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308 Cut Off Valve Replacement

Discussion in '308/328' started by lou staller, Jan 9, 2020.

  1. lou staller

    lou staller Formula Junior

    Dec 21, 2002
    378
    Orange County Ca
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    Lou Staller
    I've searched the parts cross reference sticky and searched for an alternative cut off valve for my 308 QV but didn't find any new threads with any updates. I saw that there were alternative valves from a Saab or early GM cars but couldn't find any of them being available. Does anyone have info on a valve that might still be available? Thanks!
     
  2. Rifledriver

    Rifledriver Two Time F1 World Champ

    Apr 29, 2004
    26,142
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    Brian Crall
    #2 Rifledriver, Jan 9, 2020
    Last edited: Jan 9, 2020
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  3. Steve Magnusson

    Steve Magnusson F1 World Champ
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    Jan 11, 2001
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    121751 original
    147390 superseded
    (Just adding the F PNs for future searches - and the superseded one looks very much like the parts Brian posted.)
     
  4. lou staller

    lou staller Formula Junior

    Dec 21, 2002
    378
    Orange County Ca
    Full Name:
    Lou Staller
    Yes, the air injection shut off valve. While doing something in the engine compartment I noticed the small hose was not on the top of the valve. The plastic nipple was broken off and in the end of the hose. I'm going to take the valve off to see if I can repair the valve by possibly replacing the plastic nipple with a small piece aluminum pipe. If it turns out to be too weak I'll just buy a replacement, now that I have the replacement part info. Thanks so much!
     
  5. miketuason

    miketuason F1 World Champ
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    Feb 24, 2006
    13,413
    Cerritos, CA.
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    Mike
    What and how exactly this shut off valve works on a QV, and does the small fitting on top of the valve create vacuum while the engine is running? I tried to blow and suck air from it but the air just goes through and no vacuum when the engine is off.
     
  6. Steve Magnusson

    Steve Magnusson F1 World Champ
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    #6 Steve Magnusson, Jan 15, 2020
    Last edited: Jan 15, 2020
    No, the way it should work is that when vacuum is applied to the small fitting (via the electrovalve during cold-running) the cutoff valve should be open allowing the exhaust pulses to draw fresh air (in the direction of the arrow) into the exhaust stream. During warm-running, no vacuum is applied to the small fitting so the valve is closed and no fresh air enters the exhaust stream.

    If you blow in the direction of the arrow on the cut-off valve (with no vacuum on the small fitting), and air flows = the cut-off valve is bad (and a bad cutoff valve will muck up the Lambda operation).

    However, the cut-off valve is not designed to prevent flow if you blow against the direction of the arrow (i.e., in that direction, even a good valve can be "blown" open).

    Another test would to blow (or suck) into the small fitting -- the chamber that it connects to should be always fully sealed. If you get a sustained airflow = confirms the diaphragm inside is broken.

    There is a good figure (Fig. 77) showing the internal construction of the cut-off valve on page D100 of the TR WSM if you have access to a copy.
     
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  7. miketuason

    miketuason F1 World Champ
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  8. Steve Magnusson

    Steve Magnusson F1 World Champ
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    Jan 11, 2001
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    Yes (but airflow only occurs during cold-running -- i.e., only when the water thermoswitch is cold/closed = energizes electrovalve = puts vacuum onto the small fitting of the cutoff valve = opens cutoff valve).
     
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  9. Rifledriver

    Rifledriver Two Time F1 World Champ

    Apr 29, 2004
    26,142
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    Brian Crall
    That valve is a big reason the check valves should be replaced at services. They get rusty, then leak and the leakage of exhaust gas back up the hoses cooks the hoses and melts the shut off valve. Check valves should be a standard service item.
     
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  10. miketuason

    miketuason F1 World Champ
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    Feb 24, 2006
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  11. Lawrence Coppari

    Lawrence Coppari Formula 3

    Apr 29, 2002
    1,873
    Kingsport, TN
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    Lawrence A. Coppari
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  12. Rifledriver

    Rifledriver Two Time F1 World Champ

    Apr 29, 2004
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    I quit using off brand valves years ago. Had too many prematurely fail and burn up a bunch of expensive parts upstream. I use only Delco branded now.
     
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  13. johnk...

    johnk... F1 Veteran
    Owner

    Jun 11, 2004
    7,576
    New England/FL
    Is that entire air injection system even necessary? Isn't it just an emissions thing?
     
  14. Rifledriver

    Rifledriver Two Time F1 World Champ

    Apr 29, 2004
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    Only if you like clean air.
     
  15. johnk...

    johnk... F1 Veteran
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    Jun 11, 2004
    7,576
    New England/FL
    But doesn't it shut off once the car get up to temperature? Isn't it just to help get the cat up to temp quickly?

    Image Unavailable, Please Login

    Clean air? I doubt that all the Ferrairs evey made have produced as much air polution as one year's production if Honda Civics. :)
     
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  16. Rifledriver

    Rifledriver Two Time F1 World Champ

    Apr 29, 2004
    26,142
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    I am more than a little surprised you don't know what it does.

    Sorry but I grew up in a California that had post apocalyptic air. We had time outs between plays in major league games so players could breath bottled air. I think automotive smog control, especially totally passive items like this are good.

    If you really don't care its fine with me but the sooner you quit driving the better off we'll be.
     
  17. johnk...

    johnk... F1 Veteran
    Owner

    Jun 11, 2004
    7,576
    New England/FL

    I didn't say I don't care. I just made an observational comment that (polution/mile) x miles driven is the more relavant number. In any case, I'm not one who has tampered wit the emissions controls on my cars. My cars, when required, always pasted the sniff test in CT, and presumably would today, though CT doesn't require testing for cars 25 yrs ol dor more.
     
  18. dwhite

    dwhite F1 Rookie

    My airpump was removed by the original owner in 1983 on my 308QV, which I acquired in 2001. I passed emissions every year in Long Island, NY, when it was required.

    Texas only tests for emissions in 17 counties, great place for the rest of us who want to breathe clean air. Florida does not inspect for safety or emissions, so all this BS about concerns for air pollution is a joke.
     
  19. thorn

    thorn Formula 3
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    Aug 7, 2012
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    Tallahassee, FL
    *Waves from Florida*
     
  20. dwhite

    dwhite F1 Rookie

    Yep, I have a place in vero beach and we just registered a 2015 mini there for my wife. Nothing, nada.

    Hey, maybe that's why no one signals when turning, the signals don't work and they don't know. ;-)
     
  21. Lawrence Coppari

    Lawrence Coppari Formula 3

    Apr 29, 2002
    1,873
    Kingsport, TN
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    Lawrence A. Coppari
    No vehicle inspections in Tennessee either.
     

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