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Thread: E21 318i vac pipes

  1. #1
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    E21 318i vac pipes

    I have a vac pipe disconnected on my european spec (no anti smog devices) 318i.
    The car has mechanical inyection same as the late US bound 320i.

    There is one vac pipe coming from a T from the crankcase to the distributor and then there is one coming from the inyection but it is not connected and there arent any more available plug ins (at least I dont see them) on the distributor.

    It starts very well from cold and it takes some gas to do it when hot, otherwise the car runs very smoth and iddles without surging at an indicated 900 rpm. Gas mileage is ok too.

    Does someone know where should i connect said vac pipe?

  2. #2
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    Hi ...

    A picture of your setup would help, but unfortunately you have to make 15 posts here before you can post pictures.

    So my best guess is that you have a distributor with both vacuum advance and retard since you have an extra vacuum line as well as the one coming from the manifold.

    The pic shows where the vacuum lines attach if you have that setup. The one on the left is sticking downwards at about 45 degrees and hard to see.

    This is a right hand drive Australian specifications 1981 model.

    hope this helps ....
    Cheers
    Attached Images Attached Images
    hmm .. Wonder what happens if I do this ...

  3. #3
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    Thanks a lot GDAus, i’ll look if I can see the left attach as per your pic.

  4. #4
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    I looked more closely today on my engine bay and i have 3 vac pipes that i can see:

    1- one connects the breather to the distributor
    2- another pipe connects the hose inmediately after the thermostat and goes to distributor as well
    3- then there is a pipe coming from the manifold which is not conected. It has a lenght that co7ld reach the distributor quite easily but there arent any other plug ins available.
    What is the purpose of this vac pipe? what could i do with it?

    i’ll try to post pics now that i’m 15 post old

  5. #5
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    I enclose some pics of the vac pipes

  6. #6
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    Hi again ... judging from you pics there are a few things going on.

    One common thing with the 1.8 litre engine is that the vacuum advance and retard hoses are often been fitted around the wrong way on the distributor. The earlier 2.0 litre engines with point ignition had a distributor that rotated clockwise while the 1.8 litre engine with the electronic ignition had a distributor that rotated anti-clockwise. The common Haynes workshop manual was written based on the earlier 2 litre model and shows a diagram with the lines correct for the 2 litre and I think a lot of people over the years have referenced it without realising it was not correct for the 1.8 litre.

    My e21 318i had the vac lines around the wrong way when I first got and I got fooled for a while by the Haynes manual.

    I'll try and take some pics of my own setup tomorrow to make things clearer.

    But for the moment I'll try a description.

    The advance hose should be connected from a vacuum port on the engine side of the throttle body next to the idle adjust screw ... that should then go to a thermostatic valve on a fitting in the radiator hose from the top of the cylinder head down to the thermostat. The thermo valve should have one port straight out and one at an angle. One should be labeled "To Carb" ... I think it is the angled one, I will have to check tomorrow. Which ever is marked "To Carb", is the one to connect to the throttle body. The other one goes to the vac port at an angle under the back of the distributor. The thermo valve in the cooling system is to prevent any vac advance until the engine is "warmed up".

    The vacuum retard line should be connected to "manifold vacuum" via a port on the intake manifold on the engine side of the throttle body. See pic.

    The T connector in the hose from the camshaft cover usually connects to the intake manifold as well. This is to act as as balancing passage to prevent the engine from stumbling or stalling if the throttle is shut suddenly.

    For the fuel injection to work properly, all the vacuum lines need to be in top condition. Any air getting into the engine via leaks will stop the air flow meter from accurately injecting the right amount of fuel to give best performance.

    Hope this makes sense
    Cheers

    Graham D
    Attached Images Attached Images
    hmm .. Wonder what happens if I do this ...

  7. #7
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    Thanks again GDAus. I have ordered the Haynes but i gather isnt gonna be a good help for understanding vacuum layout in my european 318i.

