Is it air in my 617 fuel system?
 

Last weekend, I noticed that my 300sd lacks power on uphill climbs. When I got home, I checked the pre-filter and found out that it is clean and it is the primary pump that is the culprit. After replacing the it, I forgot to hand-pump and directly cranked it. I just noticed that I have to prime it first using the hand pump and so I did. My engine started and the power problem was fixed.

The next day, i started it but it took about 5 to 6 seconds of cranking before it starts. This is the first time it happened to me and I suspect that maybe some air is still in the system when I forgot to hand pump it when I replaced the filter. For several days now, it always takes time to crank in the morning (and only in the morning, no problem during the rest of the day) and it is annoying me. Is there possible air in the system? How do I properly bleed it to get the air out and make it one click again? Is it possible that the air got in my IP?

TIA.

It's possible there's still a bubble trapped somewhere, might also be possible that theres a tiny air leak at the filter you replaced letting air in overnight. I'd doublecheck the filter is indeed completely full, top it off if necessary, give it some primer pumps with the filter bolt still loose until no more air comes out, then a few more after you tighten it, crack the injector lines at the injectors and crank it until you see air free fuel come from them all, then see what happens.