Charcoal Canister

After replacing all my fuel lines ('75 308/GT4) I decided to restore/replace the charcoal canister. After doing some research on the net I found that they should be replaced every 10 years and replacements for even common cars cost $60+ - I could imagine what a real replacement could cost for this car (Hint: even back in 1988 exact replacements were unavailable). I also found a few articles on rebuilding one, so I said, "What the heck?" Nothing as involved as MKE's project, but it does involve aquarium supplies and a $1.99 kitchen strainer. I don't want to waste space with a post nobody's interested in, so let me know on this thread if you are interested, and how many votes you think ought to decide the issue.

 

I finally got around to finishing this task. I hope it helps others out.

The charcoal canister is really a passive emission control device – it has a negligible effect on performance. What it does do is satisfy the requirement that no raw fuel be vented to the atmosphere. That meant no more breather holes in the gas cap, and no more venting the gas tank to atmosphere. But we all know altitude and temperature changes can change the pressure in the gas tank. Too much pressure and something goes POP. Too little (vacuum) and your fuel tank may collapse like a beer can. There is another thread on this site where this happened to a 348.

The activated charcoal in the canister absorbs gas fumes, which come in through the top tap; and gives them up when the engine is running through the bottom tap which is connected to the intake manifold. The manual says the canister should be replaced every 10 years, so at 35 years mine was a bit overdue.

I did some research on the web and found generic replacements (the original is unobtainable) cost $60+ and have a different configuration (three ports rather than 2); but I also ran across another article that said they were cheap and easy to rebuild, and included instructions and a tip: the activated charcoal is the same stuff used in aquarium filters. I ordered mine online from www.marinedepot.com The product number is

EV2210 ESV GRANULAR ACTIVATED CARBON 1LB 1 $11.99

Shipping was $7. (I have no affiliation blah… blah… blah)

The other replacement item I needed was a screen at the bottom of the filter. I checked several sources for Stainless Steel screen, and all required an outrageous shipping charge for overpriced screen. I bought a $1.99 strainer at the grocers and cut the screen out: perfect fit!

THE PROCEDURE

1) Cut the top off the canister. I used a Dremel with a diamond cutting blade. The top is about 3mm thick. Try to leave as much of the raised lip running around the top to provide a good glue surface for reassembly.

2) Here’s what you’ll find inside (activated charcoal not displayed)

3) El Cheapo stainless steel screen

4) El Cheapo Activated Carbon (charcoal)

5) Here’s the activated charcoal from the canister and from the aquarium supply: The stuff on the right is the original (or is it the stuff on the left? I can’t remember) as you can tell, they look pretty much the same.

5) Reassembly: Clean and dry all plastic pieces. I also rinsed the composition filter (looks like felt) and the foam filter in distilled water and dried them for a few days.

Fit the stainless steel screen over the standpipe in the canister, then place the composition (felt) filter over it.

Place the small plastic disburser over the standpipe.

Pour about ¾ liter of the new activated carbon into the canister. Leave about ¾ inch space at the top.

Insert the foam filter, the spider and the spring.

Glue the top back on, compressing the spring. This is the hardest part of the job. I tried several types of epoxy, then found JB Weld did the best job. The plastic is some kind of thermoplastic (ABS?) which melts when machined. If the JB Weld doesn’t hold I’m going to resort to heat welding (fusing) the top on. I’d show some pictures of this procedure, but they are ugly, and not befitting a prestigious website like this one.
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Right, you can spend $20 at McMaster-Carr or $1.99 at the grocery store for what you need. I was going to spend $60 on a GM carbon canister, cut it open and use the activated charcoal, but then I found the same stuff for $12 at the aquarium supplier. My mantra: "El Cheapo is OK, but watch out for El Junko."