How does the secondary diaphram work? (1 Viewer)

[GreenFJ40]

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.

 

[RHINO]

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.

 

[Robert LaDuke]

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

 

[GetsUThere]

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