[ArnoldRC]

Have you ever tried to cycle the key for a few seconds a few times when you think the issue may occur? I know you said if it sits a few weeks it's fine, but is that set in stone? Sometimes the check valve in the fuel system goes bad, and it can take a little while pressurize the fuel rails, resulting in extended crank times. Cycling the key will prime the system up.

 

[ArnoldRC]

That being said I'm sure the valve is working. Does your truck have twin tanks?

 

[ArnoldRC]

Do you ever notice any fuel transfer between tanks?

 

[ArnoldRC]

Do you suppose the issue is problematic only when using one specific tank? Or does it do it no matter which tank you've selected?

 

[ArnoldRC]

Sounds like the switch valve is leaking.