Yes, that hard line goes down the pass side frame rail to the tank or tanks. It's the vent line that vent's the tanks. It is supposed to have a rubber line hooked to it, leading to the charcoal canister, which is a square black plastic box mounted down low on the frame. I think it's under the battery on these trucks, but check to make sure.

 

That metal line dose run down the ri G ht frame rail to the rear cab cross member where it crosses over to the left rail and hooks to the tank(s).

Also note there will be 2 charcoal canisters if you have dual tanks. And yes kind of under the battery.
Dave ----

 

Something like this, that's the battery above it.

 

Uhhh… I don’t recall seeing any box type item under the battery, but I’ll check. If the charcoal canister is under the wheel well and square… what is this round thing next to the solenoid just aft of the battery?




it looks like cheap little tin can with a line going into the middle of it..

 

That tin can sometimes called a juice can is a vacuum reservoir for the HVAC system.
I take it you have AC?
That tin can likes to rust out and cause vacuum leak.
Dave ----

 

I never realized or thought about it till your answer above. I had to go look but sure enough, a plain heater system was cables only, no vacuum. Learn something new everyday.

 

Oh I know all about cables and no cables with AC and non-AC trucks remember I am the crazy one that swapped firewalls so I could have AC

My truck came from the factory with out AC so it had the 2 cables/
Parts truck had AC and the vacuum can so every thing from the parts truck even the firewall was swapped over.

I also said about the can rusting as mine had pin holes on the bottom side, guess from water sitting in it?
I pulled the bracket off the can and used fiber glass rosin and coated the can then painted it black put the bracket back on and bolted it in the truck.

I dont remember how I found it was leaking?
I may of have a fast idle and started pulling vacuum hoses and when that hose was pulled and plugged the idle lowered?
I then might have sprayed around the can with carb cleaner and the idle changed so I guess I pulled it and looked it over and found the pin holes?

Another vacuum leak I had was the charcoal canisters.
Because i was missing some of the smog stuff like canister solenoid I ran vacuum to the PCV like the under hood sticker showed with out the solenoid.
Again have a vacuum leak and could not adjust the idle mix screw and traced it back to the hose on the PCV was pulling to much vacuum thru the canisters.
I took the smallest Holley jet I had the stuck it in the hose and this helped but I think it is still to big a jet / vacuum leak but the truck runs good so I have not messed with it for years now LOL
Dave ----

 

Ok, I looked everywhere and I can’t find the charcoal canister…. My battery basically sits right on the wheel well, on a metal bracket that is attached to the bottom of the plastic well. I traced the little hard line back and it actually splits then crosses over the frame to the driver side around the back of the cab… indicating there would only be 1 canister even though there are 2 tanks. I see what looks like a screw hole on the engine side of the wheel well in front of the little tube, maybe it was there?

 

Upon trouble shooting the gas tanks (detailed in “my 1st truck thread) I noticed a line hanging down by the diff… because the PO said the rear gas line was cut I assumed this was the cut line… but finding out it wasn’t, I now don’t know what this line is? I traced it and it seems to be open ended right where it mounts to the frame forward of the gas tank… clearly it is supposed to be hooked to something?

 

If you have 2 tanks then you should have 2 canister.
They should be bolted to the frame. Under the battery if not someone removed them.
Dave ----

 

That would be the rear axle vent hose and it dode go up where you see it to keep water out if you go thru deep water.
The other end fits a nipple where the brake lines tee and go to each wheel.
Dave ----

 

Thanks Dave, I guess that means it is probably the correct size and just came loose, and not cut. I’ll take it off, clean it, and put it back on where it is suppose to go.

 

That seems like a pretty small line for something non-pressurized, assuming the vent line isn’t. What are the repercussions of not having a charcoal canister? I plan on getting one if I can, but I don’t ever remember seeing a square one anywhere on the truck since I got it back in the day the first time. Is it safe to assume any canister will work and I don’t need a 1982 compatible?

 

The only think you may get is gas fumes smell.
The canister collects the vapor and when theotor is running pulls it in and burns it.
Other wise not a big deal not having it.
I would say any 80 to 86 and maybe later? Would work.
Again if you have 2 tanks you should have 2 canisters.
I will see if I can get a picture of my 2 when I get out of work if I can remember LOL
Dave ----

 

I am not sure about the 2 tanks, two canisters deal. My 1980 had two tanks and one canister. It had a tee in the vent line with one vent line like yours going forward with one canister. But I haven't researched it very much and possibly some trucks did have two canisters.