Vapor Canister Rebuild - A new how to

[nograin]

Having just rehabbed the charcoal canister in my waggy, I thought I'd do a write up. Eventually I'll hope to put it on my website and in the archives, but for now at least it will be here.

A few years ago Scotty wrote up how to adapt a later canister to work. But, that canister is now just about as hard to find as a correct one for an SJ. So its back to fixing 'em...

There's a good write up on repairing the canister by TWMattox starting on post #7 of "carbon in carb." Lots of good pictures and explanation there. So, I hope that to add to what he did and also clarify how it works.

The canisters changed over the years. The one I took apart is from an 1985 Waggy. The main body is off-white and has 4 ports on top including the one in the black cap. The ports are as follows:
- Fuel Tank Vent
- Purge line to PCV valve side port (constant manifold vacuum)
- Carburetor bowl vent (through vapor seperator & solenoid valve)
- Secondary purge signal from ported vacuum

The secondary purge line does not actually do any purging. All it does is provide a vacuum signal to a sealed rubber diagphram. On the other side is a manifold vacuum and a spring. When the throttle is opened, ported vacuum equals manifold vacuum and the spring lifts the seal allowing a more air to purge from the canister to the PCV valve connection.

I found nothing about the vapor canister, the solenoid valve, or vapor seperator in the MR 253. Did I just miss it?
Thanks to other members here and what Tom Collins has on his website, the 1981 and earlier FSM at least have some information. Did they just forget about the vapor emmissions controls in 1984!?

[nograin]

Opening the can

Part 1: Opening the Canister

Purge Valve
1 . Disconnect the lines and remove canister from engine bay. Note the bottom of the canister is wider than the top, so it won't just slide up and out of the clamp when loose.
2. Purge valve (says "Do Not Remove"). Carefully pry around the edge of the cap. There may have been an adhesive on the front on the two tabs around the nipple. It didn't hold to the cap to any degree worth mentioning.


3. Inside is a rubber diaphragm, and a spring with retainer. The diaphragm is special, so don't toss it even if holey.


Main Housing with Charcoal & Filter
1. Turn can over and remove the filter. Oops, I should have replaced this a little more frequently.


2. Place it on the side or whatever works for cutting the seam. It looked like the bottom was secured to the sides with a hard plastic weld or glue. Carefully cut the glue line. A dremel might work well. So might have an Exacto razor saw. I have both, but they were back at the house (a 20 minute drive) and a hacksaw would have been too wide. So I carefully chipped away with sharp chiselike scraper. It worked, although caused some chips I would have prefered not to have.


3. The bottom slides out by gently prying around the edge.


4. Inside is a can full of charcoal! Dump out into a convenient clean coffee can.


5. Remove the two foam discs at the top.


6. Pull out the plastic screen in center. There's another filter on the other side.

[nograin]

Inside the Can

Inside the canister the two little purge restrictions can be seen. One is inside the center airspace and the other just outside the center within the top airspace. Clean out all the loose charcoal, dust, etc. by wiping and using some air if you have. Clean it more 'cause every little bit will try to find its way to the carb. Don't ask me how I know this.


Replacement Materials
Foam
The foam may have all been 1/4" thick when new. I made two guesses at replacement foam filter material. Both were made of polyurethane. The first was "slow recovery" foam and the other was filter foam. When I got them, I discovered even the open slow recovery doesn't really let any air through. Since the sample pack of filter foam was all 1/8" material, that's what I used, with the fine grade (100 pores per inch) at the top and a medium grade (65 ppi) at the bottom. Next time I'll probably buy 80 or maybe 100ppi but in 1/4" thickness. I bought from McMaster-Carr. I'm sure there are other sources, but they're convenient and fast.

Filter Foam Sample Pack

Rubber
For the purge valve's diaphram, I settled on ECH rubber in 1/32" thickness (item # 85765K1 from McMaster-Carr). ECH seemed to have the best chance at surviving E10 fuel. 1/32" is absolutely the thickest that will work. If you can find something even thinner, it will be easier to reassemble.

[Tripwire]

VERY nice write up- ask a mod to put it in the archives, thanks for taking the time

trip...

