How does the secondary diaphram work?

Discussion in '40- & 55-Series Tech' started by GreenFJ40, Nov 15, 2005.

  1. GreenFJ40

    GreenFJ40

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    Does the secondary diaphram rod "pull" the secondary throttle plate open OR does it just allow the secondary to open via a spring load under vaccuum?
    Just wondering if mine is hooked up right, I can reach down there with the engine off and pull the rod freely without the secondary moving, understanding that with the peddle not depressed it prevents the secondary from opening.
     
  2. RHINO

    RHINO

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    oh man,,, trying to remember. seems like when i was rebuilding mine and playing with the secondary it "allowed" the valve to open. i remember i put vacuum to it and watched it move to make sure it was working.
     
  3. Robert LaDuke

    Robert LaDuke

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    Yes, it is vaccum operated. Also can't be seen operating unless the truck is moving from what I recall.
     
  4. GetsUThere

    GetsUThere

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    IIRC the linkage is set up such that the secondary doesn't engage to pull open until the primary is partially open.
     
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