VilleJKL

Temp switch vacuum hose should be connected to this, right? I tried to blow through this, but it feels completely blocked. Is there somekind of mechanism behind it?

V2Rocket

there is a tiny port drilled inside the ambient pressure side of the throttle body on the other side of that barb.

VilleJKL

Thanks. So actually it's not vacuum connection at all. Could you explain how the vacuum system is supposed to work? Thermo valve is connected to some sort of vacuum valve that is connected to fuel vapor control valve. This is relevant because I'm running ITBs and would like to have the charcoal canister working "as stock".

VilleJKL

I used this thing called the google and found out:

"The EVAP system prevents fuel vapor from the fuel tank from leaking into the atmosphere. It consists of four parts. 1) The vapor canister, which accumulates vapor from the fuel tank. 2) The plastic EVAP shut-off valve (CVI), which momentarily opens, only when the engine is hot, to purge the vapor canister of accumulated vapors. 3) The metal EVAP control valve (CVII), which controls the vapor flow rate when CVI is open. 4) The temperature controlled vacuum switch (Thermo Switch), which activates the EVAP system only when the engine is hot.

The vacuum canister is located in the wheel well on the driver's side. The two valves (CVI & CVII) are located in front of the brake booster next to the fluid reservoir on the inner fender. The temperature controlled vacuum switch (Thermo Switch) located in a small coolant line under and between intake runners 3 & 4.

The 2-1/2" plastic valve (actually a vacuum operated check valve) is called the evaporative emission shut-off control valve (CVI). The inlet to this check valve connects to a tee which connects to both the fuel tank vapor line and the vapor canister. That is how excessive fuel tank vapor pressure is accumulated and condensed in the vapor canister. The motive force for CVI is through the vacuum line that goes to the Thermo Switch. The Thermo Switch has two nipples on it. One points up and the other one points up at an angle. The vacuum line from CVI goes to the nipple that points up. The nipple that points up at an angle connects to the upstream throttle body nipple that points forward at an angle. (Angled nipple to angled nipple.)

The job of CVI is to momentarily purge the vapor canister to the engine when: (1) the engine is hot via the Thermo Switch. And (2) the throttle plate just comes of idle when vacuum is momentarily high upstream of the throttle plate. After that moment, at part throttle or WOT, there is not enough vacuum to keep CVI open. Hence, if the vacuum line from CVI is disconnected, CVI "should" always be closed.

The 2-1/2" metal valve bolted to the inner fender is the evaporative emission flow control valve (CVII). The job of CVII is to regulate the vapor flow rate, through CVI, to the intake manifold via the j-boot. The motive force for CVII is through the vacuum line that goes to the downstream throttle body nipple that is shared by the Fuel Pressure Regulator and Fuel Pressure Damper."
- onZedge @ PelicanParts


So it might be impossible to mimic the original beatifully mechanical action with itbs. If I want the charcoal canister to work I would need electrical valve and control it with ECU.