98 chevy astro van (164k) won’t start after sitting all night. If I cycle the fuel pump 3 times it will start. I can drive it for 500 miles or I can leave it off for 3-4-5 hrs and it will start. Sometimes it runs a little rough when I first get it started. Is there a leak that lets fuel drain out and air get in or is it the fuel pump? (Does it whether parked up hill or down hill)
There may be check valve in the pump that is allowing fuel to leak back into the tank. You may want to have the fuel pressure checked.
The problem most likely is the check valve in the fuel pump assembly is defective.
This check valve prevents the fuel in the fuel rail(s) and line from draining back into the gas tank when the vehicle sits idle for an extended periods of time.
When you cycle the ignition switch enough times, this cycles the fuel pump to where it’s able to reprime the fuel system, and the engine starts.
A new fuel pump assembly will fix this problem.