1985 diesel after sitting overnight will not start
The check valve is a small brass fitting where the return line attaches to the filter head. I believe it takes a 7/16" wrench. There is a 'duck bill' inside that prevents fuel from leaking back to the tank causing air in the system. It should allow flow in only on direction. Some times you can see light through it if it's bad enough. Also, the lines between the injectors can dry out and start to leak air. Air will leak in before fuel leaks out, and you won't see it. There are plastic, cup-shaped connectors for these hoses that press onto the top of each injector. They are sealed by two o-rings on each injector body where it meets the connector. These o-rings can dry out and also leak air and fuel. Your Ford dealer or diesel service professional should have the proper o-rings. Any other o-rings might not seal, as they won't be the exact size. You already changed the fuel solenoid when you replaced the pump. It is inside. There has to be battery cranking voltage to it while cranking, and battery voltage with key in 'on' position. The wire attaches to the top of the pump. This is not likely to be the problem, since it restarts every 2 hours.
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