ATTN: Aux tank owners

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Jan 25, 2008
I'm still having issues with suction and pressure in my aux tank - the gas feed is fine - the only issue is how to let the thing breathe...currently i have an air line connected to a breather pipe at the top of the aux tank with one of the air lines leading to the OEM fuel separator...fuel gauge is saying its half full [which it is] yet i 'run out' of gas as the pump can't pull it out due to the pressure...


what if i just put an axle-style-breather tip on some 1/4" hose...but then i would have evaporation issues and an outside gas smell....
+1 on checking for (inward) vented gas caps. They should be letting the air into the tank to prevent a vacuum buildup.

Edit: if you ever need to replace your gas cap make sure you're getting the correct kind. I think newer cars have completely sealed gas caps.
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Take a few pics of it and post them. :) Maybe we can figure it out by looking

When you 'run out' and open the gas cap, I suspect it'll sound like it's drawing air into the tank (relieving the vacuum). Is that true?
ill take a couple pics in a few hours when i get home....i should have mentioned that the aux tank is filled through the OEM filler tube/gas cap...i welded on a pipe just after the cap - so to fill the oem tank i just do as normal - to fill the aux tank - i have to angle the pump into the pipe for the aux tank...i did hear a little vacuum hiss the other day when i discovered the problem - but surely the oem tank needs to be vented in a similar fashion? anyway - as far as i know ... the gas cap is oem...
Can you post pics of the filler setup? I want to do the same thing. How did you run the filller tube? Thanks

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