2003 Jeep Laredo Starting problem

My Jeep Grand Cherokee takes two or three cranks to start-up. It normally starts right up on the first start of the day. But for subsequent starts, the engine turns over but no start on the first try. Then after 2 or three starts it cranks up and runs fine thereafter. Plenty of starting power available to turn the engine over. I downloaded 2 engine alert codes; crankshaft position sensor and emissions sensor bank 1. I replaced the crankshaft position sensor twice. I tried using fuel additive and better octane. When I have someone turn on the ignition, I can hear the electric pump come on.