    The vac line you ask (black one with a white line on it) is the one that isnt connected and is quite long to reach anywhere really.
    i take note to replace the other one. BTW what is the WUR?

  8. #8
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    Quote Originally Posted by Classico View Post
    Thanks again GDAus. I have ordered the Haynes but i gather isnt gonna be a good help for understanding vacuum layout in my european 318i.

    The vac line you ask (black one with a white line on it) is the one that isnt connected and is quite long to reach anywhere really.
    i take note to replace the other one. BTW what is the WUR?
    Hi again ... I have to work away from home sometimes and that makes it hard reply quickly at times.

    But, I have some time now.

    So the model I have out here in Australia isn't exactly the same as the Euro models ...it's basically a Right Hand Drive Swedish model because their anti-pollution requirements were a match to ours. Information for mine was basically non-existant out here, so I have spent some years figuring out how it works. Mine had been messed around with a lot and was running like a tractor when I got it, but after putting things back to something like they should be it has good acceleration in 4th gear when you floor the accelerator (for the engine size and the time it was designed).

    First off ... apologies .. WUR is short for Warm Up Regulator .. this a a Control Pressure Regulator that varies the control pressure which regulates the fuel mixture being injected into the engine.
    Basically ... cold engine - low control pressure to give richer mixture as the engine is warming up.
    hot engine - higher control pressure to give leaner mixture for normal running.

    Our WUR's also have a vacuum connection from the engine side of the throttle valve in the intake manifold and that allows the WUR to react to the engine load and throttle position and adjust the fuel mixture as needed. Also if the throttle is opened quickly to accelerate .. it reduces the control pressure to give a burst of extra fuel equivalent to the "äccelerator pump" in a carburetor.

    K-Jetronic Fuel Injection is a mechanical based system and the air flow meter (AFM) is operating a mechanical linkage and this has some unavoidable inertia issues. So if the throttle is closed suddenly the AFM can "overshoot" and close too far and cause the engine to falter or stall. So there is usually some sort of balance pipe from one side of the throttle plate to the other.
    On mine ... it runs from from a "T"connector in the vacuum hose connecting Intake manifold to the WUR and connects to the "T"connector in the vent hose from the top of the camshaft cover.(that's the point on yours which is connected to distributor at the moment)

    Finding a small bore "T" connector to go into the vacuum line with the white stripe would be the easiest way to fix that. Finding a suitable T to go in the vac line the the WUR could be difficult.

    The diagram is one I did for myself as I figured out how mine was connected. the advance/retard connects should be the same for yours EXCEPT I doubt yours would have the system that only allows vac. advance in 4th and 5th gear. That seems to be a part of the anti-pollution setup on my model.

    It looks like yours has been messed around quite a bit! Is the vac. line from the underside of your intake manifold is open at the end? .... If it is ... your mixture has probably been adjust to compensate, so putting everything back to how it should be, will need to readjust of the fuel/air mixture to get it to run properly. You will need a long 3 mm allen key for that.

    Hope this makes sense ... I had all this done and was interrupted and the auto save messed up and I had to start again ... grrr ... the joys of forum software

    Cheers
    Attached Images Attached Images
    hmm .. Wonder what happens if I do this ...

  9. #9
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    Hi there- just to clarify, in your diagram, is the retard line going to engine vacuum, and the advance line going to ported vacuum (at the throttle plate?)

    What purpose does eliminating the advance on a cold engine serve? Does it run better when cold with less advance?

    I'm asking because on my car, that temp-sensitive vacuum switch has been removed from the thermostat elbow and the hole brazed up..

    I've played with the options of manifold or ported vacuum for the advance (and the opposite for the retard), and currently am running ported vacuum advance, with the retard disconnected. And it's not quite ideal.

    thanks!
    David

  10. #10
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    Quote Originally Posted by cgifool View Post
    Hi there- just to clarify, in your diagram, is the retard line going to engine vacuum, and the advance line going to ported vacuum (at the throttle plate?)

    What purpose does eliminating the advance on a cold engine serve? Does it run better when cold with less advance?

