black box question

I just replaced the fuel pump assembly on my 2001 Astro this weekend. As I was dropping the tank I noticed a small black box mounted on the frame rail with an electrical lead a (2) different sizes of plastic fuel lines running from it to the top of the tank. After lowering the tank, I noticed this large black box mounted to the top of the tank. There were the (2) lines I already mentioned connected to it. Does anyone have any clue what this magic black box is for? My only guess is some kind of interface to the diplay mounted on the overhead console for the fuel milage ect. Fuel pump replacement went fairly well but I could not beleive the pump assembly was $299.00!!!!

When I replaced my pump on a '97, I don't have a black box.
But GM service wanted $860.00 Canadian for it, in a box, not installed. I found an after-market one, best price was $460.00.....

That would be your evaporative canister

Evaporative Emission Hoses/Pipes Replacement - Canister/Fuel Tank
Removal Procedure
Remove the fuel tank. Refer to Fuel Tank Replacement .



Disconnect the EVAP vapor pipe (5) from the EVAP canister (1).
Disconnect the EVAP vapor pipe from the fill limiter vent valve (2).
Remove the EVAP vapor pipe.
Installation Procedure




Connect the EVAP vapor pipe (5) to the fill limiter vent valve (2).
Connect the EVAP vapor pipe to the EVAP canister (1).
Install the fuel tank. Refer to Fuel Tank Replacement .

I found my replacement pump assembly (in the box) at Autozone here and it was $299 US dollars. So you are saying that this rectangular black box mounted on top of the fuel tank is the evaporator canister? Other vehicles have these mounted under the hood to the fender well or firewall:screwy: . This box mounted to my tank has a large ans a small plastic fuel lines with the quick disconnect fittings on it. Both lines run to a smaller black box with a wiring harness attached. Why would an evaporator canister need an electrical connection??? I have the optional computer system in the overhead console that has the compass, fuel milage, and fuel consumption/milage remaining display. This would make more sense to me than the canister. Nothing is wrong with it but I just wanted to find out what the hell it was:rolleyes: .

The description I gave you is a cut and paste from the GM service manual- the diagrams did not paste though, the electrical connections to an evap canister would be for the solenoid valve that can open or close depending on fuel tank pressure or the purge routine. The diagrams clearly show the evap canister mounted on top the tank................

Thanks for clearing up the mystery. My haynes manual did not show anything about this at all so I was a bit puzzled when I started dropping the tank.