Parked up for the weekend - No Start

[merv dessent]

2000 F350 Flat Bed 7.3 PSD - Parked up Truck on Friday afternoon.
No start on Monday morning.
Engine turned over good, plenty of power from batteries.
Gave it short bursts from starter motor and on 5th attempt engine started fine, back to normal
Seems like air leak on fuel injection system.
No symptions before and all maintenance up to date.
Plenty of new oil and fuel filter new.
This engine always starts come rain or shine or snow.
I was thinking either O ring on filter housing or hpop lines.
There are no external oil/ fuel leaks
Anyone had similar problem?