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Gas tank vent

rooster57

rooster57

Member
I am using a roundy round tank on my car the cap is vented IE air will go in but not out . I noticed this weekund she would swell up like a fat gal at the Furrs buffet. What would be a solution for a vent . My neighbor suggested a bulkhead fitting in the top and vent hardline just throught the bed floor with a small filter on the end.The existing fitting is the fuel line just not installed in this pic. And no the solution isnt to get a tank from RPM.:)
 
Hi Rooster, I like the thought of having a fuel cell that is rupture resistant and retains fuel even when punctured. Especially if hit from the rear. My question is if the fuel is being drawn from the tank and you have a vent that is one way into the tank, why is the tank swelling? Shouldn't it be contracting? NO, that would only happen if the vent in the cap became plugged. Unless it is a feature that pressurizes the tank so you always have fuel flow. I would call the manufacturer. Or call Ron. Also see what sort of protective frame you could make for both the tank and the battery. Anchor them both. Like the roundy round cars.
Just thinking, if the gas is heating up (either by outside temp. or perhaps sunlight) and expanding maybe thats the problem. How do desert racers cope with your problem?
Call the manufacturer.

Hope I helped, John

P.S. CCR makes a nice "cage" that fits in a 20 in. bed and mounts both tank and batt.
Just something to look at for ideas.
 
Rooster, I know you already have plans for a strap to hold things in place, this is not your first dance.. and yes it is the heat from outside temp. that swells the tank, I know you already know this too.. I carry a spare 2 1/2 gal, tank/can/plastic in my Elk, just in case, and in warm weather it gets pretty round.. hehe If the tank is full it can be a problem with overflow, you could (if you remember) crack the cap when it is sitting in warm weather to relieve the pressure problem, but remembering to tighten it each time before driving, guess you could leave the bed cover up, that would remind you.. I have a plastic plug in the top of my fuel tank, with a pin hole drilled in it, but if the tank is too full, it can and will make a bit of a mess even then... If we could go up, (with a vent) it would not be a problem, but the tank is already up there. Looks like a nice tank... Good Luck with whatever you decide on... :)
 
i usually use some braided line, or aluminum tubing and put a loop in it, and run it out the bottom..


i think theres a check ball vent you can get also.. check and see what aeroquips got, seems like i used one before..

vbpgimage.php
 
Yes it is straped down and the battery as well. Ted makes a good point will the pressure push the fuel out on the ground .I think i will duplicate what i have with some type of small filter on the end out of site to keep debris out. I will report back with pics . Thanks Guys
 
rooster57 said:
Yes it is straped down and the battery as well. Ted makes a good point will the pressure push the fuel out on the ground .I think i will duplicate what i have with some type of small filter on the end out of site to keep debris out. I will report back with pics . Thanks Guys
Click to expand...
I made a big mistake once and filled my tank full, then I just parked it in the alley at home, well it got warm (it all expanded) and about a full gallon leaked out, so glad my bed floor is not sealed tight, as it would have been holding all that gas, not a good thing, and I may not have noticed that it leaked that much either. Next time, I think I will make a tank that is under my floor boards of the body, keep it low so a good (safe/up higher, away from exhaust) vent can be made... ;)
 
you might get some to come out, but the fuel hits the loop and the vertical part of the loop makes it harder for the fuel to pass....



surely you guys have been on a dirt bike with the vent hose that hangs off the gas cap, this work the same way...
 
"And no the solution isnt to get a tank from RPM." :sad:

Yea a little hole with a tube in the top and a loop or 2 should do the trick.
At least when you drill a hole in that plastic you won't have to worry about a spark.
 
RPM said:
"And no the solution isnt to get a tank from RPM." :sad:

Yea a little hole with a tube in the top and a loop or 2 should do the trick.
At least when you drill a hole in that plastic you won't have to worry about a spark.
Click to expand...

I guess the loop thing would work as long as it's not attached to a tube that goes into the tank. I made the mistake of using a sprint car-type rollover vent and valve. When I would fill the tank it would begin to siphon fuel from the tank. A loop in that configuration would have acted like a sink trap and held fuel cutting off the air flow back into the tank just like a sink trap holds back the swamp gases.
 
"i usually use some braided line, or aluminum tubing and put a loop in it, and run it out the bottom.. "

I'm going to use this one. Thanks Brucer.
 
RPM what do you do on your tanks. The construction of the tank is im-materal i would think the pressure will push it out of a metal tank as well Right?? ARG
 
The loop needs to be 100% above the tank. I have a height issue.
 
rooster57 said:
RPM what do you do on your tanks. The construction of the tank is im-materal i would think the pressure will push it out of a metal tank as well Right?? ARG
Click to expand...

Just a guess here but I would think that the pressure in a properly vented tank would be balanced. The vent lets air in to displace the vacuum created as the fuel is pumped out. It should also relieve pressure that is built up through temperature variations. But I was wrong once before.
 
I'm sure my cap was vented one way. I had the aircraft style cap. I drilled out the vent hole with a very small bit and finally stopped my siphoning problem.
 
speedway sells a little gas tank vent with a check in it , so if the car was upside down the gas wouldnt come out of it , i was going to put one of these in my tank ,
 
That's probably the one I had. The tube extends down into the tank a few inches and as soon as I put the gas cap back on the gas would start to siphon through that tube. When I drilled out the vent in my cap that problem went away.
 
Why would a breather or vent tube extend "a few inches" down into a gas tank. Meaning that the tube would be partially immersed in fluid (gas) when the tank is full. Of course it's going to siphon. A breather should be surface only, not in the fluid.

John
 
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