75 CJ Vapor Canister

I finally thought i would get to solving the gas odor issue i have when i fill my tank over half full and have read dozens of posts about the vapor canisters. After taking out the canister, i found that its totally empty and has no charcoal remaining in it. The PO must have dumped out the carcoal for some reason. He also put on an aftermarket KN air filter. My canister has three connects on it. One goes to the the liquid check valve near the tank and one ties into the base of the carb. My third one labeled "purge" did not have a hose connected to it - is it supposed to? And if so, where? I see the 74 models have a connection to the air cleaner intake but not sure if this is the case for the 75 model .

Also, a previous post said the canisters were easy to rebuild. I cannot find a way to take the unit apart to fill it back up with charcoal. If some knows a trick, please let me know.

 

I've never rebuilt one.

You have three connections on the factory canister. One is vapor from the liquid check valve and the gas tank. A second vents the float bowl of the carburetor. The third goes to the snorkel of the factory air cleaner. These canisters do not connect to engine vacuum. Instead, the incoming air through the snorkel creates a slight vacuum in the canister, and draws the vapor into the air cleaner. There are no valves and such inside the canister, AFAIK.

You can buy new canister of the later style (with 4 connectons), that purges the charcoal using engine vacuum. These canisters have a valve inside of them (the purge valve) which I believe is connected to ported vacuum. Thus the purge only happens above idle, when the engine is running. Thus they have a purge (purges the charcoal), and a purge valve connection (that opens and closes the purge). The other two connections are the tank vapor and the bowl vapor, as before. If you want to keep the K&N filter and a vapor recovery system, you'll have to use one of this type canister.

Standard CP3045 http://info.rockauto.com/SMP/SMPDetail3.html?CP3045.html

 

Tim - Thanks for the reply. I like your suggestion that allows for keeping the KN air intake but i dont follow you on where i would tap into a vacuum. If there is a specific location i would definately do this. My thought was to drill into the underside of the KN air intake housing to connect a hose but i am not sure i would get adequate draw.

 

I'm sure that drilling into the AC housing would not work. You need the flow of air through the snorkel. The connection for the canister at the AC sticks up perpendicular to the flow of air, just like an old fashioned pump sprayer. The snorkel only about 2" in diameter at that point, and all the engine air goes through it.

Here's the diagram from an '89 Wagoneer - just look at the canister plumbing, not the rest of it.



For the newer style canister, there's a purge signal and a purge. Purge connects to manifold vacuum and purge signal connects to ported vacuum. Do you know what these are? Just tee into those wherever it's convenient. You don't need the vapor separator or the bowl vent solenoid (labeled "bowl vent").

 

Great idea. I think i follow it pretty well but may have a question or two once i dive into the project. I just finished changing out the fuel tank, filler hose and all the rubber fuel hose connections and it may be a few weeks before i get to finishing up. Thanks again for the help.

 

This canister is pretty much the exact same size and has three hose connections. Any reason why this one would not work?
http://napaautoparts.com/Catalog/CatalogItemDetail.aspx?R=CRB220083_0188568284

 

Possible. What's the application? If it does not have a purge signal connection, then it needs the factory air cleaner connection to work.

 

Good point. I guess I would have to find an OEM Air Cleaner. Your original suggestion sounds like it will work well. Ill let you know how it goes.

 

I replaced my missing canister with one I found that seems to be the exact one. If I remember correctly, it is for an '83 Grand Prix. I believe I may have posted on this a couple of years ago, but I don't remember. The canisters are available. You just need to know which other car used it.

 

Since i dont have the original air intake i ordered the Standard Canister that Tim suggested and plan to hook it up per the 89 Wagoneer schematic. However, i am wondering if i need the hose connection shown on that schematic connecting the Carb bowl vent line and Can Purge Line.

 

Well I finally got a chance to give this recommendation a try and i think it was a success. Below are a few pics of the installation. Everything seems to be working. I can tell that the signal flap on the canister kicks in after the engine warms up and the EGR port vacuum kicks in. I can also feel the vacuum at the "breather" on the canister when the manifold purge vacuum kicks in. Comments on the installation would be good - mainly want to confirm i did this correctly.

I dont believe there was good vacuum to the EGR prior to the project. Now i can tell that the EGR is indeed working and it is making for a slightly rough idle and definate sluggish acceleration. My hope is that some adjustments to the carb are all i need on this??? I just rebuilt the carb this past fall and it was really working well prior to installing the canister and replacing all of the vacuum lines.

Also, on the last image, what are the two capped off vacuum ports for at the front base of the carb? My TSM doesnt show these.

 

They go to something specific in your application, but it really doesn't matter. You pnly have two "types" of vacuum to deal with - manifold vacuum, and "ported" vacuum. Manifold vacuum simply connects to the manifold, and is high at idle. Ported vacuum is blocked by the throttle plate at idle, so it goes to zero abruptly as the throttle plate closes. Since these ports are at the base of the carburetor, I'd presume they are ported vacuum. Easy to test.

Your EGR should be connected to ported vacuum, via the EGR CTO. You'll have no EGR when the engine is cold, and no EGR at idle and at low vacuum (WOT). If your EGR is currently connected to ported vacuum, and you have a poor idle, I would remove the EGR valve (get a new gasket first) and wire-brush the pintle. EGR valves often stick open due to carbon buildup.

 

The 1975 TSM helps a lot with emissions-related questions.

One of the ports on the carburetor is for EGR.

 

Thank you Tim. I will definately try cleaning the EGR. It is currently hooked up to ported vacuum. I have three ported vac connections on my carb and currently only one is used and its connected to the EGR via the EGR CTO. After i start the Jeep and its still cold, i can rev the engine and the EGR does not move (I can see the pintle shaft). After two to three minutes, i can rev the engine and see the pintle shaft move in and out commensorate with the RPMs. Its does not seem to "stick" and that is what made me think i need to adjust the carb (i am a novice at best at adjusting carbs). Ill try cleaning the EGR first. If i can get the idle fixed ill be really happy with the application.

 

....actually its not so much a rough idle as it is rough and sluggish acceleration.