FUEL positive pressure issue

[garrett96]

I have searched threads and I cannot find any more ideas maybe someone can help me out here. I’ve seen people say they have a vacuum on their fuel tank but mine has positive pressure and so much that when I do put gas in it I can see vapors coming right back out the tiny vent holes along the side of where you fill it up. I’ve done changed the charcoal canister with the cheaper option VC120. That did help but if I tighten my gas cap and drive for 20 min or so it builds up so much positive pressure and it sends fuel straight to the canister, and it tries to stall out the engine. Lately I’ve been driving with the gas cap slightly on so air can escape. It drives fine but has a little trouble wanting to start but it will every time it just turns over a good few before it does

 

[AlYamoni]

I have searched threads and I cannot find any more ideas maybe someone can help me out here. I’ve seen people say they have a vacuum on their fuel tank but mine has positive pressure and so much that when I do put gas in it I can see vapors coming right back out the tiny vent holes along the side of where you fill it up. I’ve done changed the charcoal canister with the cheaper option VC120. That did help but if I tighten my gas cap and drive for 20 min or so it builds up so much positive pressure and it sends fuel straight to the canister, and it tries to stall out the engine. Lately I’ve been driving with the gas cap slightly on so air can escape. It drives fine but has a little trouble wanting to start but it will every time it just turns over a good few before it does

I'm having a similar issue with my '84 FJ60. What is your vehicle?

 

[Marvelicious]

Excessive fuel tank pressure

I've been chasing a fuel tank pressure issue for some time now. Last year I noticed when I drove up nearly 6k feet in less than 1 hour in July I had a bad gas smell and a whining from the drivers front. I opened the gas cap and it vented for (I kid you not) 10 minutes. Some time after that it...

forum.ih8mud.com

 

[garrett96]

I'm having a similar issue with my '84 FJ60. What is your vehicle?

97 lx450 4.5

 

[Malleus]

There are a lot of pieces in that puzzle.

Have you checked the TVV, VCV and check valve for the EVAP line?

There is also a tank breather line. You can access it after removing the middle seats, and peeling back the carpet.

These are from the 1997 LX450 FSM (RM515U). It should be in the Resources section. LMK if it's not.

 

[Malleus]

 

[garrett96]

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This helps I will definitely look into these, I have so far replaced VCV, EVAP CANISTER, FUEL REG, I will look into the rest where do you find these types of manuals

 

[BILT4ME]

Also replace your fuel cap.

 

[Malleus]

This helps I will definitely look into these, I have so far replaced VCV, EVAP CANISTER, FUEL REG, I will look into the rest where do you find these types of manuals

In the Resources section

 

[Rifleman]

Another issue that i feel exacerbates this fuel tank over pressure problem, is the fuel we have to buy that has ethanol mixed in it,