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Discussion Starter #1 (Edited)
Howdy everyone!

New here, but not new to offroading.

Bought a 85 K20 silverado with 37" military tires (since switched to 11.2x20 tractor R1 tires that I took a hot knife to) a completely rebuilt 350 with vortec heads, eddy intake and carb, headers, cam, ect.

Truck is 420-435hp, TH400 trans, NP208 (or 207, can't remember now) t-case, GM 14 bolt rear out of 01 2500, front axle is stock gm 10 with upgraded axles and u-joints and new manual hubs. The truck was 600 and my current total is about 5,200 after rebuilding EVERYTHING and putting on fresh meats, caging myself, welding myself, blah blah.

Anyway, this truck is a dual tank model, but both tanks were gone when I got it. Because I planned from the get-go to mud this and hit trails, I didn't want a tank punctured from sliding into a tree (or other stuff) so I put a 45 gallon fuel cell in the bed behind the cab surrounded by 1 3/4 DOM .120 tubing (its a single cab truck, w/ beer window and S10 seat in the bed between the wheel wells- I really just built it to play around at Muddigras in Huntsville, TX every once in awhile. Didn't have any rules/ classes in mind when I did it.

Anyway, I have an electric fuel pump going from the tank to the engine which is fine- my problem is that there is no evap system or venting system for the fuel cell so of course, it "swells up" in the texas heat and will flood the engine when shut off if you don't shut the fuel off (I installed emergency fuel shut-off valves through the system and bleeds so I can draw gasoline to start camp fires and fill up dirtbikes... shit like that) but I need some way to vent the system so that it doesn't "self pressurize" and flood the carb when off. Currently, I just shut the valves so it holds the pressure and open them only when I want to start/drive the truck which is annoying.

I thought about a one way check valve to let the pressure out... but when im running that would eventually draw a vacuum, starve the carb for fuel and leave me on the side of the trail until I took the cap off to let oxygen inside.

I don't want to just let it vent into the atmosphere, because the stupid ethanol is hygroscopic and will just suck water into my fuel, making it useless. And of course, gasoline would just evaporate out and be wasted.

So, how to I run an evap system to prevent the tank from pressuring/vacuuming while off/running?
 

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How the hell do you not pull a vacuum on it while running right now?

My fuel cell has a rollover valve and then 1/2" vent line. It's not as hot here as Texas, but I have never lost any appreciable amount of fuel from evaporation. My buggy sits months at a time and the fuel is fine. I think you will be ok.

Later,
Jason
 
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