I just this truck from a guy, it has been sitting for quite awhile, front tank fuel pump does not work, he said you can just run it off the rear tank. It has worked for a couple weeks, now it won't start. Rear pump runs, but truck does not get fuel. I replaced the fuel filter, there was pressure in the line when I pulled it off. Truck will pop when you spray starting fluid into the intake, but will not stay running. I am wondering if the fuel pressure regulator is bad, what do you think?