There are a number of things that could cause a Jeep Liberty to fail to start, though with modern cars the most common reason is a dead battery. However, if your SUV has not been well taken care of with regular maintenance, then there are more complex problems that may be responsible. Generally, in a well maintained vehicle the problem will be in the electrical system; however, in a neglected one, there will most likely be mechanical problems preventing it from starting.
Sit in the Jeep and turn the key to the "On" position to crank the engine. If none of the dashboard lights comes on, the engine doesn't turn over and the the headlights don't come on, then there is a problem with the electrical system, most likely the battery.
Take the keys out of the ignition and pop the hood of your Jeep to inspect the battery. If there is foam on the battery, then you need to call a tow truck. The battery is leaking acid, and you need a professional car mechanic to fix it because of the potential for acid burns. However, if there is no foam, then you can thump the battery posts with your shoe or a rubber mallet to reconnect the posts. Try to turn on the SUV; if the lights come on, then the problem is not in the electrical system. If the engine turns over but does not start, then you may have a dead battery and need a new one. The battery can be removed by unscrewing the battery posts and retaining clamps by hand, though a flat head screwdriver can be used for leverage. Slide the battery out by pulling on its built-in handle then sliding the new battery into place. Reconnect the retaining clasp and post clamps by hand, then try turning the car on again.
Turn the car off if the Jeep Liberty won't start after installing a new battery but the electrical system is functional. You may have a flooded engine, which means that the spark plugs are wet and cannot generate a spark. To dry the plugs, you need to enable the Clear Flood mode by depressing the accelerator all the way to the floor first then continually turning the ignition on and off. This will cause the motor to pump air instead of fuel through the cylinders and will dry off the spark plugs. After a few minutes, take your foot off the accelerator and the key out of the ignition. If your Jeep Liberty does not start after this, you have a mechanical problem and will need to use custom diagnostic equipment to properly troubleshoot the issue.
