My Tech How-To for the Carbon Vapor Canister

[scotty1998]

So, I got tired of rough idle, questionable acceleration and surging and have investigated the purge valve inside the vapor canister. It looks like swiss cheese so, there's my vacuum leak. You can't find replacement valves for these things so you're stuck with doing one of several things. Putting "shoe goo" on the holes in the valve (tried that and now it's worse), figuring how to duplicate one out of similar material (don't want the hassle), finding a junk yard dog (without a holey purge... yah good luck), disconnecting the entire can (too much gas odor in the cab) or, trying to locate a close copy for little $$.

Sooo. I went over to Rockauto.com and found a match for a 1991 Grand Wagoneer. It's a Standard Motor Products # CP 3045. I believe it's got either 3 or 4 ports, two for vacuum and perhaps one for inlet emissions. The original has 4 ports however, I have no reason to believe that this will not work if it turns out to be truly 3. I figure I should be able to tee in my gas tank and carb vent together to plug into the passive inlet. The two vac ports should match my feeds from ported vac and from the PCV.

Best of all is that this thing only costs $30. It should arrive late this week. When I get it in, I'll post pics and any modifications that I might have to make to make it work. I know this subject has been hotly contested, especially on where to get a replacement...

Originally Posted by scotty1998

Could you please update the following link since I don't have access rights to do it myself?

Apparently, Standard Motor products discontinued the part number that the article refers to, CP3045.

I found a similar NAPA Echlin number that can be used instead CRB 220052

Thanks for your help.


http://www.ifsja.org/forums/vb/showthread.php?t=106051

[BlacksheepGW]

Pics and a write up! I am about to order one myself to fix some issues. Thank you for this post, it solves a few issues I am looking at!

[scotty1998]

If you've experienced poor or rough idle, quirky acceleration, strange responsiveness to throttle, surging, and a never ending balance of power between too rich or too lean, then this write-up could be for you.

One of the things that's always bothered me about emissions on our Jeeps is an inability to find a match for the OEM Carbon Vapor Canister. What is a vapor canister you say? Well, it's that strange looking little black cylinder that sits on the passenger side fender wall with four hoses sticking out of it.



It's function is actually an important one. It captures fugitive fuel vapors that come from our gas tanks and carburetor during expansion. Fuel is volatile after all and unless something is there to control these vapors, the result is an endless trail of gasoline odor under the hood, in the cab, in your clothes, in your garage, three cars down at the shopping center... you get the idea. Anyhow, the canister is filled with carbon which helps to reduce odor by adsorption... topic for another day I suppose but the primary principle is, vapors in, no vapors out. These vapors are contained until you fire your rig up and that's where the vacuum system comes in. A spring loaded diaphragm lies under the cap of the vapor canister. Vacuum draws the diaphragm up and vapors are pulled out of the canister and through the the PCV system and into your intake. Voila, a mini-air treatment system.

The problem lies with that diaphragm. If you open up the cap on your OEM can, you'll find a spring, a ring shaped guide and a swiss cheesy looking rubber circle. Should it have holes in it? No and guess what? That seems to be a good source for a vacuum leak don't you think? Think that could cause rough idle, weird acceleration, engine to run lean, and a host of other problems? You bet.

Now, for those of you who have already delved into this and have gone down to the local parts store expecting a quick replacement, you'll receive either blank stares, or a large catalog with lots of these little monsters to choose from. Problem is, they're mostly for modern cars and can range anywhere from $20 to $200. Where to start? No idea? Read on...

I happened to be on RockAuto.com the other day and typed in every production year of the late model Grand Wagoneer that I could think of. Nothing for 87 - 90 but I seemed to hit gold for a 91. But wait... the listing was for a 91 - 93 Grand Waggy? An obvious error... do I take a chance? Yes and I placed my order.

For $30, here's what I got. A Standard Motor Products #CP3045 Vapor Canister. Pulling it out of the box I noticed that it wasn't an exact match. Do I send it back? No. Retrofit time. In the photo below, you'll see our OEM can on the right and the new one on the left.





Here's a side by side view





A view from the bottom. Note that the old vent with air filter is no longer routed this way on the new one. The bottom on the new can is completely sealed.




Here is a view showing a comparison of the diaphragm components. They are a different design but their function is basically the same. Note that there is an extra part on the new side. A breather cap.


------------------------------------------------------------------------

Now for the retrofit.

Looking at the new can from the front we see several things. There are two ports on the extreme left side and the extreme right side. When you pull the can out of it's new box, these ports will have plugs molded into them from the factory. These will need to be removed. I took a drill bit and just drilled them out. Took me maybe 3 minutes. Careful not to overdrill or you'll poke through the Nipples. After this is completed, suddenly, you'll realize that this new can is starting to resemble the ports of the old can. There's only one exception now however. You'll note the largest port beneath the PCV connection isn't a hose port at all. It's a breather which replaces the old breathing system on the bottom of the old one. There's an X shaped cap that fits in here to keep dirt out. Insert this cap and now you have everything you need to make a bolt in swap.




Here are photos of the finished product. It really wasn't a very difficult project at all as most of the time was spent trying to figure out what each port was for since there are no instructions that come with these things. In addition, I had to put some new hose on a few of the leads since they were a little too short to stretch to the new can. The nipples are set back a few inches behind the can as opposed to the old one where they lean out over the can's front.

The end result? My idle has completely smoothed out, no more surging, and my acceleration is smooth as butter. Please PM me if you have anything to change or add. Thanks and good luck!

