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Vacuum Routing For The 232 Engine

Discussion in 'Intermediate CJ-5/6/7/8' started by Jeff Bromberger, Mar 23, 2020.

  1. Mar 23, 2020
    Jeff Bromberger

    Jeff Bromberger Quarantined in the Garage 2020 Sponsor 2019 Sponsor

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    I felt like this one deserves a separate thread because of the universality of it.

    I'm trying to re-plumb the vacuum lines for my Jeep. It has a 1975 vintage 232 engine. That means it has an EGR, a CTO with 3 legs, a charcoal can, a PVC valve, a Carter carb with two different vacuum ports (one at the very bottom, right at the gasket, the other further up but still on the lower third of the unit). It also has a LARGE port on side of the intake manifold, a SMALL port on the top of the intake manifold (and it's crimped shut), oh, and the vacuum advance on the distributor. That's 11 ports in total!

    Generally, it all makes sense if you can figure which vacuum is where. The TSM talks about straight manifold vacuum and "ported" vacuum. And to make matters even more interesting is the operation of the CTO. The center port is connected to the "1" port when the coolant is cold, and it shifts to connecting to the "2" port when the coolant is hot.

    I know that the LARGE port on the intake manifold uses a large hose to connect to the PVC. I have never seen a T on that line in my experience. Put together with a tube from the air cleaner to the rocker cover, that's the crankcase air flow.

    My TSM doesn't explain the use of the two vacuum ports on the carburetor. It also doesn't talk much about the CTO - I know the distributor goes on the D port (the center) but which vacuum is used when the engine is hot, and which when it's cold? And, to top it off, there's that crimped-shut port on the top of the manifold that might have gone somewhere.

    So, wizards of the less than atmospheric pressure, what goes where?
     
  2. Mar 23, 2020
    Lockman

    Lockman My " Rosie" 2020 Sponsor 2019 Sponsor

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    CTO = Coolant temp Override switch. Any way, Hope this helps :
    CTO 232 Vacuum Diagram.jpg
     
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  3. Mar 23, 2020
    timgr

    timgr Jeepin' Nerd 2020 Sponsor 2019 Sponsor

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    Some of this is copied JonBrew's thread about the 2G ports on the early forum.

    Vacuum is used as both a signal (operational information) and as a source of power.

    One port at the bottom of the carburetor should be "ported vacuum." It is different from "manifold vacuum" only at idle. There is a passage from the port to the venturi, and that port is physically blocked by the throttle plate when the throttle is closed. Ported vacuum goes to zero at idle. At any other speed, it's the same as manifold vacuum.

    Any passage into the manifold is manifold vacuum. Ported vacuum only comes from the base of the carburetor.

    Any passage at the top of the carburetor (in the air horn) is a source for clean air, not vacuum.

    You can identify the ported vacuum source using your vacuum gauge, or I suppose you could take the hose off while at idle and see if there's any vacuum there. You can probably look at the base of the carb, see the passages that are blocked by the throttle flap. If I had the carburetor off, I would test the ports with my MityVac (haven't done this but it should work). The ported vacuum ports should be obviously blocked when you try to pull a vacuum on them and the throttle plate is closed.

    Ported vacuum is often used for distributor advance, so that idle has less advance than otherwise. You can alternatively use manifold vacuum for vacuum advance, with worse emissions. The CTO will change from manifold to ported vacuum as the engine warms up. Less advance at idle gives lower emissions, but the the engine will run better at idle when cold with more advance.

    You need two CTOs - one with three nipples (select ported or manifold vacuum) for spark, and another with two (on-off) for EGR.

    Ported vacuum is also used to control the EGR valve. The EGR valve adds exhaust gas (essentially plain air depleted of O2) to the air-fuel charge. This dilutes the air-fuel charge, lowering the combustion chanber temperature and reducing the conversion of nitrogen to oxides NOx. Essentially it allows the burn to be both lean and cool, giving low hydrocarbons and low NOx in the exhaust. When the engine is cold, EGR will be shut off and presumably the mixture will be richened by the choke. The engine can't take much exhaust gas dilution at idle, so ported vacuum turns the EGR valve off at idle, and full-on when you are cruising down the highway (both high vacuum conditions).
     
