Another fuel tank vent post

[jaredts]

I know fuel tank vent questions usually start out with "I threw out my charcoal canister and now...".  I still have my charcoal canister and the vent from the tank is still hooked up to it.  The problem is that all of the other hoses were cut by some previous owner--awesome!  I also have my vacuum routing on the radiator support, but I don't think hooking all that back up is in the cards.  There is a large hose on the canister that is supposed to go to the air filter and it is spewing out vapors now that the weather is hot, not good.  If I cap that, will that create a vacuum and not allow the system to vent?  What's the minimum functional stuff I need here?  No emission testing on this truck.  I'm scared to hook any of this up to my carb. and have the charcoal come apart and destroy what's running good for me right now.

[jackjeckel757]

My "carb" hose on the canister was loose also, instead of plugging it into the carb I got a PCV valve with 2 ports on it and plugged it into that. The other port on the PCV goes to the usual carb port in the front.

[bake74]

My "carb" hose on the canister was loose also, instead of plugging it into the carb I got a PCV valve with 2 ports on it and plugged it into that. The other port on the PCV goes to the usual carb port in the front.

      Correct me if I am wrong, the charcoal canister is for venting fuel vapors into the intake to get burned.  The PCV valve is for positive crankcase ventilation.  Is this the best place to be putting this ?
      Someone with more knowledge on this system please enlighten me, Is the theory to add there and when the valve open they suck the vapor in, what happens when the exhaust valves open ?

[jaredts]

Best I can decipher from reading and looking at my emissions routing, the canister has:
1) fuel line vent valve
2) hose to air filter
3) carb bowl vent connection
4) purge connection
5) vacuum signal connection for purge valve
6) vacuum signal connection for carb vent valve

I'm not running a carb. with a vent, so that's two lines I don't need.  The line that should go to the air filter is the one spewing out vapors, which it would still do if it was hooked to the air filter.  Right or wrong, I have come to the conclusion that the air escaping through that line should be rid of most of their vapors by the charcoal, but isn't because my charcoal is saturated or broken down.  It is 30 years old and has been run for some time with no purge, so I am trying to figure out where to go from here.  Some have cut open their canisters and refilled with fresh charcoal.  Buying a new canister at $70 is an option but not the cheapest.  Buy a canister from a newer wrecked vehicle is an option as well.  Either way it has to be purged to remove the stored fuel or it builds up.  I'll report back.  Any experts can weigh in.  I don't want to just use a vented gas cap and cap off the vent because I don't want any more fumes than necessary.

[jackjeckel757]

My "carb" hose on the canister was loose also, instead of plugging it into the carb I got a PCV valve with 2 ports on it and plugged it into that. The other port on the PCV goes to the usual carb port in the front.

      Correct me if I am wrong, the charcoal canister is for venting fuel vapors into the intake to get burned.  The PCV valve is for positive crankcase ventilation.  Is this the best place to be putting this ?
      Someone with more knowledge on this system please enlighten me, Is the theory to add there and when the valve open they suck the vapor in, what happens when the exhaust valves open ?

I looked up many different ways to connect the charcoal canister and this was the easiest and yes a correct option to do. Another option for me would to be to get the Edelbrock or other carb that has a port for the canister hook up, but I did not want to replace my carb.

[jaredts]

I think the port on the carb. is just a vent for fuel evaporating from the bowl to go through the canister.  From the factory the purge is tee'd into the pcv line anyway.  The purge valve vacuum signal comes from ported vacuum and through a thermal switch so it only purges when the engine is warmed up and your throttle is not at idle.  Again I'm just working through this, so feel free to correct me.

[bake74]

My "carb" hose on the canister was loose also, instead of plugging it into the carb I got a PCV valve with 2 ports on it and plugged it into that. The other port on the PCV goes to the usual carb port in the front.

      Correct me if I am wrong, the charcoal canister is for venting fuel vapors into the intake to get burned.  The PCV valve is for positive crankcase ventilation.  Is this the best place to be putting this ?
      Someone with more knowledge on this system please enlighten me, Is the theory to add there and when the valve open they suck the vapor in, what happens when the exhaust valves open ?

I looked up many different ways to connect the charcoal canister and this was the easiest and yes a correct option to do. Another option for me would to be to get the Edelbrock or other carb that has a port for the canister hook up, but I did not want to replace my carb.

    I am always open to learning, will have to look up some info and read up on it.  Thanks for the answer.

[jackjeckel757]

Edelbrock makes a carb with a port specifically for the charcoal canister, I don't remember the model #, but it was a variation of the model 1406 I have, I just felt the PCV connection was easier.

[jackjeckel757]

Just looked it up, the Edelbrock 1400 carb has a port for the charcoal canister

[jaredts]

I haven't looked it up, but that connection should be a carb bowl vent, so those vapors get stored in the vapor canister.  The pcv line seems to be the typical place to purge, or suck those vapors back up.

[454Man]

Hey guys can we not just bypass the charcoal canister altogether and run the line straight to the carb? It is full of the vapors from the fuel tank anyhow. Idk I thought it be better for the engine to have more fuel vapor and gas

[jaredts]

If you don't use the vapor canister you have to plug the vapor line from the tank and use a vented gas cap.  When its hot out the vapors are expanding like crazy in the tank and will come out of the vented gas cap and you will smell gas.  The tank and carb. fuel bowl both have to be able to suck in air or blow out vapors as things expand and contract and as fuel is consumed it is replaced by air.  The only question is whether you just let the vapors along with the fire risk and nuisance smell escape or you allow the charcoal to absorb the vapors so you can "suck" them out of the canister later and burn them.  I just recently got my second gas tank working and on a hot day now the amount of smell and vapors are a bit much, and that's with the canister hooked to the tank vapor line.  I think my problem is that I am not hooked up properly to purge the vapors (suck them back up and burn them).