[Chuck Brown]

Awesome write-up Scotty, definitely tech-archive worthy!

Im wondering though, my 77 Cherokee had no vapor cannister when I bought it off the PO, what year did these become stock? The first time I recall ever seeing them was in an '87 Chebby pickup I owned.

When the PO installed the 401 in my 77 Chief, he just plugged the outlet on the POS Holley carb he installed, and I can smell the fuel. Since I had already pulled the can and hoses off an '88 GW I found at the junk yard a couple months back, should I refit my current setup for the vapor can?

Thanks,

Chuck Brown

[scotty1998]

Chuck,

I really don't know when these cans first became stock but I do know that they were on the early 80's vehicles. The problem with rigging up the setup with a junk yard PO one is the diaphragm. As I understand, it is very rare to find one without holes in it so I'd hate to recommend you going through the hassle only to find that now you have vacuum problems. That's why I was so bent on finding a whole new replacement.

The other problem that I'd have with recommending it is that I don't know what the late 70's PCV system looks like. In the late model, the actual PCV valve is tee'd off to the canister.

However, as long as all of the above checks out ok, it certainly can't hurt. The PCV valve tee's to the nipple just below the cap, a ported vacuum source off the back of the intake is connected to the cap nipple, a gas tank vent hose connects to the one remaining nipple and the final one goes to the Holley outlet that you mentioned

Let me know how it turns out...

[tgreese]

Originally Posted by Chuck Brown

Im wondering though, my 77 Cherokee had no vapor cannister when I bought it off the PO, what year did these become stock? ...

Some '77s have a canister. They were used at least as early as '72 or maybe '71 in California. The '77 FSM will tell you which devices were used on your vehicle. Fuel tank vapor control was used on all CJs and on CA FSJs in 1977.

Scotty1998, glad this worked out so well.

[Fiodh. Argus]

Hi Scotty
great write up, very informational! Thanks for the trouble you took.

Chuck, my 77 has a cannister and it shows one in the manual. Perhaps it was a California thing and some states might not have had it?

learned a lot today.

[BlacksheepGW]

My wife and I just got back from the 'yards. She found one from a 1993 Jeep Cherokee XJ (Baby Cherokee). I look at Rock Auto, and its the same part number

I am not sure the difference, but I can only assume (I know, I know, I shouldn't.. but..) it filters a little better.

I also found out that most of these canisters are an AC Delco emission part. I Pulled one very similar off a late 80s GM truck, and one that is almost perfect off a 1980 Chevy Nova.

AWESOME WRITE UP!!! THANK YOU!!!!

[Danbert]

Great write up!
One question though. What are the studs on top of the last picture? Mounting? or to ground the canister for static discharge?

[scotty1998]

I'm not entirely sure what the studs are. At first I though that they were part of the canister assembly process so that you could take the top off of the bottom if you ever wanted to replace the carbon inside. For $30 though, seems like it wouldn't ever be worth the effort.

[jdaniel83]

Could they possibly be used for mounting or installation purposes? Maybe on the models the canister is intended for there's a bracket or something that goes on top.

[79 CHKCHK]

hmmm...i just took a look at mine on my 79 cherk. nothing in there. completely hollowed out the pcv line and vac line are missing. both are capped off. shes been running fine for the past 6months or so that ive owned it except for a couple of clogged fuel filters. but i carry two spares for that. someday ill get around to replacing the fuel lines and cleaning the tank.

[skinnyD]

My jeep is having evey single one of those symptoms and now Im thinking its been the vapor canistor all along. There is what looks like a fuel filter coming out of the carb line and into the canister. The arrows on it indicate air flow towards the canister. Can this be eliminated? I was replacing rubber hoses there today and there was definately a small amount of gas in the hose. I think from before the carb rebuild. Sorry for the hijack!

[BlacksheepGW]

Originally Posted by skinnyD

My jeep is having evey single one of those symptoms and now Im thinking its been the vapor canistor all along. There is what looks like a fuel filter coming out of the carb line and into the canister. The arrows on it indicate air flow towards the canister. Can this be eliminated? I was replacing rubber hoses there today and there was definately a small amount of gas in the hose. I think from before the carb rebuild. Sorry for the hijack!

That'd be a vapor separator and I am not sure it can be eliminated. I am not completely sure how it works, I just now it woks and is there...

here:
http://oljeep.com/gw/vac/85/85_FSJ-V...ection-360.jpg

[gte901m]

Nice write up - I need to do this.

[scotty1998]

I think the thought that those studs are for another model's bracket is more plausible than anything. Definitely not for us though

And, I agree. Leave the condensation/liquid/vapor seprator where it is. It keeps moisture out of the can. (At least that's what I've been told)

[Jayrodoh]

Awesome write up! Mine is shot and I've bought two from members only to have the same problems and a box of charcoal.

[Fiodh. Argus]

Originally Posted by Jayrodoh

Awesome write up! Mine is shot and I've bought two from members only to have the same problems and a box of charcoal.

I guess you could have a BBQ

[j20brett]

So i cant exactly tell from the pics, but the breather is 100% capped off correct?

[BlacksheepGW]

Originally Posted by j20brett

So i cant exactly tell from the pics, but the breather is 100% capped off correct?

No, it has little open passages on the nipple that goes into the breather hole. I may use a peice of hose and run it up the side and out for better ventilation, or use a filter on it.