Need I picture from 96 or 97 5.7l and some input

[SunlitComet]

This is in regards to the evaporator emmisions canister purge vacuum switch located between the right valve cover and throttle body mounted on the upper intake section with a blue connector on it. It has the connection to the canister and purge solenoid. However there is a third connector that points to the fender with a rubber elbow. My data shows it not to be there and the gm picture database show it to be the elbow with a part #. If it is just a vacuum switch I can understand two ports so it can be mounted in between two components in this application but why a third port, why a rubber elbow and finally why does this elbow om my truck have a damn bolt in it. Can not find tech design info on the switch itself so I have no idea if it it a dead unused port in the specific application and I am sure this is not something the factory would do. Why not a rubber cap? Possibly some vent (kills the intended use I think). I included some pictures to demonstrate what I am seeing. I would like to to pics from other vehicles to compare what I should have hear or any input from others. If my data is incorrect I need to know. This vehicle was built with the federal emmisions standard but I am sure it would apply to cali as well.

 

[steamroller]

Take the bolt out, it's supposed to be open. I wondered about the same thing when I replaced the injectors 4-5 yrs ago and after looking at several and going through as many pics online I could find they were all that way. I found this which sort of explains how it works. I'm guessing it pulls some outside air in through that elbow

The gas tank is sealed to the atmosphere. There is a vent line from the tank leading to a small black canister mounted underhood near the driver-side headlight. This canister is full of activated carbon, which absorbs fuel vapor. As the tank heats up and the vapors inside expand, they exit the tank through the vent line and enter the EVAP canister. The hydrocarbons in the fumes are then absorbed by the activated carbon, and the remainder of the vapors exit the canister through a vent port. When the engine is running at a constant speed, a valve called the EVAP purge valve opens, and applies intake vacuum to the EVAP canister. This sucks air in through the vent port, across the activated carbon, and into the engine. This removes the hydrocarbons that were stored in the carbon and burns them in the engine.

 

[SunlitComet]

I was planning to but I get my diagnosis hard/software soon and plan on getting data dump
snapshots of the vehicle as each repair is done I am am holding off starting for a few more days becuase I would like a snapshot of the condition I got the truck in.

I now about the evap system. The problem with this switch with the bolt is that its purpose is to report a vacuum of 1in hg or more. Like a feedback signal to indicate if a task is taking place or not and the pcm can respond accordingly. With that said they could have use a one port switch and tee'd it in. I think I know why they went this direction. I think they were intending to create a small leak to allow the switch to respond properly with the right sensativity. Like a diaphram switch where one side is vented. Just seems a little big for a diaphram vent. Probably to make sure typical debris and fluids that build up do clog it to easily. That is the route I am taking so far just wanted some data to back it up. one of the previous users probably could not figure it out and thought it would be better plugged.

Thanks

 

[steamroller]

No problem man. It is odd the way they did but I guess they must've had some reason for it. I guess just to make it more complicated than it had to be.

 

[longstand]

Here is some picture, i dont see what your looking for.. maybe because my Car is a Denali and its a 1999

but here some picture

 

[SunlitComet]

Thanks longstand but you are right yours is a '99.
I would need pictures of a '96 or '97 tahoe or yukon. '99's dont use that part.

 

[longstand]

Anyone? I know someone has a 1997 and older Yukon here, go out and take a picture LAZY S.. LOL

Help a Brother OUT!!!

 

[SunlitComet]

No problem man. It is odd the way they did but I guess they must've had some reason for it. I guess just to make it more complicated than it had to be.

Was likely what was available for production use in those model years that used it.

 

[96ProCompTahoe]

if i remember tomorrow at work (and have a free moment) i'll snap a picture for you on my 96. i'd do it now, but its dark.

 

[brooks93]

96 tahoe 5.7L