Alpine951

Been trying to track down what seems to be a big vacuum leak. I deleted the venture years ago. Just got myself a mightvac . This part sits along the drivers side (Merica) fender. The tip of the screwdriver is resting against it. There are 3 ports coming out of it. One goes to that black round diagphram. The black diagphram has a vacuum line that goes to a part that sits under the back side of the intake manifold that has 2 nipples with vacuum hoses. Not sure what that is for. If I disconnect the vacuum line for the black diagphram at the part under the manifold and put some vacuum to it, it won't hold vacum. Then I move to the vacuum line that comes out the top part of this metal part in the picture, which runs to the intake manifold, hook up the tester and it won't hold any vacuum as well. There is a third port on this part that is partially hidden in the picture that runs to the MAF pipe. I check that line and it also won't hold vacuum.

Should any of these three hold vacuum?

rlm328

It is part of the gas tank vapor recovery system. And yes it is vacuum operated.
You really need to clean that engine bay.

Tom M'Guinn

The metal valve with the screwdriver pointing to it should hold vacuum. I'm not entirely sure which other lines you are testing, but to test this system for big leaks, try temporarily plugging the port/hose at the j-boot and see if your vacuum goes up and/or if the car runs better.

divil

The bigger plastic one should hold vacuum too, where the small hose attaches. I think it is mechanically the same as the blow off valve in the intake - a spring holds it closed, and vacuum pulls it open via a diaphragm.

You can read a good explanation of how it works here.

Alpine951

I unplugged the three lines and plugged them up. no difference. Dam...