I'm sure the answer is already here somewhere but can someone give me a hint as to how the switch at the pump works? With 2 vacume lines running to it from the adjustable controller switch at the manifold. What happens when it is not connected specifically do to one of the vacume ports broken off, does it cause the pump to go to full pressure or low pressure? And has anyone figured a way to bypass it all together and put and adustable switch at the pump itself to maintain a specific pressure?

 

Does'nt change the pump pressure at all, except very slightly as engine revs change.

What the 'switch' does is raise the engine idle slightly when the steering gear is turned to lock and the pump is working against maximum load.

This idle-up is supposed to avoid engine stalling during this extra loading of the PS pump.

Many folks can't tell the difference whether this idle-up is working or not.

You really don't need it at all.

 

10-4,Thanks for the reply!
Somewhere along the line I understood it to increase pressure at low speeds (high vacume) like crawlin or idling around the hills and to decrease pressure at high speeds (low vacume) like cruzin / fuel economy. But 2 lines to the switch led me to think that maybe it "throttles itself" and the adjuster lets you fine tune it. Mine broke a line at the switch on the pump somewhere along the line and now I seem to have fluid leaks at the box and pump leading me to believe its full throttled the pump. I'm no Yota scientist but was thinking of attempting some sort of adjuster at the pump switch and do away with all the other scientifically designed stuff. And then again I could just replace it and move on to some other project the old lady would prefer me to do or leave it and ignore the leaks.

 

The leaks at the box and pump don't have anything to do with the throttle-up valve. (Unless of course its the t-u valve itself thats' leaking.)

Just coincedental.

Maybe your truck is like 'The Wonderful One Hoss Shay'-- built so perfectly that no part wore out before the other one, and everything failed at once.

 

OK I'm over that contraption and now am wondering why there is a second smaller vacume line to the fuel pressure regulator from one of the gizmo switches on the fenderwell, what does it do to the regulator? I seem to think that at one time I found an article explaining the gizmo switches in detail but cannot find it.

 

Fuel Pressure-Up system. When the engine is hot (and subject to vapor lock), the ECM opens the VSV, which connects the FPR vacuum line to atmosphere, which raises the rail pressure briefly to overcome any vapor lock.

http://web.archive.org/web/201503060...ne/99fuelp.pdf

 

Thank you very much, I appreciate the answer and attachment.

 

The term "one-hoss shay" is used to describe depreciation, in which a durable product delivers the same services throughout its lifetime before failing with zero scrap value. A Toyota is a common example of such a product and an excellent name choice, Thanks!

 

Um, it's actually a beloved poem by Oliver Wendell Holmes. The actual title:

The Deacon's Masterpiece or, the Wonderful "One-hoss Shay"

http://rpo.library.utoronto.ca/poems/deacons-masterpiece-or-wonderful-one-hoss-shay-logical-story

Your basic interpretation of that cultural reference is, IMO, correct.

 

Logic is logic. That's all I say!