Is it a liberty or a Grand cherokee. And whats the actual problem your having? If its a gc my wifes don't stay on very long at all. We also just had 2 replaced and before that the check engine light would come on and the glow plug light came back on after it started some times.
mine hardly come on, but I did replace my battery and that made a huge difference in how fast it spun the motor over, spinning faster made it start a LOT faster. even tho its a red top, does not mean it will live forever, replace that factory battery before ya get stranded.