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Thread: Test evap system myself before smog test? 1994 e32 740i with M60 engine

  1. #1
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    Test evap system myself before smog test? 1994 e32 740i with M60 engine

    I need to get a smog test and here in California older cars must have the fuel evaporation system tested. Is there a way for me to test this system myself before taking it in? I am assuming I would need at least a vacuum gauge.

  2. #2
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    well, you could check all the valcuum hose, if they are still intact and not broken, the valve is ticking and you can feel that when you touch it by hand, you can also test the ohm, here I posted some testing info https://www.bimmerforums.com/forum/s...ght=evap+valve
    Shogun tricks and tips for the E32 series are HERE!

  3. #3
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    Quote Originally Posted by shogun View Post
    well, you could check all the valcuum hose, if they are still intact and not broken, the valve is ticking and you can feel that when you touch it by hand, you can also test the ohm, here I posted some testing info https://www.bimmerforums.com/forum/s...ght=evap+valve
    Thanks for that. I certainly learned my lesson after that brake assist vacuum hose issue I had.

    I can't discern any ticking with the engine running, which I is what I assume you meant.

    In this post you mentioned that the valve is closed by default and open with voltage:
    https://www.bimmerforums.com/forum/s...0#post19328150

    Does that mean I could do a vacuum test with no voltage applied and either side should hold vacuum? And no vacuum either side when voltage applied?

    By the way, the last time I had the car tested they sold me a new (crap aftermarket) gas cap because they said my cap was defective. Is there a test for the cap? I've since gone back to the original OEM one.

  4. #4
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    Touch the valve with your fingers and then you should be able to sense if it is ticking or not. When engine is at operating temperature, I assume.
    Probably possible the test as you describe it, but never done it before, so it is worth to try a test like that.
    Gas cap testing I have no idea.
    Purge valve: how it works, symptoms, problems, testing https://www.samarins.com/glossary/purge-valve.html
    M60 expert to chime in here.
    Shogun tricks and tips for the E32 series are HERE!

  5. #5
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    Quote Originally Posted by shogun View Post
    Touch the valve with your fingers and then you should be able to sense if it is ticking or not. When engine is at operating temperature, I assume.
    Probably possible the test as you describe it, but never done it before, so it is worth to try a test like that.
    Gas cap testing I have no idea.
    Purge valve: how it works, symptoms, problems, testing https://www.samarins.com/glossary/purge-valve.html
    M60 expert to chime in here.
    Awesome.

    From that link:
    You can find the proper procedure to test the purge valve in the vehicle's service manual. The procedure is different depending on the car make and model. In most cars, the purge valve is normally closed, meaning it should be closed with no voltage and open when the voltage is applied.
    For example, for this vehicle, the service manual recommends applying battery voltage to the purge valve terminals and see if it produces an audible click. We just use a 9-volt battery to illustrate. This purge valve does produce an audible click.
    The next step, as per the service manual for this car is to test if the purge valve closes properly and does not leak. We connect a hand-held vacuum pump and apply vacuum to the purge valve.
    Almost immediately, the vacuum drops. This purge valve doesn't seal properly and must be replaced. This car had a "Check Engine" light on the dash. We had it scanned and got the code P0446 - Evaporative Emission Control System Vent Control Circuit Malfunction. We tested the EVAP system and found that it had a slow leak. Now we found the culprit!

    So the clicking test is a static test and just requires putting 12v to the unit. Nice.
    I have wrenched on vehicles with:

    1 cylinder
    2 cylinders
    3 cylinders
    4 cylinders
    5 cylinders
    6 cylinders
    7 spoke wheels
    8 cylinders

  6. #6
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    I have found a German language info about this system on an E32 735 with DME 1.1, interesting for you, translated this with google http://wp1016621.server-he.de/fotost...DME11-735i.pdf
    see page 3 Tankentlueftung, and it says it starts when the O2 sensor control is active
    Tankentlueftung bei Modellen mit Katalysator
    Die Kraftstoffdaempfe werden ueber einen Aktivkohlefilter, unter Beipischung von Frischluft, dem Motor zugefuehrt. In der Leitung vom Aktivkohlefilter zum Luftsammler befindet sich ein Ventil, das den Entlueftungsstrom abhaengig vom aktuellen Betriebszustand drosselt oder freigibt. Die elektrische Ansteuerung (Taktung) des Ventils erfolgt drehzahl- und lastabhaengig. Der Entlueftungszyklus beinhaltet 16 Taktstufen und beginnt, sobald die Lambdaregelung aktiv ist. Nach Ablauf eines Zyklus erfolgt die Schliessung des Ventils fuer circa 5 Minuten. Im stromlosen Zustand ist das Ventil nur durch Rueckschlagventil verschlossen. Bei steigendem Unterduck im Luftsammler wird das Ventil geoeffnet, solange keine 12V Spannung anliegt.