    Last edited: Mar 24, 2020
  4. Mar 24, 2020
    timgr

    timgr Jeepin' Nerd 2020 Sponsor 2019 Sponsor

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    Jeff, it seems like you want to put back all the emissions devices that were there from the factory. Which year's scheme are you aiming at? 1974 for the Jeep or 1975 for the engine? Meeting the 1974 standard could be slightly easier than 1975, but maybe not. Internally I expect the two years to be identical. I suggest that you follow the scheme for the 1974 CJ-5, delivered NW (nationwide, 49 states, ie not California). The 1974 TSM is free to read and download at the Tom Collins site. https://oljeep.com/gw/74_tsm/4A-EmissionControl.pdf

    I would start at the back of the emissions chapter with the table of applicable devices.

    1974emissions.png

    You only have 7 systems to deal with. The engine was built with the proper cam and carburetor to be compliant. Nothing to do there, assuming you are using the proper replacement cam and the original carburetor. You'll need to tune the carb to factory specs, including choke, fast idle, idle mixture and idle speed.

    For EGR, I went over it some above. You need the EGR valve and gasket, the proper CTO, and the tubing. Figure 4A-8.

    For the TAC, you need the factory air cleaner. There is no vacuum connection. You need the paper/foil air duct, and the sheet metal stove on the exhaust manifold IIRC.

    TCS is a solenoid valve in the vacuum line between the distributor and the vacuum source. There is a switch on the transmission that closes the valve above 34 mph. The vacuum source is the distributor signal from the spark CTO. See figure 4A-32. You will need a switch that's compatible with the A727. All the civilian Jeeps in this era with an automatic were the TH400, which won't work with your transmission. I took a quick look at the '80-up Wagoneers and it seems that the TCS was gone by the time Jeep adopted the A727 in place of the TH400. You will have to figure something out (maybe your transmission already has this switch), or just omit the TCS system.

    Spark CTO is also shown in figure 4A-32. You will need to figure out which nipples to connect to.

    PCV is pretty straightforward. You need a source of filtered air to the crankcase (from the air cleaner) and the PCV valve going usually to the big manifold vacuum port at the base of the carburetor.

    FTVEC is super simple for 1974. All you need is the canister, hoses and the factory air cleaner. No vacuum connection.

    The emissions devices are a lot like electrical - just go one circuit at a time and connect to the proper type of vacuum - ported or manifold. Block off the connections you don't need, tee up an additional port if you need more.
     
    Last edited: Mar 24, 2020
  5. Mar 24, 2020
    Jeff Bromberger

    Jeff Bromberger Quarantined in the Garage 2020 Sponsor 2019 Sponsor

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    This'll be a first half - second will follow with pictures.

    I'm going to put it back more or less to 1975 standards. The 1974 didn't have an EGR from what I can tell, so the manifold is different. So I'll go with what I have been given (in the cosmic sense).

    This engine only had a single CTO installed - I would not even know where to install a second one. My old (1974) block had no CTO, and you can see the port plug/cap in my old photos where the old boy was cracked and was leaking.

    I need to look again at the carb and get more info. As Ahnold once said, I'll be back!
     
  6. Mar 24, 2020
    Lockman

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    " I'm going to put it back more or less to 1975 standards "
    That's why I sent you the ' 75 vacuum diagram for a 232 that you inquired about ?
     
  7. Mar 25, 2020
    MA74CJ5

    MA74CJ5 Member

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    A 1974 would definitely have an EGR system and the 2 CTO switches that Tim mentions. The 1975 systems are virtually identical and would have also included the EGR and dual CTO switches. I know 75 is also the first year of the cat converter. I don't think the air pump had appeared yet but it may have. You may have an aftermarket manifold if the EGR port is missing.

    BTW the EGR mounts on the side of the intake manifold and the 2 CTO switches screw into the drivers side of the block roughly halfway down, in line with each other about a foot apart. I can take a pic of this if it's helpful.
     
  8. Mar 26, 2020
    timgr

    timgr Jeepin' Nerd 2020 Sponsor 2019 Sponsor

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    My first CJ-6 bought new in 1975 had a 258 with the Air Guard (air pump) device. This conflicts with the 1975 TSM, but my Jeep was from the very tip of the tail of production for 1975, supposedly one of the two final domestic CJ-6s that Jeep built.

    Jeff, you can configure the devices however you like. Unlikely that anyone will ever question the emissions setup on a 1974 agency vehicle, so build it the way that makes you happy. It's also possible that the agency vehicles were delivered without EGR in 1974; seems more likely that the engine or manifold was swapped around sometime in the Jeep's history. Seems very unlikely that the USPS would spec a lower emissions standard for their fleet than what was being delivered to the public. And I expect the cost of the agency engines would then be higher because they would have to build the engines differently from what was going to the civilian assembly line.

    [​IMG]

    I see two places for CTOs here.

