1996 Other Chevrolet Models Cold (Long time) Starts

Engine Mechanical problem
1996 Other Chevrolet Models 6 cyl Two Wheel Drive Automatic 100.00 miles

I have a Chev. C1500 1996. When the truck sits for more than 3 or 4 hours. The truck takes a long time to start. The starter turns over, but nothing. I keep turning the key on and off several times and it eventually fires. I replaced the fuel filter, ran cfoam through the gas. Cleaned the throttle body with carb cleaner.
Once it starts it runs great. Even If I stop at a store and come out it starts right away.

any ideas