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Here’s the pic. The IWE line tees of the main line going to the brake booster.
I can't be completely positive, but that looks similar to what is on the 2nd gen 3.5. That hose coming off the intake is under vacuum of course when the engine is idling, sometimes at low loads. When it goes positive because of boost, the checkvalve in the IWE line closes. The manifold pressure produces flow thru a venturi in that collection of hoses/lines, and produces vacuum. The outlet side is piped to the clean air line after the air filter some where. That system is called "ActiVac", and is made by Dayco. Do a search, and you can find it. They really haven't let loose with a lot of info, but with my experience in power plants, both marine and stationery, I pieced it together. In industry, that's what would be known as an air ejector, or an eductor.
That setup takes the place of a vacuum pump.
Almost. When the solenoid is energized, the vent is closed off, and vacuum is allowed to the IWEs. When it is deenergized, vent opens, and bleeds off vacuum, and closes vacuum to IWEs. It's a little spool valve that moves up/down inside the solenoid.
IWE solenoid I cut apart, sliver object is the "spool" valve. Not a true spool valve, but I don't know what else to call it.
I have it backwards? So you're saying; When the solenoid deenergizes, vent opens to bleed off vacuum but closes vacuum to the IWE actuators? Just one question: What vacuum is being bled off from where if it's closing vacuum to the IWEs'?
What I thought venting to be and mean was the releasing (venting) of the vacuum that was held at the actuators, allowing them to spring back into 4WD engagement with the hub. I'm confused here on what's being vented when the solenoid is deenergized.
T or F to this statement: To turn on 4WD, the solenoid gets energized.
I have it backwards? So you're saying; When the solenoid deenergizes, vent opens to bleed off vacuum but closes vacuum to the IWE actuators? Just one question: What vacuum is being bled off from where if it's closing vacuum to the IWEs'?
What I thought venting to be and mean was the releasing (venting) of the vacuum that was held at the actuators, allowing them to spring back into 4WD engagement with the hub. I'm confused here on what's being vented when the solenoid is deenergized.
T or F to this statement: To turn on 4WD, the solenoid gets energized.
That's a false. The default for this system, in case of vacuum loss for whatever reason, is the IWEs are engaged.
When power is lost to the solenoid when shutting off the truck, or switching to 4A, 4H, or 4L, that little valve falls downward with spring assist, closing the vacuum supply port, and opening the vent port, venting the vacuum to atmosphere, therefore engaging the IWEs.
That's only the vacuum in the lines to the IWEs, and the IWEs themselves.
Last edited by johnday in BFE; Jan 29, 2021 at 07:44 PM.
That's a false. The default for this system, in case of vacuum loss for whatever reason, is the IWEs are engaged.
When power is lost to the solenoid when shutting off the truck, or switching to 4A, 4H, or 4L, that little valve falls downward with spring assist, closing the vacuum supply port, and opening the vent port, venting the vacuum to atmosphere, therefore engaging the IWEs.
That's only the vacuum in the lines to the IWEs, and the IWEs themselves.
