Swapped Charcoal Canister Lines (1 Viewer)

[nmcbride89]

So, I installed an OEM gas cap because I was getting a slight fuel smell in my truck. The fuel smell actually got worse after doing this, and I started getting a "whoosh" when opening the new cap, so I figured it was my charcoal canister that could be the culprit.

I read on Mud that some folks were swapping the lines on the top of their CC to make this issue go away. I decided to try this, and the fuel smell has gone away and I am no longer getting the "whoosh".

My questions are 1) what is going on when you swap these lines on top of the CC and 2) is it okay to drive like this for a while? I have several other maintenance items to tend to in the immediate/near future, and the CFO of the house (aka my wife) is already tired of seeing parts constantly arrive in the mail and charges on the credit card.

 

[Output Shaft]

The port on the cc that the tank vent normally connects to has a spring loaded check ball in it. It's purpose is to hinder evaporation of the gas in the tank by keeping positive pressure on the tank vapors ...thereby reducing evaporative emissions. At a certain low pressure, the check valve is supposed to bleed the tank vapors to the charcoal.

As decades go by, the check valve malfunctions and sticks and pressure builds up in the tank higher than recommended. The whole FJ60/62 Toyota gas tank recall fiasco was caused by this malfunctioning check valve in the cc.... over pressurizing the tank... which caused tanks to split seams.

The other port on the cc doesn't have a check valve. It breathes freely through the cc.

The only "issue" that happens when swapping hoses is that the gas in the tank can evaporate a little faster, since there is no longer any positive vapor pressure, and the EVAP purge into the intake manifold will no longer occur because of the check valve now on that hose.

The A/F mixture of the engine was calibrated to account for the EVAP injection system, so when EVAP is disconnected, the engine will run slightly richer than before... Perhaps at the very slight hit of a little lower mpg.

But swapping cc hoses won't hurt anything.

 

[slacker24-7]

I've been running mine swapped for several years with no issues

 

[MiyamotoMusashi]

I did it on my 62 a few months ago. Was having the pressure in the tank issue. I haven't noticed any obvious changes in performance or MPG. I like it.

 

[fruitjack]

my tank always made the swoosh when i took off the cap; today i swapped the lines (i've got an FJ62, EFI) but i noticed there was still a (tinier but noticeable) swoosh. this happened both after i drove it a few miles and after i let it sit in the driveway for like an hour. is some sort of pressure build up OK or expected anyhow (just due to the fact that gas will evaporate a bit when hot) or could there be something further amiss (say faulty VCV)

 

[OSS]

The tank is supposed to pressurize a little. It’s normally controlled by the check valve in the canister. If it didn’t, vapors would always eek out the canister when the outside temperature rose.
The purpose of the canister is to reduce gas fumes evaporating into the air which contributes to air pollution. Some back pressure in the tank is necessary for that.