aztoyman

99 4Runner 3.4. I would like to get a better understanding of what goes on in the Evap charcoal canister.

One port to vent tank.

One port to (PWM) VSV to manifold vacuum.

One port to air filter housing.

One port has a line that just goes into the frame rail.

Two small ports that go to a Vacuum valve and off that vacuum valve a hose going to the vapor pressure sensor.

I understand the ECM controls the VSV to regulate vacuum in the canister allowing fumes from the tank and air box to be burned in the engine.

I would imagine the vapor press sensor would limit too much vacuum or press to build?

How or what does the other vacuum valve with the 2 small lines do?

What does the line into the frame rail do?

aztoyman

The truck reeks of stale fuel when driving. No leaks, smell is at the charcoal canister. No smell while idling, no codes, gas cap tested good at emissions.

Once up to operating temp, VSV pulsates and allows vacuum to canister. Not sure what the other components do. No obvious cracks in canister but, seems to be source of the smell. Saturated?

Very expensive and want to make sure it is problem before replacing it. This is in my son's 4Runner and he doesn't have a big budget.

aztoyman

Nobody? I know there are some real sharp Toyota techs on this forum.

Most of the searching I have done seems to be for the under body evap canister.

I'm going to loan my charcoal canister to my son to see if it fixes it. Parts changing is not my usual style of repair.

I'd like a better understanding of how it works so I could actually "troubleshoot".

YotaWoRx

The line going to the frame rail is a drain. Are the vacuum lines hooked up correctly? Was the tank overfilled at some point? Are the fuel return and vent lines attached to the canister correctly? Is the solenoid to allow the canister to purge operating?