I have a 1998 Ford F150 4x4 with a starting problem?

It seems to have a ground problem or it may be something else. It cranks slow off the start but then get to normal cranking but takes a while to start. I have replaced the battery, battery cables, cleaned the ground spots so I have a good connection. I also replaced the fuel filter and in tank fuel pump but still have this issue. Any ideas will be appreciated.

Added (1). I have replaced the starter and that wasn't the problem. The next thing I will try is replacing all the engine to body and frame grounds.

No way

If it's cranking slow… Even if only to begin with, this would point to the starter motor.
You have replaced the Battery… And just about done everything else! I would put my money on the starter.

If shorting the solenoid with a screwdriver produces the same slow crank, starter is broke,

@Wayne K: You've contradicted yourself: In your question, you stated:

" It seems to have a ground problem. "

and followed by: " I have replaced the battery, battery cables, cleaned the ground spots so I have a good connection."

and now the update: " Update: I have replaced the starter and that wasn't the problem. The next thing I will try is replacing all the engine to body and frame grounds. "

and " starter was replaced still doing the same. Suspect engine to body or frame ground."

Do you really know how many grounds you've missed in the beginning? For the truck's starting system? Go to your local library and get a copy of the Ground distribution diagram for your truck. You've thrown everybody off in the beginning.

What happen if all grounds clean by you this time and the problem remain the same? : Hard to start?

Back to square one and recheck the basics. The problem could cause by some other things. (Hint: " but takes a while to start. "

Chassing your tail huh? Have fun and good day.