Anyone having trouble with fuel shut off valves on 2000 Blazers? I have 3 and 2 of them quit working. Took them apart and it seem they work ok but...

Talked to my mechanic and he said that he has replaced quite a few in the last few months, but hasn't taken the time to find the problem.

I'm getting 3 new ones under warrenty.

Checked them with air and have the valve definately in the right position.

Any inputs?

Had a 325 Mag. with the hoses hooked up backwards between the on and reserve. Could your lines be switched between the tank and on? Service manuel has diagram with proper routing

This shutoff bolts directly onto the bottom of the tank. No chance of hoses being reversed. Had them both working until a guy wanted to buy one of the ones that I work on. From the barn to the truck it died. I've got new ones at the dealer and he is going to get one. The whole valve is about as simple as you can get. Doesn't make sense. I've worked on $100,000 machines that were hydraulic and the valving was much more complicated and problems could be diagnosed and fixed. But this one...