    Tank ventilation on models with catalytic converter
    The fuel vapors are supplied to the engine via an activated charcoal filter, with the addition of fresh air. There is a valve in the line from the activated carbon filter to the air collector, which throttles or releases the ventilation flow depending on the current operating state. The electrical control (timing) of the valve is speed and load-dependent. The vent cycle includes 16 pulses and begins as soon as the lambda control is active. After one cycle, the valve closes for approximately 5 minutes. When de-energized, the valve is closed only by the check valve. As the pressure in the air collector increases, the valve is opened as long as there is no 12V voltage.


    then see page 13, Testing tank breather valve

    Tankentlueftungsventil (TE-Ventil)
    Das TE-Ventil wird im Sekundentakt angesteuert. Die Taktung ist mit der Hand fuehlbar.
    Dichtheit pruefen: Unterdruckversorgung vom Service Tester am 8mm Anschluss anschliessen. Durchflusspfeil beachten. Unterdruck auf 600 mbar einregulieren und TE-Ventil mit 12V versorgen. Unterdruckpumpe abschalten, nach 20 Sekunden darf der Druckabfall 50 mbar nicht uebersteigen. Im stromlosen Zustand ist das TE-Ventil durch ein Rueckschlagventil bis zu einem Saugrohrunterdruck von 20 mbar geschlossen.
    Ansteuerphasen pruefen: Das TE-Ventil wird im Leerlauf angesteuert und ist somit geschlossen. Sobald die Lambdaregelung aktiv ist und die RPM bis auf circa 1600 erhoeht wird, kann die Schrittweise Oeffnung beobachtet werden.

    Tank ventilation valve (TE-valve): The TE valve is activated every second. The pulsation can be felt by hand.
    Check for air leaks: Connect the vacuum supply from the service tester to the 8 mm connection. Note the flow arrow. Adjust negative pressure to 600 mbar and supply TE valve with 12V. Switch off the vacuum pump, after 20 seconds the pressure drop must not exceed 50 mbar. When de-energized, the TE valve is closed by a check valve up to a suction pipe vacuum of 20 mbar.
    Check activation phases: The TE valve is activated in idle and is therefore closed. Once the lambda control is active and the RPM is increased to about 1600, the stepwise opening can be observed.
    Last edited by shogun; 12-11-2019 at 09:26 PM.
    Shogun tricks and tips for the E32 series are HERE!

  7. #7
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    Quote Originally Posted by shogun View Post
    I have found a German language info about this system on an E32 735 with DME 1.1, interesting for you, translated this with google http://wp1016621.server-he.de/fotost...DME11-735i.pdf
    see page 3 Tankentlueftung, and it says it starts when the O2 sensor control is active
    Tankentlueftung bei Modellen mit Katalysator
    Die Kraftstoffdaempfe werden ueber einen Aktivkohlefilter, unter Beipischung von Frischluft, dem Motor zugefuehrt. In der Leitung vom Aktivkohlefilter zum Luftsammler befindet sich ein Ventil, das den Entlueftungsstrom abhaengig vom aktuellen Betriebszustand drosselt oder freigibt. Die elektrische Ansteuerung (Taktung) des Ventils erfolgt drehzahl- und lastabhaengig. Der Entlueftungszyklus beinhaltet 16 Taktstufen und beginnt, sobald die Lambdaregelung aktiv ist. Nach Ablauf eines Zyklus erfolgt die Schliessung des Ventils fuer circa 5 Minuten. Im stromlosen Zustand ist das Ventil nur durch Rueckschlagventil verschlossen. Bei steigendem Unterduck im Luftsammler wird das Ventil geoeffnet, solange keine 12V Spannung anliegt.

    Tank ventilation on models with catalytic converter
    The fuel vapors are supplied to the engine via an activated charcoal filter, with the addition of fresh air. There is a valve in the line from the activated carbon filter to the air collector, which throttles or releases the ventilation flow depending on the current operating state. The electrical control (timing) of the valve is speed and load-dependent. The vent cycle includes 16 pulses and begins as soon as the lambda control is active. After one cycle, the valve closes for approximately 5 minutes. When de-energized, the valve is closed only by the check valve. As the pressure in the air collector increases, the valve is opened as long as there is no 12V voltage.


    then see page 13, Testing tank breather valve

    Tankentlueftungsventil (TE-Ventil)
    Das TE-Ventil wird im Sekundentakt angesteuert. Die Taktung ist mit der Hand fuehlbar.
    Dichtheit pruefen: Unterdruckversorgung vom Service Tester am 8mm Anschluss anschliessen. Durchflusspfeil beachten. Unterdruck auf 600 mbar einregulieren und TE-Ventil mit 12V versorgen. Unterdruckpumpe abschalten, nach 20 Sekunden darf der Druckabfall 50 mbar nicht uebersteigen. Im stromlosen Zustand ist das TE-Ventil durch ein Rueckschlagventil bis zu einem Saugrohrunterdruck von 20 mbar geschlossen.
    Ansteuerphasen pruefen: Das TE-Ventil wird im Leerlauf angesteuert und ist somit geschlossen. Sobald die Lambdaregelung aktiv ist und die RPM bis auf circa 1600 erhoeht wird, kann die Schrittweise Oeffnung beobachtet werden.

    Tank ventilation valve (TE-valve): The TE valve is activated every second. The pulsation can be felt by hand.
    Check for air leaks: Connect the vacuum supply from the service tester to the 8 mm connection. Note the flow arrow. Adjust negative pressure to 600 mbar and supply TE valve with 12V. Switch off the vacuum pump, after 20 seconds the pressure drop must not exceed 50 mbar. When de-energized, the TE valve is closed by a check valve up to a suction pipe vacuum of 20 mbar.
    Check activation phases: The TE valve is activated in idle and is therefore closed. Once the lambda control is active and the RPM is increased to about 1600, the stepwise opening can be observed.
    Excellent info, bookmarked for future reference. My car failed the smog test, though the evap system did pass. I will be going back for a retest today.
    I have wrenched on vehicles with:

    1 cylinder
    2 cylinders
    3 cylinders
    4 cylinders
    5 cylinders
    6 cylinders
    7 spoke wheels
    8 cylinders

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