TR Differential Pressure switch...????

Discussion in '308/328' started by carguy, May 18, 2005.

  1. carguy

    carguy F1 Rookie

    Oct 30, 2002
    Alabama (was Mich.)
    Full Name:
    In my quest to get all the "bugs" out of my TR, I would appreciate if someone could tell me about the differential pressure switch, and it's associated plumbing. This is that little vacuum cannister with the wires connected to at the front/top area of the right rear inner fender. There is a vacuum hose coming from the right side intake plenum, that connects to a "T" fitting and then there are two short hoses from the "T" that go to the switch. The switch has 3 ports, but I only have two hoses plugged onto one port is "open". I would like to verify this thing is hooked up properly and working. Any help is appreciated.....Thank You; Jeff
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  3. Steve Magnusson

    Steve Magnusson F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    Full Name:
    Steve Magnusson
    #2 Steve Magnusson, May 18, 2005
    Last edited by a moderator: Sep 7, 2017
    Does this mean that you failed the cold-running "blip" test?

    Don't confuse the electro-valve controlling the valves on the air injection system with the differential pressure switch (even though it's all mounted in a single lump). I believe the figure on page 72 of the '89 or '91 TR US OM shows it correctly (and I'm going from memory so I'll correct anything I mangle later):

    The vacuum line from the 1/6 intake plenum is "T"ed into 2 streams -- one goes to the single fitting on the differential pressure switch and the other goes to electrovalve fitting #1 in the jpeg (the picture is from a different F application so the hose hook-ups are different) -- the end of the electro-valve that has two fittings. Another vacuum line runs from electrovalve fitting #2 (sticking up on the electro-valve) to the air injection system control valves, and the (single) fitting #3 on the other end of the electro-valve is open to atmosphere.

    Essentially all you need is that the fitting on the differential pressure switch is (always) connected to the 1/6 intake plenum vacuum.
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