    I'm asking because on my car, that temp-sensitive vacuum switch has been removed from the thermostat elbow and the hole brazed up..

    I've played with the options of manifold or ported vacuum for the advance (and the opposite for the retard), and currently am running ported vacuum advance, with the retard disconnected. And it's not quite ideal.

    thanks!
    David
    G'Day David...

    I started to give you a reply last night, but it was rapidly turning into a dissertation on engine thermodynamics and a whole lot of other things

    So I thought I'd come at it from a different angle .... so it comes down to Engineering Design Philosophies .... Different countries have tended to evolve their own ways of doing things ... quite often similar but with small differences .. but sometimes very different.

    When I first got my 318i here in Australia .. I was used to British/Japanese/Australian/American ignition systems, all basically similar, so I was surprised with the setup on the M10. It took me a while to sort out all the nuances of the way BMW choose to do it. German engineers coming up with something that is complicated, but gives more precision in controlling the ignition timing for different engine speeds and load conditions .... who would have guessed that happening.

    Since you have a '78 323i ... I'm assuming it has points ignition and you don't have any anti-pollution stuff on it (?).

    Okay .... an engine with fixed ignition timing would only run at a narrow range of RPM because the High Voltage to cause the arc across the spark plug electrodes needs time to be generated, it isn't instantaneous! Also when the fuel/air mixture ignites, it's a controlled burn producing a large amount of waste gases that creates high pressure to push down the piston so the burn needs to start some time before the piston reaches Top Dead Centre (TDC) ... or you simply wont get a reasonable amount of power out of your engine. So everything has to be "timed" just right for different RPM/Load conditions ..too soon .. and you get pressure above the piston before TDC working against it, or too late and the piston is all ready going down and you lose an amount of energy. Both these processes take a reasonably "fixed"amount of time to happen ... so the firing point needs to be some time Before TDC (BTDC) ... and as the RPM's rise .. this point needs to be further advanced. That's what the centrifugal advance is for. But sometimes under different load conditions the engine needs more advance .. so an additional vacuum advance is usually fitted to road cars.


    There's a lot of reasons for "eliminating the advance on a cold engine" , but the main one is that the engine is rotating much slower than even idle speed so that igniting the Fuel/Air mix too soon and it is impeding the rise of the piston. Also chemical reactions are slower at lower temperatures so the combustion process initially is a bit slower .... one of reasons for the thermostatic valve to limit vac. advance until the engine is at it's normal operating temperature. So yes, a cold engine needs less advance!

    Ported versus Manifold vacuum .... the vacuum from these two places is different ..
    Ported vacuum is always used for vac. advance because it is a "venturi" vacuum ... so it taps into the airflow going at higher velocity through the venturi where the throttle plate is .. so it is mostly related to the engine speed .... and when the throttle plate is closed at idle .. this shuts down the port cutting off the vac. advance at idle when the engine is under a "no load" condition running at low speed.
    Manifold vacuum ... taping into the vacuum between the throttle plate and the engine gives an indication of the load on the engine. At part throttle conditions the throttle is restricting the amount of air can can flow into the engine so there is more vacuum .. at Wide Open THrottle (WOT) air can flow freely into the engine and there is less vacuum.
    So in the case here .. part throttle = more vacuum = ignition timing retarded
    WOT = less vacuum = ignition timing less retarded

    So BMW, by using a combination of centrifugal advance/Vacuum Advance and Retard, have a system that can give a more accurate timing map for all the different load/speed/temperature conditions for the engine.
    The thing to understand is that the vac. advance and retard are working together under most situations to give the best engine timing for all the different load/engine speed temperature combinations you get every time you drive your car. SO the actual advance .. is a combination of the advance and retard.

    Then we come to complying with emission regulations and fuel economy standards. The drawing I posted is the System Australian vehicles need to comply with our emission regs. So all it needed was a simple passive air injection system, and a different timing map! Not allowing the vac advance to work in the lower gears was so the revised timing map could cope with a leaner fuel mix to meet the Aussie co2 & HC levels for City driving. Allowing vac advance in 4 & 5th allowed better economy in open road conditions.

