Cranks but no start

[birddog777]

Hi. I have a 2010 jeep Liberty 3.7 that cranks but doesn't start. Sometimes it starts no problem. Then other times the starter will crank but it doesn't start. Like it's not getting gas. I took out the fuel pump a few times tried to replace with a used one from an auto Wreckers but it didn't work. Put the old one back in. Was good for a few weeks then started acting up again. Sometimes have to let it sit 20-30 minutes before it will turn over. Do you think it could be the fuel pump or dirty injectors? It has an air lock problem too. And suggestions would be appreciated.
The only codes that come up are for the catalytic converter, and or 02 sensor for an incorrect fuel air mixture problem.

 

[Pitneykk]

I would start with those codes you are getting is the cat or the rest of the exhaust clogged?

 

[birddog777]

Just posting what the problem was. I did get a used fuel pump I got from a salvage place. And now it starts and runs no problem.