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Old 03-29-2019, 05:24 AM   #1
Junior Member
Join Date: Feb 2019
Posts: 16
HELP!!Fuel Station Tank Venting

We purchased a 2019 in Oct 2018. Recently added, by Camping World, an ONAN generator, great add on. Question, has anyone experienced their auxiliary gas tank "popping" with expansion as the gas vaporizes in the tank? When I say "popping"(deflecting the metal/not sure if the tank is actually bulging) I mean loud enough to hear it 40'-50' away. Visual inspection of the tank doesn't look as if the tank is deforming. I've checked the gas cap venting valve and it appears to be working, put my mouth on it and blew through it, softly and reasonably hard. Obviously this is worrying as I don't need the tank deforming or worse bursting with pressure. Generator runs fine so I don't believe there is a vacuum or that it's not venting, it's somewhat confusing. When I do release the gas cap, slowly, it does vent a lot of vapor. Could the vent flappers in the cap be bad? I contacted Camping world and they assert the installation is correct and vent lines were installed appropriately. Could the cap be defective? Any other suggestions?

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Old 03-29-2019, 05:30 AM   #2
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Join Date: May 2017
Posts: 4,605
I've had multiple gas vehicles that have done the same thing over the years. Go to fill up and you could hear the hiss of air as you took off the cap. I just always accepted it as that's what happens with expansion and contraction. Not sure what to tell ya. Sorry.

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Old 03-29-2019, 08:46 PM   #3
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Join Date: Feb 2019
Posts: 16
Found the Problem

Well after couple of days looking, inspecting, calling and evaluating again, I found The problem. FAULTY gas cap. When you close the cap and it clicks, as described on the cap, the vent essentially closes. If I turn the cap back, counter clockwise, as if I'm removing the cap, until the first point of resistance, the vents reopen. I tested this process with the cap off. I spun the internal portion one direction, to the first indent. The vent was closed. I then returned the inner portion of the cap back to the opposite direction and the vent opened. Looks like a new cap is in order. Appreciate your though on the matter. Hope this helps someone else.
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fuel, tank, vent

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