I have a rough running '99 Jeep Cherokee Sport. In order to start it I have to pump the gas. Once it warms up it idles high, but runs fine. I have read some other stuff and I was wondering if it could be the crank shaft positioning sensor?

 

Could be the fuel pressure check valve(I believe that's what the one way valve is called) failed

 

I had a similar issue with mine and couldn't figure it out and had to take it to a mechanic ( I hate doing that ) he told me it was the battery . I didn't think he was correct as it was winding over ok just wouldn't start or idle properly. I did eventually change the battery and it fixed it. Haven't had a single problem with it for over a year. Go figure.