72 Charcoal canister confusion and questions

[Gary S.]

While I await my new gas tank and vapor separator, I am replacing the fuel and vapor hoses from the tank to the hard lines and to the carb. I guess I really don't understand how the charcoal canister is plumbed. In the 72 AIM page M213, the bottom figure shows the vapor line going to the canister but the drawing is vague enough that I don't see how the vapor line from the separator connects to the canister. The bottom figure also shows one nipple at the top which I am guessing is the line from the vapor separator? The upper figure View A shows hose #12 but I assume that is one of the hoses to the carb or is this the line from the fuel tank? Then, when you turn to AIM page M215 it shows the canister in better detail, showing three nipples on top, two of which go to the carb. And one assumes that the other one is the one from the vapor separator. Correct?

Regardless, I can barely see the canister from the fender and I am doubtful that crawling under the car will give me a better view. Can anyone clarify this? Also, if I choose to work on this canister is there really any way to remove it easily and other than using feel only? That is a tight fit! Final question, on AIM M 213 the canister appears to be a two piece affair with item 8 being the canister and item 7 being the drain cap. I can't see enough detail but is this a serviceable item? My reading from the search function shows that these usually last a very long time without any replacement components.

[Patrick H.]

Re: 72 Charcoal canister confusion and questions

Gary, you can remove it most easily from below by taking out the triangular metal shield between the wheel well and the frame. You can also remove the "gill" on your car to see all the connections right there. Inspecting from these 3 directions is probably the easiest way to see how it is plumbed.

[Alan S.]

Re: 72 Charcoal canister confusion and questions

Hi Gary,
If you remove the left side's egg-crate grill you'll have good access to the canister.
There are 4 hoses on the canister. 3 at the top, and 1 on the bottom which is a drain line. The bottom cap is removable since there's a pancake filter that can be changed.
The upper surface of the canister has 3 nipples. Each is identified so that you'll know which hose goes where. 1 FROM the fuel separator on the tank, and 2 run TO the carburetor.
Regards,
Alan

Added: Sorry, Patrick posted while I was loading the pictures.

The canister and it's mounting bracket laying on it's side. Notice what I believe to be a Julian date stamp too. (363)
The top showing the 3 nipples and their labels.
The removable bottom and the drain hose.

[Gary S.]

Re: 72 Charcoal canister confusion and questions

Perfect description Patrick and Alan and perfect pictures too, Alan. Of course, you made me go back into the AIM to see how the egg crates come off.

The AIM is a wonderful tool but sometimes the diagrams leave a wee bit out. The photos are perfect in that regard. Tomorrow the egg crate comes out and I look at the canister. Of course, no vacuum work can be done until the gas tank is back in.

[Terry M.]

[Gary S.]

Re: 72 Charcoal canister confusion and questions

Thanks Terry. I learn something new every day. I assumed incorrectly that each vendor copied an original AIM from GM or, at worst, copied a copy. I almost put down the UPC X, Sheet info but assumed that a page number was a page number.

The photos that are provided answered every question I have. Once my car is running, I intend to check vacuum sources and leaks and the canister was one of those that I needed to check. Of course, with replacement fuel hoses going in, I hope to eliminate one potential source of leaks as well as negate a safety issue with old(er) hoses.

[Gary S.]

Re: 72 Charcoal canister confusion and questions

here are the photos

[Alan S.]

Re: 72 Charcoal canister confusion and questions

Hi Gary,
Is the piece of hose on the bottom drain nipple quite thin walled compared to the other vacuum and fuel hoses on your car?
Regards,
Alan

[Gary S.]

Re: 72 Charcoal canister confusion and questions

Alan,
Now you stumped me. My canister drain nipple doesn't have anything attached to it. I just have the three hoses as described at the top of the canister. Does your canister have a hose on the drain?

[Alan S.]

Re: 72 Charcoal canister confusion and questions

Hi Gary,
I was looking at your last picture and saw what I though was the drain hose; I guess it's the nipple.
Yes, there was a piece of hose/tubbing with a spring clamp on the drain line. On my 71 it's about 5" long and quite thin walled. It's unlike any other hose/tubing on the car. That's why I was curious about yours.
You can see it pretty well in the third picture I posted.
The hose diverts any seepage beyond the rear edge of the splash shield.
Regards,
alan

[Gary S.]

Re: 72 Charcoal canister confusion and questions

No, that is only the nipple and it shows no sign of ever being clamped and has some surface dirt inside the mouth.

[Alan S.]

Re: 72 Charcoal canister confusion and questions

Hi Gary,
The 71 Aim shows the hose (item #12) and clamp (item#11) in UPC 8, Sheet B5.
Maybe the use of the hose was stopped?
Regards,
Alan

[Gary S.]

Re: 72 Charcoal canister confusion and questions

Hmm, my UPC 8 sheet B5 shows the canister and item 12 is a hose but it's coming off of the top and the removable cap on the bottom is item 7 without any hose. Interesting. Ok, I pulled out an old 71 AIM and it shows the hose and clamp whereas my 72 shows an empty nipple.

[James B.]

Re: 72 Charcoal canister confusion and questions

Hmm, my UPC 8 sheet B5 shows the canister and item 12 is a hose but it's coming off of the top and the removable cap on the bottom is item 7 without any hose. Interesting. Ok, I pulled out an old 71 AIM and it shows the hose and clamp whereas my 72 shows an empty nipple.

When I restored the charcoal canister assembly for my '72 back in the mid 80's, I too didn't see any signs of a drain hose and clamp ever being installed.