Fresh air to fuel tank

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Kmix1999
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Fresh air to fuel tank

Post by Kmix1999 » Mon Dec 24, 2018 2:10 pm

Looking for some advice / help as this problem has me stumped. 1992 Legacy LS AWD (completely stock) with severe pressure build up in the fuel tank. I know the gas cap allows air to enter the tank through the built in one-way check valve. But how would excess pressure in the fuel tank escape? The only vent I can find from looking at diagrams are the vapor lines going from the top of the tank to the fuel separator, which then goes to the single line ending up at the charcoal canister in the engine compartment. This line to the charcoal canister has a rollover valve installed somewhere near the fuel tank which I suspect is blocked. I have not been able to find a picture of this rollover value but some older posts say it's mounted near the drivers side of the tank. I need to crawl under the vehicle and have a look. Also, I tried blowing compressed air through the larger "tank" hose at the charcoal canister and some air flows but not much. Sucking air through this line seems much easier then pushing.

Am I on the right track or way off? Any advice would be greatly appreciated.

Kmix1999
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Re: Fresh air to fuel tank

Post by Kmix1999 » Sat Dec 29, 2018 3:44 pm

Update: in case someone else has this problem. My high pressure in the fuel tank issue was indeed the rollover valve. After 27 years, if finally clogged/ blocked. Probably could have cleaned it but chose to install a new one instead. You could probably delete it too with 1/4 OD tubing, just don't roll the vehicle over.. haha. The valve is bolted to the body with a bracket. The left rear corner of the fuel tank near where the trailing arm attaches.

mike-tracy
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Re: Fresh air to fuel tank

Post by mike-tracy » Sat Dec 29, 2018 9:12 pm

Thanks for the update. I don't have huge buildup in my tank, but filling up with fuel is an exercise in frustration, and my car is only 21 years old.
1992 Legacy SS 5mt, build in progress

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