    I'd also claim that, if you have the original carburetor and it was made to work with EGR, the engine will run better and undoubtedly cleaner equipped with an EGR valve. Post up the tag number from the carb you will use.
     
    Last edited: Mar 26, 2020
  9. Mar 26, 2020
    Lockman

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    My 2 cents here about the Catalytic on 1975 models. It was only required on the V8's , even in CA. My ' 75 TSM refer's to this.
     
  10. Mar 27, 2020
    Jeff Bromberger

    Jeff Bromberger Quarantined in the Garage 2020 Sponsor 2019 Sponsor

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    OK, so here's what I have. The 1975 motor has the EGR, and that's good enough for me. The one piece I am scrapping is the California Only Back Pressure sensor. The standard 232 didn't have this, and I'm not in California.

    As for the vacuum sources - ported vs. manifold. Here's a pair of photos from my Carter YF:
    Carb_Base_1.jpg Carb_Base_2.jpg

    Both of these vacuum ports (and these are the only two I have) are on the throttle body portion of the carb. There's one more or less over the idle set screw (seen on the left) and one possibly narrower one right at the base of the unit. Is there one of these I should use? Both? Cap one or the other?

    As for the site of the second CTO:
    Block-Left-Primed.jpg

    If you follow the mid line back, below the freeze plugs, the first two are screw holes for mounting something. The next round port, just above the others, is where the original 2-port CTO was found (and I'm putting in a 3-port one, as per TSM). I have to check what's going on between cylinders 4 and 5 - see if that is a plugged access port or something else. That would be the only place for a second CTO on this block.

    Thanks for helping me with this. I just wanna get this thing running at least as good as I can, which probably means factory spec, within reason! I'm not going to go so crazy as to install a cat converter, so that's where I'm drawing the line.
     
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  11. Mar 27, 2020
    timgr

    timgr Jeepin' Nerd 2020 Sponsor 2019 Sponsor

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    I can't say by looking. I would guess that the port lowest on the base casting of the carb. Somebody more familiar with the YF may be able to say. I would try looking inside the throttle bore for where the passage originates. The throttle plate will block that passage at idle. Or just test it on the running engine. All you need to start it up is manifold vacuum to the distributor and plug everything else. Yes regarding the second CTO threaded hole. NP! :coffee:
     
  12. Mar 27, 2020
    timgr

    timgr Jeepin' Nerd 2020 Sponsor 2019 Sponsor

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    Also, here's the '75 table:

    CJ75emissions (557 x 600).jpg

    Strangely, Jeep specs no EGR for the '75 NW 232 CJ. However, it does have TCS, which I suspect will be harder to duplicate than the EGR system.
     
  13. Mar 27, 2020
    sterlclan

    sterlclan Member

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    Fwiw the wife’s 76 has no converter never did has a tag on the dash stating non catalyst. No Tcs either just an egr.
     
  14. Mar 27, 2020
    MA74CJ5

    MA74CJ5 Member

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    Typically you would need one ported vacuum port for the vac advance system which is usually the lowest on the carb (but test that it is in fact ported), 1 port designated as EGR (I think it's the top one but double check) and manifold vacuum which comes from a port on the manifold. Since it has been pointed out that non CA in 75 has no EGR I guess you can cap it. Sorry for the misinformation on the EGR earlier - I can't believe Jeep didn't use it nation wide in 75 because I know went back to it in later years.

    Again, my experiences are based on the 1974 year. The first CTO port is for EGR. 1 line from the carb and 1 line to the EGR. The second CTO port was for Transmission Controlled Spark (TCS) which is really not necessary. The other function of this port is to apply full manifold vac to the vacuum advance when the engine is cold and ported when warm. This function is useful. I would run one line from the dist vacuum advance to one of the ports (center in 74), full manifold to one of the others (outer in 74) and ported from the carb to the 3rd port (inner in 74). Obviously double check these ports for 75 if you use this system.

    Hope this makes sense.
     
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  15. Mar 27, 2020
    timgr

    timgr Jeepin' Nerd 2020 Sponsor 2019 Sponsor

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    I would not worry too much about consistency with the printed table (not directed sp. at you but just anyone who's interested). Clearly the mix of components was changing in this era - presume Jeep was searching for the best trade-off in emissions, cost and drivability, while keeping up with the evolving standards - and the TSMs were printed way early, before the beginning of the model year. Jeep also had a lot of mid-year changes, which may be the way with other manufacturers too. Visibility of the actual devices was so low that only the line mechanics would care at the time, and they were covered by the usual Service Bulletin channel.
     

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