Take the cap off, or loosen it and go for a ride and see if your symptoms change.