I have a 1979 F150 4x4 with a 300 6cy 4sp Np435 and a np203 transfer. The charcol canister under the battery has a hose cut off with a screw in it and I would like to reconnect it to the original location. There are three vacuum hoses that come off the blue cap on the canister, one goes to the top front of the carb, the other connects to a tee that runs a line to the EGR valve and the third line is the one not connected with a screw in it, it is the bigger sized vacuum line of the three. Then under neath these three is a line from the fuel tank that plugs into the canister. Any one out there have a truck like mine that can help.

 

The large line should run to the bowl vent on the carb

 

The larger line does go to the bowl vent on the front of the carb. I was wrong the vacuum line that is cut and pluged is not the larger of the three, its about the size of the vacuum line that is attached to the EGR. So what does this go to ?

 

I've posted about this very subject years ago in the 73-79 forum. IIRC there are four ports on the do dad that sits on top of the canister. The top one (the big one) is for the carb bowl vent). The lower one is for the gas tank vent. The two in the middle is where the magic happens. One should hold vacuum the other will not when the other has a vacuum applied. The do dad is a valve of sorts. One of the ports is made to sense vacuum, the other of the two opens allowing the canister to be purged when the sensing port is under vacuum. I hope this makes sense. So where to connect them? The sensing (or signal) port should be T'd into the line that also opens up the EGR and Bypas valve for the air pump. The source port (or what actually purges the vapors out of the canister) is usually connected to the smaller port of the PCV valve. There is usually a restictor or small orfice that is placed in the source line to keep the vacuum loss to the PCV minimal. I know this because I had to resurrect my entire emissions system from the dead about four years ago to get my 79 to pass CA SMOG. It too has a L6. I think I can fish up the vacuum diagrams for a '78, but I need you calibration # to dig for it. My site has some information...even the '79 diagrams should get you in the right direction just to get your canister in shape.
tetraruby300.freewebsitehosting.com
Cheers.

 

I don't believe I have a air pump. Above the altenator is a braket with holes that looks like something was mounted to it, it this where the air pump goes? Where can I get one? A bypass valve, I have no idea what this is or looks like. Any pictures would be great, I would really like to get this solved and back to original stock conditon, thanks oem78