[nograin]

Part 2 Reassemble
1. Mark out and cut the foam filter material. Marker and scissors worked well. The donut may need a little trimming to fit snug but flat. On the inside of the center, I kept the original foam as it was 1/4" thick and in semi-good shape. But as insurance placed a piece of 65ppi foam in first. Then the plastic screen, then new replacement foam piece on top (well, bottom actually, but its upside down at this stage).


2. Refill canister with charcoal. A fresh supply from the pet supply (or maybe even McMasters) would have been a good idea, but I forget to get some. Surprisingly, when I poured the old stuff back in, it would have overflowed. I suppose one could shake it for a half hour to try to get it to settle. I didn't. Leave a good 3/8 to 1/2" space at the top (err, bottom) for the bottom screen to go in.

3. Secure the bottom to the sides. Glue was an option; but I wanted to keep it serviceable. I used 4 small sheet metal screws (for triple track storm windows). Pre-drill the plastic the diameter of the shank (root diameter) so the plastic doesn't crack.


Then for belt and suspenders and to make it look nicer, I wrapped it with some self bonding electrical tape.

Purge Valve
Flip it right side up and time to fix the purge valve.

There are two passages from inside the purge valve area down into the main canister. One on the side (visible) and one in the center raised section. The external port goes to manifold vacuum at the back of the carb and so is always pulling as long as the engine is running. At idle, that vacuum overcomes the spring and pulls the diaphram down. This blocks the center passage.



The diaphram has an extra thick center section. This sits inside the spring and when the diaphram is down seals the center.


My first attempt was to simply back up the old diaphram with a new seal made of the ECH rubber. Unfortunately, the 1/32" ECH plus the original (1/64" ?) seal was too thick. The cap wouldn't go on. If you have thinner material, this may not be a problem.

So, from the old diaphram cut a circle keeping the button and enough material to seat on the spring retainer.


The cap will go on with sufficient pressure around the rim.

It holds vacuum! Success!

[nograin]

Vapor Separator

But wait! Before reinstalling, clean the charcoal out of the lines. Better yet replace them with some 3/8 ID "fuel injection" hose. (The FI rated hose holds up better to today's gasoline)

Then clean out the vapor separator. There will be charcoal in it from vapor canister. The charcoal sticks so doesn't shake out. How did I find this stuff was in there? More important, how did I get it out?

The separator consists of a hollow can with three ports. The 3/8" port going to the carb vent solenoid valve extends about 2/3 of the way into the can. Using an areosol carb cleaner, stick the extension tube into the opposite 3/8" port Slide the tip along until it drops into the can body. If you spray and nothing comes out the other big port, you did it right. Spray, shake (cover both ports when shaking, duh), pour out from the side you sprayed into. Repeat, repeat and repeat until nothing comes out. There was at least a couple spoonfuls of charcoal (and foam?) bits in mine.

[JeepJeepster]

Awesome writeup!

Can you explain where you got the 1/32" ECH rubber? Is it just a sheet of rubber or what?

That blue piece looks just like a fuel filter. I assume its not? My FSJ doesn't have anything like that between the canister and the carb.

[twmattox]

I went about this in a slightly different way (figured I would add here in case someone needs the info).

The carbon canister should have a sponge filter at the top separating the carbon from the vacuum and vapor flow. This sponge breaks down relatively quickly and carbon can get "sucked" up. I cut mine in half, dumped out the old carbon, put some mesh fiberglass in the top, refilled with charcoal, and used rubber tape to reconnect the two halves.

This is the inside top. You can see where the sponge filter has been eaten away.

">

I removed the sponge filter and this is what it looks like:
">

A look at the to with the filter removed:
">

Inside bottom (again, sponge filter):


The underside (outside) bottom. This is what that fiberglass replacement filter referenced above covers:


I stuffed fiberglass aquarium filter material in the top:
">

Then, used aquarium activated charcoal:
">

">

">

Then sealed back up with rubber sealing tape:


While I am at it, I may as well show the purge diaphragm removal too. This should show why the purge function doesn't always work (or why there is a small vacuum leak noticed there sometimes):



In the top is a small rubber diaphragm (notice the holes that have been rubbed in by the cap):


More of the holes:

[nograin]

I went about this in a slightly different way (figured I would add here in case someone needs the info)

Thanks! I actually linked to your write up and photos in my first post, but its probably more convenient for most to add it in here.

