Hi.

If my '97 XLT (4.0 OHV) sits for a day or two it has trouble starting. It cranks fine but does not seem to be getting fuel. I can hear the fuel pump pressuring up the system when I first turn on the key. If I keep cranking the engine sooner or later it will start. When it does start it runs a little bit rough for a few seconds then runs fine. It seems to have more trouble when parked slightly uphill than when parked slightly downhill.

I'm suspecting that perhaps there is a check valve somewhere and the fuel is slowly draining back into the gas tank. I cannot find any check valve in any diagrams (I have the Ford service manual on CD). Is it built into the fuel pump?

Any ideas what else would cause this? Thanks.