Hello all,

Where does this line go? It runs from the fuel tank vapor valves but when I bought the truck nothing was plugged into it. Now that I'm rebuilding the truck I'm wondering where to plug this into.

 

That's the evaporative emissions system. There should be a charcoal canister mounted on the passenger frame rail, '78 I believe will be rectangular, earlier ones were round. From the canister there was a 3/4" corrugated cardboard hose that ran to the side of the air filter housing.
I'll see if I can dig up an illustration of the '78 system.

 

Thanks again Mike! I had a round canister under the driver side fender cowl. I thought the previous owner was a coffee lover and hid his stash there.

If you can find the diagrams that would help. I'll try and search for them on the internet too. I guess I need to move my canister to the passenger side. How long do those canisters last, do you know?

 

Hmm, looks like I have to correct myself. According to the parts catalog the rectangular canisters were California and Canada, everyone else still used the round canister in '78.
Click on the .pdf link to view the illustartion from the Ford parts catalog.

 

The canister on the drivers side was probably the vacuum reservior for the A/C.
Here's what the charcoal canister looks like. AFAIK they pretty much last forever. I had one rust out though.
The small hose to the right in the picture goes to the fuel tank, the center is a breather/vent, the nipple to the left goes to the air filter.

 

Great, thanks!

The canister looks a little different in the diagram than mine does. Mine honestly looks like a coffee can. I may look for a new one on NPD or Dennis Carpenter to make sure I have the right components.

Last question. Do I even need this system? I live in SC and we don't have emissions tests. Does this system effect performance?

 

That picture helps. I definitely did not have one of those. I'll look one up.

You're build is looking great by the way. I enjoyed reading your heater box post. I decided to finish rebuilding the heater portion of mine and selling it on ebay or something. However the new heater core I ordered wouldn't fit as the lines were in a different place. I'm going to try and find the correct one tomorrow.

 

If the canister looks like a coffee can then that's a vacuum reservior not the charcoal canister.
Carpenter or LMC won't have them, possibly some obsolete suppliers might, I'd have to search, salvage yard or I see them occasionally on e-bay.
Do you "need" them? Not really. The only function of the evaporative emission control system was to route the gasoline vapor from the fuel tank into the charcoal canister then up to the air filter housing where it would be sucked into the engine and burned rather than dumping the raw vapor into the atmosphere where it would contribute to air pollution.

 

Thanks Mike. I'll poke around. Have a great night!

 

I you decide to not run the charcoal canister, DO NOT cap or plug the line that goes to the fuel tank. That's how the tank vents itself.
If you do cap the vent line, you'll need to switch the fuel filler cap from the non-vented style to vented or else you'll have fuel supply problems that will drive you nuts trying to find......or a collapsed fuel tank.

 

Ouch! Thanks for the tip. I think I'll keep the system since I don't want those issues and I already ran the stainless steel lines.

 

Double post!!

 

Whoa! You are confusing the "coffee can" sized vacuum cannister with the Evap/Em cannister. Vacuum cannister usually located on the left fender inner apron, just in front of the firewall.

Evap/Em cannister looks totally different, is located on the right inner frame rail, usually below the alternator.

Evap/Em: Unleaded fuel, non vented fuel cap. Originally the fuel filler tube had a restrictor in it that served two purposes.

The Evap/Em non vented fuel caps have 4 prongs on them, 2 above, 2 below 180 degrees apart. The restrictor had a provision for the 2 lower prongs.

Back then, there were two different diameters of filling station nozzles. The leaded fuel nozzle was larger in diameter, would not fit into the restricted fuel filler tube.

If you have dual fuel tanks, you have two fuel vapor valves, one in each tank, two restricted fuel filler tubes and two non vented fuel caps.

When catalytic converters were introduced, some peeps knocked the restrictors out of the tubes so they could use leaded gas that was cheaper than unleaded gas.

But guess what? They didn't realize that the lead in the gas melted the charcoal inside the converter, shoving it into the muffler.

It wasn't too long before their vehicles sounded like vacuum cleaners headin' on down the road. And it wasn't too long before their vehicles quit along the road. Muffler plugged solid with melted charcoal.

 

I had a friend that happened to not too long ago. He wanted to make his family mini van go a little faster so he dumped a bottle of that high octane, and yes, lead added, additive in his fuel. Well, it only took two tanks fulls of fuel with that stuff in it to make his mini van NO GO no more... He said just before it stopped running it started making this rattling noise HAAAAA. All the cats innards was rattling around in the muffler. It didn't want to start very well, and when it did, when you put your foot to the floor, it would die. If I knew he was doing this to his minivan I would have tried to warn him. Oh well.
Fritz

 

Thanks Bill! This is great information and I'll keep it in mind as I finish up my fuel system.