Fuel Tank Venting

Ok, so I've been having some fuel supply issues, but I'm sorting through them. One major issue that I've found with my carb flooding is that fuel is being pushed by expansion. My carb has been flooding and the extra head on the fuel caused me to have to readjust my float. This is the second time I've filled the tank full, but its the first time I've seemed to have venting problems. I have the vent lines at the tank teeing together and going into an aftermarket rollover/check valve. That valve is supposed to also vent the fumes to the charcoal canister. Thing is, my tank was pressurized because I took the gas cap off and it let out some air. Maybe my new rollover vent valve is undersized? I wouldn't think so since the connection nipples are the same size as the original. I smelled for gas at the charcoal canister and it doesn't reek of fuel smell so I don't know if its doing its job or the fumes aren't venting there.

I ran my jeep tonight to get the fuel level down and I was able to drop my fuel pressure from 8 to around 5-6 psi.

This is the check valve I have but I didn't pay this much

http://www.fuelsafe.com/store/vent-check-valves/in-line-tank-vent-valve-trl7.html

 

I have a 71 CJ5 with fuel tank at the rear and I never understand how it works. On the books there are many system and the 71 is not the same as 73. In my opinion the fuel goes by gravity and is pumped to the carburetor by to fuel pump.
I had some problems of fuel level so I checked, I ha a transparent line to check.

I have an exit for vapor of fuel on the tank, it goes to nothing (directly in the air) but it should go somewhere more secure.
You have normally no pressure in the tank, the vapor goes away through this exit to somewhere near the motor for safety.

That's all my understanding, and I leave it to specialist. But you cannot have pressure inside the tank, it is probzbly dangerous. Or I badly understood your message, I am not enough fluent in english technically.

 

Fuel expands and contracts with changes in air temperature, so when it expands, the air has to go somewhere

 

Is the valve mounted verticaly with the correct side up?

 

Yes, but I'm going to crawl under there and check it (unscrew it) and check for kinks.

 

I kinda doubt your flooding is due to the roll-over valve.

If you worry about venting, remove the valve and replace it with a fuel filter, one end open to the air. That will ensure that your tank is vented. Then see if your flooding is due to the vent or not.

If you have a mechanical fuel pump, they are designed to regulate to a specific pressure, usually about 5 psi. Your typical automotive carbs should not have a problem with that.

When you say flooding, do you mean you have fuel coming out of the bowl vents? Usually that's a sign of a stuck float, not some fuel pressure issue. You have a 304 with a 2100? They seem to be prone to stuck floats. Try adjusting the float tang a little, to make sure it's perfectly parallel with the float pivot, and pushes directly down on the float needle. Bend the float so that you have the right level, and the tang is perpendicular front to back, and side to side, with the needle.

 

Holley 4 barrel 600 cfm

When I say flooding, I mean fuel is being forced through pump while sitting not running and with a full tank. I can disconnect fuel line at carb and fuel continues to come out from tank (under pressure). This extra head made my fuel pressure gauge (between filter and carb) read around 8 psi when i ran the jeep under this condition. When the fuel level in the tank went down some while idling, pressure stabilized around 5 psi.

 

Vent the tank and see what happens. You need a working tank vent.

Check that you can blow through the canister from the tank end. They can get clogged.

 

My 73 does not have the check valve and canister. The hoses are plugged. I also have a return line plugged out of the pump. I think there are different caps for the gas filler- vented and not vented. I would take your gas cap off and check for pressure. there should be none. I have had no problems with my set up.

 

Believe the dang vent valve I installed was upside down. The orientation in the link above and on mfg site don't jive. The orientation in the link above should be correct which is opposite how I had it.

 

My 74 has the same as you describe. My fuel return is not plugged though, but assume the cap I have is not vented. Would I assume correctly that if your fuel return is plugged that your cap is vented?
Only reason I ask is that I am replacing my tank and don't necessarily know what option is best. Any thoughts? Thx!