I need to know what it is ......

Yesterday I hit a rock and it bounced up and hit something under the drivers side of the van. Just behind the drivers seat. The part it hit is now hanging down. It looks like a small piston of some sort. It black with a metal rod coming out of it with a black rubber piece on the end. I looked under and see where it hooks in the underside and I'm able to push the end with the rubber piece back in the bracket. But what I need to know is what is it and I'm I in any danger if this thing keeps poping out.. Help please.

What year is your van?

Sounds to me like it's the Evap Leak Detection Pump Solenoid... at my local dealer it's a $135.00 part...

What is it..

There is a line that leaves the gasoline cap that runs to it. It collects all the fumes in it and there is a solenoid under your hood located in the front left side that at about 45 MPH tell it to release the fumes to the engine and burn them up (Use them as fuel)

How do I know this look up my post:
http://www.automotiveforums.com/vbulletin/showthread.php?p=1129866#post1129866

Your CE light may come on with the Diagnostic Trouble Code FP1495.

That is NOT a Major issue you can continue to drive your van like this as it will not harm your catalytic or anything else for that matter. (according to the error I had)

Again this is just my guess as I had that issue on my other thread and that is where the canister is located on my 97 GC