1988 Jeep Cherokee hard to start when its been sitting a co

Engine Performance problem
1988 Jeep Cherokee 6 cyl Two Wheel Drive Automatic

i have trouble in the morning.I have to crank the engine for about 15 seconds while pumping the gas rapidly.I know I shouldnt have to push the gas because it is fuel injected but if I dont then I have to crank the engine longer.I think the fuel loses pressure. When I drive then stop somewhere for a while it doesnt do it, only after an hour or longer. Ive already changed the fuel filter, fuel regulator. Spark plugs, distributor cap and rotor, ignition coil and the piece that goes under(electrical part), crankshaft position sensor, fuel injecters. Could my fuelpump be going out?Someone told me it could be the seals to the fuel pump could be corroded.