Charcoal Canister replacement

[71CHEVYSHORTBED402]

I'm staring at my canister, which is no good. If they're good the charcoal should feel loose when you shake the canister. Can't speak for all, but the 71 truck canister does not open (WTH were they "thinking", they would last forever?).....

I believe the alternatives are 1. Cut the canister open to replace the charcoal, and glue it back together. 2. Take it off, use a vented gas cap and leave the line for the gas tank open with a breather on the end See edit.

My questions are:

1. Are there any other practical alternatives?

2. Have you been able to locate a reproduction that fits and has the correct hose nipples? Note: There are three nipples. One from the gas tank, one from the carb and one from a PCV valve.

Incidentally: Appears replacing the canister with NOS or an OEM that's still good is next to impossible.

Edit: Well, once upon a time I had breather cap on the end of the line coming from the tank. I just got underneath and it's no longer this way. There are three lines for the fuel pump. 1. Gas in from the tank. 2. The air line from the gas tank. 3. Gas to the carb. I'm not mechanical enough to know what this is all about, I can only say it works.

[mike16]

will the part number for the truck interchange with any other application.

when I run into problems like this I go to corvette vendors, high performance=heavy duty

corvette vendors have some really nice under hood detailing stuff and usually of pretty high quality. I solicit from those vendors who advertise in the NCRS publications. They dont last long in that community if thier pushing scrap.

I recall LMC selling that part through thier catolog several years back. I was replacing hoses on my 72 and thought to replace that canister as well but mine was good then and is still good now.

there is also a small filter element located in the botom of that canister, it is serviced by replacement on an as needed basis.

GM never intended that the part last for ever, It was required by law to maintain emmissions for the duration of the warrenty period. with enough spares on the shelf to keep customers trucks up and running.

can you run alcohol through it to clean the carbon particulate. In labratory envirionments the carbon is rinsed and heated to very high temps, then reused. not practical with plastic canisters but something to think about if you get that far.

you may consider eliminating it but keep in mind that its usefull for emmission purposes, does NOT reduce horse power and improves gas milage by about 1 to 2 mpg's

[71CHEVYSHORTBED402]

1-2 mpg is a 10-20% increase. At the very bottom there's what appears as basic insulation. Remove that and you can see some type of element, which you can't get to. It's orange and looks to be in good condition. Alcohol huh? I wonder if it would harm that element.

[mike16]

The element is exposed to heat fuel and other chemicals, mine lasted 38 years, alcohol is s pretty tame stuff compared to that and is not directly exposed to the element.

The alcohol is used to rinse /flush out the charcoal particulate, the element is replacable, I supose you could clean the element in alcohol. but thats a bit extream.

Have you restored Corvettes to NCRS standards in the past? I thought for a moment I recognised some of the symptoms.

[mike16]

Originally Posted by 71CHEVYSHORTBED402

1-2 mpg is a 10-20% increase. At the very bottom there's what appears as basic insulation. Remove that and you can see some type of element, which you can't get to. It's orange and looks to be in good condition. Alcohol huh? I wonder if it would harm that element.

only if you were drinking alot of it and hit the truck pretty hard on that corner when you wrecked itAnd believe me when I tell you I have seen a few in wrecking yards like that.

The element is what is replacable, the other guts are not typically replacable and not accessable because owners might fiddle with it, and as an emmssion device that would have been a no no.

the 1-2 mpg improvement comes in warmer climates and higher altitudes. at sea level and colder temps, evaporation is not so much an issue.

[Jason Banks]

Check out this thread for possible replacement part numbers:

http://67-72chevytrucks.com/vboard/s...d.php?t=569115

[Jason Banks]

Here's one...

http://www.rarenosparts.com/70-77-CO...OS_p_1591.html

[71CHEVYSHORTBED402]

Originally Posted by mike16

only if you were drinking alot of it and hit the truck pretty hard on that corner when you wrecked itAnd believe me when I tell you I have seen a few in wrecking yards like that.

The element is what is replacable, the other guts are not typically replacable and not accessable because owners might fiddle with it, and as an emmssion device that would have been a no no.

the 1-2 mpg improvement comes in warmer climates and higher altitudes. at sea level and colder temps, evaporation is not so much an issue.

Maybe I don't know what the element is. Here's are the parts I can get to (see two links for pictures).

