That's absolutely correct, FM!
ANY leaks in either the suction side plumbing to the lift pump, between the lift pump and the injection pump, or leaks at the injection pump itself (at the throttle shaft, for example) or in the fuel return system will let air in after shutdown and make for hard starting/extended cranking.
SMP and others sell kits with O-rings for the top of the injectors and the plastic return fittings that fit over them, along with lines and clamps.
I've also seen the fuel heaters in the filter "head" leak, and some have water separators on the firewall towards the LH fender that can develop leaks and let air into the system.