New to this forum, but I know this is the Go-To place for me. '05 Duramax 3500 6.6. Was running fine, about to pull out with a loaded trailer when the engine shut off as if I turned the key off. Well, well. Plenty of fuel in tank. Filters full and primed. Not sure now if this has a fuel shut off valve or what ever. Called Chevy dealer and was told it has a regulator. ??? And that it couldn't be tested. ??? And they're very proud of it. And , of course they don't have one. It would have to come straight from GM. I thought that was a fuel shut off valve close to the fuel rail. I took the four screws out and unplugged the wire , cleaned and inspected and re-install. Still not starting. Need suggestions please. I don't want to let it sit at the dealers for a while. That can get expensive and they'll always find something else to tag on. It just seems like it would be something simple.