05 jeep liberty wont start and just replaced the fuel pump do I have to prime the fuel pump or reset something?

To start with, code 12 is loss of battery voltage within last 100 engine starts, which is normal if you had the battery disconnected, code 55 just means the computer has completed testing. I'm sure your problem is fuel related. Why did you replace all that stuff?
Listen close when you turn the key on, you should hear the fuel pump run for a couple of seconds to prime the rail. If not, start at the fuel pump connector and check for power when someone turns on the key. If there is no power, work backward toward the battery. You should check with a dealer as Chrysler/Jeep had a recall on the relay /fuse box under the hood(power control module), which would fail causing problems such as you are describing. They are really expensive, and the company was sued due to the many failures. If yours is bad, and you get no factory help, try to find a salvage part. I have installed used ones before that worked OK, but there is no guarantee how long.

Most likely a fuel pressure regulator leaking, or failing fuel pump.

You could have a fuel delivery problem. Start by

• checking fuel pressure. Fuel injected cars are very fuel pressure sensitive. Fuel pressure is very important and must be within specifications. However, if the pressure is low, it does not mean the pump is bad.
• A plugged fuel filter, a pinched line, and low voltage at the pump can contribute to low fuel pressure. All three must be checked before replacing the pump.
• Rrefer this link http://www.carpartswarehouse.com/carmode... to learn about other parts of Jeep Liberty. Also you can get Jeep Liberty parts at good price.

needs to be primed

need a fuel system chec-the gas pump and the regulator-also the injector pulses may be failin--find an honest mech that can testum with instruments

fuel pump relay . you should hear the fuel pump run for 5 seconds as soon as you turn the key on .after that the cranking sensor takes over when engine it turned over to start

It sounds like a fuel issue. Possibly a bad fuel filter or fuel pump. I would start by replacing the filter as it is a much cheaper fix. I hope this helps.

bad fuelpump, good luck . just make sure you have spark if so ,then il bet fuelpump is bad, just replace it. it is located inside fuel tank.hope this helps.

This is Common. The Compressor will run even on Heat settings. It is simply Priming for actions that the Owner could Initiate. Not a big Problem.

Yes you have to check your pressure with a mechanical gauge first. If the pressure reading is good replace the oil pressure sending unit. They are known to go bad, and oil pumps going bad is rare.