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Thread: 75 CJ Vapor Canister

  1. #1
    Join Date
    Feb 2010
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    Ft Worth, Texas
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    55

    Default 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.
    75 CJ5 Apple Green 258/T14

  2. #2
    Join Date
    Aug 2003
    Location
    Medford Mass USA
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    Default Re: 75 CJ Vapor Canister

    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/SMPDeta...ml?CP3045.html
    Last edited by timgr; 11-06-2011 at 01:51 PM.
    Tim Reese
    '75 CJ-6, Copper Polly 304/T15
    '77 J10 type 45 (131" WB) 258/T15/3.54
    '82 J20 type 27 360/T18/NP208/3.73 7600 GVWR
    '95 VW Golf Sport 2D 2L

  3. #3
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    Feb 2010
    Location
    Ft Worth, Texas
    Posts
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    Default Re: 75 CJ Vapor Canister

    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.
    75 CJ5 Apple Green 258/T14

  4. #4
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    Medford Mass USA
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    Default Re: 75 CJ Vapor Canister

    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").
    Tim Reese
    '75 CJ-6, Copper Polly 304/T15
    '77 J10 type 45 (131" WB) 258/T15/3.54
    '82 J20 type 27 360/T18/NP208/3.73 7600 GVWR
    '95 VW Golf Sport 2D 2L

  5. #5
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    Feb 2010
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    Ft Worth, Texas
    Posts
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    Default Re: 75 CJ Vapor Canister

    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.
    75 CJ5 Apple Green 258/T14

  6. #6
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    Ft Worth, Texas
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    Default Re: 75 CJ Vapor Canister

    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/Cat...083_0188568284

    [IMG]Desktop\canister.jpg[/IMG]
    75 CJ5 Apple Green 258/T14

  7. #7
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    Default Re: 75 CJ Vapor Canister

    Quote Originally Posted by Gigem1983 View Post
    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/Cat...083_0188568284

    [IMG]Desktop\canister.jpg[/IMG]
    Possible. What's the application? If it does not have a purge signal connection, then it needs the factory air cleaner connection to work.
    Tim Reese
    '75 CJ-6, Copper Polly 304/T15
    '77 J10 type 45 (131" WB) 258/T15/3.54
    '82 J20 type 27 360/T18/NP208/3.73 7600 GVWR
    '95 VW Golf Sport 2D 2L

  8. #8
    Join Date
    Feb 2010
    Location
    Ft Worth, Texas
    Posts
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    Default Re: 75 CJ Vapor Canister

    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.
    75 CJ5 Apple Green 258/T14

  9. #9

    Default Re: 75 CJ Vapor Canister

    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.

  10. #10
    Join Date
    Feb 2010
    Location
    Ft Worth, Texas
    Posts
    55

    Default Re: 75 CJ Vapor Canister

    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.
    75 CJ5 Apple Green 258/T14

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