I have an 88 c2500 scottsdale, 2x4, 350, 5-speed. It does not always get fuel to the throttle body, but it does occationally. When it does it runs like new. It has a new pump and filter. The pump runs when i turn the key but fuel doesn't spray into the intake. I disconnected the fuel line from the throttle body and trust me, ther is fuel in the lines. the truck has left me stranded many times. What could be wrong?