[nograin]

Awesome writeup!

Can you explain where you got the 1/32" ECH rubber? Is it just a sheet of rubber or what?

Thanks!
I added subheads on earlier post on materials to clairfy. I bought 1/32" because that's the thinnest ECH McMaster-Carr carries. I hadn't taken the canister apart yet so was just going from photos like the ones TWMattox had posted. I chose ECH as the most resistant to the E10 pump fuels. Nitriles and Viton rubbers are also OK with gasoline as best I can tell, although maybe not quite as good. Frankly after taking my canister apart, considering the age and milage, whatever they originally used in the purge valve survived pretty well. The foam, eh, not so good, but not terrible. I'll be checking on the new foam to see how it holds up.

Compatibility of Rubbers with Gasoline Fuels:
Came across these research papers on fuel compatibility with rubber. E15 for some reason seems to be a very aggressive mix. Fortunately most stuff here in the US is less than 10% Eth. When you look at these papers, fuel 'C' is gasoline formulation used in testing. I can dig up the specification document numner later if someone is really interested.

NBR, NBR with vinyl, ECH (epichlorohydrin)
http://digital.ipcprintservices.com/art ... ticle.html

NBR, PVC, Neoprene et al.

http://www.hindawi.com/journals/jfu/2014/429608/

Dupont on six types of Viton(their trademarked product)
http://www.dupontelastomers.com/autofoc ... ensAltFuel

That blue piece looks just like a fuel filter. I assume its not? My FSJ doesn't have anything like that between the canister and the carb.

Right. There 's no filtering in it. My guess is the vapor cools as it passes throguh the metal can. Some portion condenses out and sits in the bottom until it evoprates under slightly vacuum and heat. I'm not sure when they started using the separator.

[twmattox]

Additionally, the charcoal canister has two purge levels...a small purge and a large purge (I assume the large purge removes the vapors from the charcoal and is only active when throttle is present and the small purge is there to prevent a buildup of vapors during long periods of idle).

These are accomplished via metered air bleeds. The small purge appears to have been moved from the canister to the vapor separator...not sure when or why. I just know that the small purge bleed in the canister is plugged on all canisters that I have examined that came from the factory with a vapor separator. The large purge is a part of the canister (the center large purge).

The blue fuel filter looking item is the fuel/vapor separator. The small line is a metered air bleed. If you use a fuel filter, it would allow too much air through that small line and could create a too lean condition.

[nograin]

On the 1985, the purges work as I described.
While the engine is running -
- The primary purge pulls on the canister constantly. It creates a low pressure area in the lower half of the purge valve. This pulls air/released vapor through a restricted passage (about 0.030" dia.) from the cylindrical open chamber in the center of the canister below. In turn this draws air-vapor from the charcoal chamber through two foam filters and plastic screen.
- The seconday purge happens when the ported and manifold vacuum are equal. This is all the time except for slow idle. The additional purge vapor is drawn into the lower half of the purge valve through the passage (about .040" diameter) in the middle of the purge valve. This connects to the upper air dome above the charcoal chamber. This is also communicates to the other ports that connect into the upper dome; which are the fuel tank and the vapor separator.

The vapor separator has just a pinhole connection through to the manifold vacuum. Probably .010" or less in diameter. Very restrictive.

I'll try to draw and scan in some diagrams this evening.

Here's my vacuum routing

[Strode]

Super writeup, thanks for taking the time.

I think I have one laying around I can play with.

[men in black]

X2 Super writeup, thanks for taking the time.

[twmattox]

Not to argue; but, here is way I interpret that vacuum diagram:

The purge signal is connected to spark ported vacuum. This means that that canister purge is only open when the vehicle is not at idle.

The vapor separator "small line" which houses that small bleed, is connected to manifold vacuum and is always pulling a small amount of vacuum.

My canister may be different from yours. Mine will only purge when the signal has a vacuum on it...