1. The top pops off, spring and washer for it. Some type of diaphragm valve?

2. Bottom: Insulation, then a plastic screen, that cannot be removed, as it's part of the mold. Beyond the screen is an orange piece foam which I believe is "the element".

https://photos.google.com/photo/AF1Q...bSb0F-F9gQ64mU

https://photos.google.com/photo/AF1Q...1HsEWlI_ffviD7

[71CHEVYSHORTBED402]

Originally Posted by Jason Banks

Here's one...

http://www.rarenosparts.com/70-77-CO...OS_p_1591.html

Interesting, expensive too. Slightly different than mine but would likely work. I wonder what the "CARB BOWL" on RH top is for? The original 71 part does not have this.

These canisters seem to pop up for Corvettes often. They hold them pretty close I'd say.

[71CHEVYSHORTBED402]

With some research, I found you can find replacement elements/filters fairly easily. The catch is for at least the canister "type" on my 71 truck, you cannot get to the element without cutting it open.

GM shows 7021739 "Filter Assy. with drain cap fuel vapor canister". Going by what's available for this part on the market, it looks to be a screw or snap on for the bottom only, for only some of the originals (same part number with at least two different set ups). Here's one of those bottoms.... http://www.ebay.com/itm/New-AC-Delco...-/351167255821

I sent an email for that $200 piece, which isn't a true replacement part. I'm not necessarily interested in blowing $200, but would like to see if the dimensions are common. It also has this "CARB BOWL" part. Can't tell what it's used for, but I asked. I see the CARB BOWL on a lot of originals and most all replacements. The CARB BOWL portion was not a component for the original canisters for the 71. I can only say my carb. has two nipples capped, both near the fuel line connect (Quadrajet).

[picklito]

I'm about to cross this bridge on my 70, but haven't looked into options/availability yet. I do think the canister is a good idea, though, as it's a relatively safe and effective way of venting a gas tank, helps prevent vapor loss to the atmosphere, and it really doesn't hurt anything. So I'll be watching...

[71CHEVYSHORTBED402]

Digging deeper, the CARB BOWL found on many of these canisters (probably not original 71) attaches to carb bowl vent. The connection is different than the others on some of these, and I can't tell how it works. An example of this canister type is: http://www.rarenosparts.com/70-77-CO...OS_p_1591.html

Two questions for our emissions experts:

1. Seems these canisters are fairly straight forward and interchangeable. Other than the various ports, and assuming they're the same size and fit, can you think of a reason why they wouldn't work between applications?

2. Any reason not to buy a canister with a CARB BOWL connect and not connect it?

If they're interchangeable, this may be one of those parts an OEM search isn't worth the effort. Like any other filter they wear out with use. You can still get a Rochester or AC Delco. Here's one example. I've left a question about the markings for each line. From what I can tell, for $57 you get a brand new one that's set up for the same components, only the lines are reversed. The ports may be different sizes (could be a problem). Amazon.com: ACDelco 215-159 GM Original Equipment...

[picklito]

No emissions expert, but I did jog my memory with a little reading on this since I'm doing it, too.

Our sources of vapors are 1) fuel in the tank, 2) fuel in the bowl. So a "vent" line from each of these is routed to the charcoal canister. The charcoal canister is a semi-closed system (see * below) and the vapors from these fuel sources reach a dead-end in this canister while the vehicle is sitting. This keeps the fuels from just evaporating into the atmosphere. Think of this as easily avoidable pollution... and to a small extent keeps your gas in your tank so you can drive it! Guys... this is good for Momma Earth. Really.

Now you decide to drive and you start your engine. Those vapors are sucked from the canister into the combustion process. To do this there is usually some version of two other lines: 1) a vacuum source - such as a T from PCV manifold vacuum to suck the vapors into the intake manifold and burn them, 2) a second source of vacuum to open a valve on the canister so that #1 is open and sucking in vapors (*remember that I said it was a semi-closed system).

So, ya, you could use a generic canister and not connect the carb bowl line.

[71CHEVYSHORTBED402]

Great info. Picklito. The vapor storage/pull system finally clicked, but not knowing much about carbs and vacuums, I wasn't sure how the vacuum system operates. You saved me some research.........That second vacuum connects to a vacuum on the carb. Might explain why it says "carb".....Ha!.

I'm not surprised they're somewhat interchangeable. Only mystery are dimensions, but I bet the canisters on many are 5" diameter, and 5.75" top to bottom.

[In The Ten Ring]

Did anyone ever find a good direct replacement for our trucks? Mine is a 1972 and I want to replace the canister.