Check the following
1- The fuel run relay and fuse in the PDM (fuse box) swap the relay with an other relay. Or check for voltage at the fuel regulator lock off but this will take two people. Battery voltage is regulated so with the key on and the engine not running the battery voltage to the regulator will time out. You can also try starting fluid to see if the engine will fire off but be careful. If the engine fires off then the issue is in the fuel system if not continue with the following.
2- Check the LP mixer diaphragm. Make sure it isn't dirty, torn or hard.
3- Replace the crank sensor located at the bottom of the timing cover. The VSM must read 150 RPM before the engine will start up and run. In saying this also make sure the battery is charged and in good condition as well as the starter operating properly and not dragging.