    Even the M20's out here could get away with the same basic modes

    By comparison ... the local versions of GM, Ford and Chrysler were lumbered with air pumps, EGR and a whole lot of extra crap and their performance took a real nose dive.

    SO yes .. this is the very simple version

    AS to your situation ... with no vac. retard and if you have set the timing to the factory specs ... your engine is most likely over advanced for most situations.

    My best advice is, unless you have made some major modifications to your engine,trust that all those German BMW engineers really knew what they were doing and to return your engine to the original setup.

    Oh ... and if you are still running the original spark plug leads ... replace them with modern inductive core leads. The original end caps have little carbon rod resistors in them that can crack and cause all sorts of problems.

    Cheers ...

    Graham D
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    hmm .. Wonder what happens if I do this ...

  11. #11
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    Apologies to all for threadjacking!

    Nearly correct - I have the electronic distributor with ignition box on the fender - and no pollution controls.

    Simply the two vacuum lines going to the advance and retard. Someone prior to me brazed over the vacuum switch in the thermostat elbow, and also removed something or other on the intake manifold over the valve cover and plugged it with a pipe plug. I'm assuming it was maybe an air injection system. Also the charcoal canister is missing - with the vent line from the tank just dangling.

    I didn't have much luck finding the proper diagram in the factory manual.

    Going from your description above, im thinking what I need is a new thermostat elbow and vacuum switch. Then manifold vacuum to ignition retard, and ported vacuum to vacuum switch to ignition advance.

    Correct?

    thanks again
    David

  12. #12
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    So I finally went an looked at realoem for these parts, and discovered the vacuum switch is an australia-only thing. Hmm.

    The vacuum switch I found for $40 or so, but the thermostat housing is almost $200

    I'm wondering if my car never had this thing at all, or if whatever it had originally performed the same function in another way.

  13. #13
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    Quote Originally Posted by cgifool View Post
    So I finally went an looked at realoem for these parts, and discovered the vacuum switch is an australia-only thing. Hmm.

    The vacuum switch I found for $40 or so, but the thermostat housing is almost $200

    I'm wondering if my car never had this thing at all, or if whatever it had originally performed the same function in another way.

    Well .. there is a bit of a problem, trusting completely what the RealOEM/BMWFAns/ETK sites say now. Jereon's BMW site posted a warning about 3 years ago basically stating that BMW had "rationalised" their part number cross references for the older models and there were cases of substituted parts not being an exact match anymore. I've noticed that a lot of details in the descriptions of some parts have disappeared as well. They've also changed the format of the lists and I think that might have messed up the listing for the thermo-valves.
    So in the case of the thermo-valve being only specific to the Sweden/Australian models I think that only should apply to the top valve listed with the "80CEL' rating.(that's 80 oCelsius BTW)
    So I'd say the lower listing for the 20/13CEL rating is the normal Euro one. (the 20/13 is the opening closing temp.) I had a look at the parts listings for some of the other models (E12 etc) using the M20 for the same period .. and they showed the 20/13CEL being fitted.

    One thing the RealOEM etc listing does show is a M14 x 1.5 blanking plug to close off the hole if a thermo-valve isn't fitted. Since yours has been brazed over ... that sounds like a later modification.

    You didn't supply any real info on your cars configuration. Was it a grey-market import and went through some sort of "Federalisation" to comply with US emission regs? Is it a manual or auto? Automatics generally have more emissions stuff on them because they usually have to idle at higher rpm. Out here the Autos had an EGR system on them ... that is what the plugged port in the intake manifold is for if it was/is an Automatic.

    I'd simply drill and re-tap the thermostat housing rather than buying a new one. You might find that most of the thread is still there under the brazing. Any competent machine shop should be able to do it fairly cheaply if they don't mind small jobs.

    Cheers
    Graham D
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    hmm .. Wonder what happens if I do this ...

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