96 S10 2wd 4.3L starting problems

I have a 96 S10 2wd 4.3L auto that has starting problems. The problem is when you turn the key to crank the truck the motor is turning over and sometimes it cranks immediately then sometimes it may take 2,3,4,5,6,7,8 seconds to crank or not crank at all, but when you turn the key back then try to crank again it starts immediately. Battery has been load tested. The alternator has been tested and the starter and solenoid have been tested. any help would be appreciated?

If the starter is turning it over good run a fuel pressure test and post back pressure readings.
How is the tune up end?
Ever been tuned up?
How many miles on it and tune up?
Any check engine lights on?

sounds like fuel pump. try this turn key on until you hear pump and then turn it off do this about 4 times then try starting it. i do this to mine i no i need to replace my fuel pump.