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Fuel tank building pressure

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Old 02-11-2017, 06:06 PM
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Fuel tank building pressure

Hello

My fuel tank seems to be building up pressure. When i open the gas tank cap it releases the pressure with lots of force. I am note sure if it originally had an emissions hole in the tank as i didn't change it myself. I know for sure we ordered one without the emissions hole because the guy who installed the tank told me to do so. Keep in mind, we swapped out the original 400m and original carb for a 460 and a 4bb carb. How would i go about figuring out why my tank is building pressure and how can i fix the problem. what do i need to trace and or figure out what it originally came with as far as emissions go

Thanks
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Old 02-12-2017, 09:51 AM
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I think it would still have some kind of vent on it, and that vent must be plugged up somehow. Gas evaporates quickly, the tanks got to be vented. If you don't have a charcoal canister for the EVAP system anymore I'd add one so you don't smell the gas on hot days.
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Old 02-15-2017, 05:45 PM
EDC8008 EDC8008 is offline
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It has to vent somewhere, if not these are the things that happen. There should be either on coming off the tank with the sending unit or fitted to the top side of the fill neck at the door. Newer vehicles will typically have a line going to the charcoal cannister.
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Old 02-16-2017, 12:21 PM
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something doesn't seem right. there is a separate hole with a hose going into the tank right beside the filler neck hole and hose. i believe this is the vent hose? i know for sure i don't have a EEC tank. the tank is completely sealed and not breathing when i put the gas tank cap on
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Old 02-16-2017, 05:33 PM
EDC8008 EDC8008 is offline
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Yes that would be the vent and it must be clear.
typically there should be a plastic fitting in the end to reduce water and dirt entering unless it originally went to a canister, so pull it and make sure it's clear.
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Old 02-19-2017, 08:41 AM
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Quote:
Originally Posted by papyjack View Post
something doesn't seem right. there is a separate hole with a hose going into the tank right beside the filler neck hole and hose. i believe this is the vent hose? i know for sure i don't have a EEC tank. the tank is completely sealed and not breathing when i put the gas tank cap on
That sounds like the hose that follows the fill pipe up and goes into the side of the fill tube. That hose is just for making it fill easier. The tank needs vented, either through that small hole on top of the tank with the roll over valve built in it with small tubing to cannister or needs a vented cap.
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Old 02-19-2017, 08:45 AM
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Old 02-19-2017, 08:49 AM
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This needs a grommet and fits into that top tank hole and vent hose attaches.
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Old 02-19-2017, 03:19 PM
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Evaporative Emission: Unleaded fuel, NON vented fuel cap, fuel vapor valve located at the top of the tank adjacent to the fuel sending unit.

Vapor line routes along the inside of the right frame rail to the charcoal canisdter, usually located below the alternator.
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