2012 Prostar maxforce 13 Cranks but hard to start after sitting

Good Morning
Truck had intermittent problem of randomly shutting down or all engine lights would flash and a beeper would be going off. Been to dealer several times they say can't find anything. Usually driver shuts it down waits a few minutes and good to go. Unit broke down in Baltimore with above symptoms went to dealer they replaced speed sensor. Truck was dropped off at shop for PM driver made comment it was hard to start in AM. Truck sat over night in shop I did notice when changing oil the both location for filters had no oil in the housing . Completed PM truck hard to start could see fuel in Davco filter but did notice oil gauge not moving while cranking. Truck sat over night extremely hard to start . Again fuel showing in Davco filter oil pressure ga. not moving . Not sure if I have a oil pressure issue or maybe a crank sensor or no oil pressure no fuel pressure . Any help appreciated and direction to start . Thanks in advance

 

Thanks Heavyd
I have the truck back. I replaced a couple of the fittings on the fittings at Davco filter housing and at the primer pump. The were correred . Replaced check valve in davco filter it looked ok. Still hard to start ,pumped the primer pump started right up.Could see in the filter at the primer pump very little fuel.So am I looking at a pump and if so . What kinda time to replace it and can it be pulled in and out or does it needed to be timed like and injection pump ??

 

Thanks again Is there any jobs easy on these motors or trucks ? They should make the engineers work on them then you would see some changes . I give you credit I don't know how you could work on them every day. Thanks