Charcoal Canister Setup Question 73 FJ40

Feb 28, 2022
Austin, TX
Hey all - 1973 FJ40 - looks like the original Charcoal Canister. I still need to trace the bottom hose but I'll assume it routes down to the bottom and is the breather. I'm more concerned about the line that is capped off.
  • I don't have a VSV and that missing VSV isn't connected to the intake manifold
  • I do have a heavy gas smell as I idle and drive. I feel sorry for the people behind me as I accelerate
The truck runs great. No back pressure when I open the gas cap. It just smells like fuel -- glad I don't have top or a doors. The rubber hoses are in OK shape, but I'll probably replace them since I have some and I've been making my way through the truck. I also have a newer charcoal canister I may try ... BUT I am pretty sure that capped line should be going somewhere.

I'd love to hear suggestions on what I should do to that outbound line from the canister ... and pics would also be awesome if they're available.


Sep 20, 2004
Definitely needs to be open, if the rest of the system is intact and the VSV is gone you could verify no vacuum leak where VSV manifold port is capped and route canister breather to air cleaner, however that will not provide a vacuum as per the VSV valve, it will just give the vented gas a place to go and will get introduced back into intake air.
If the VSV lets full vacuum thru when open you could route the canister vent to full time vacuum at capped port and see what happens, IMO I would NOT supply manifold vacuum to the canister vent unless someone who knows concurs. I know the PVC gets manifold vacuum but I don't know if the tank evap system should, I suspect thats what the VSV valve does, opens vacuum but also prevents pull thru with reduced vacuum or a trap of some sort.


Feb 2, 2002
No check valve? Did someone drill a hole in your fuel cap? The vapor pressure has to go somewhere.

I’d recommend starting at the fuel tank and seeing what you have for your EVAP system. I put some photos and link in the thread below.

The short answer is that line needs to be uncapped. The more correct answer is to verify what you have for the EVAP system as a whole and go from there. Currently my charcoal canister vents to the atmosphere thru a small filter under the hood. My wife notices no smell (other than “old car smell” of grease and oil). I’ve meant to plumb it into the intake, but never found the need.

The EVAP system was really misunderstood back in the day so lots of previous owners blocked them off.


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