I have a 2002 jeep grand cherokee v6 engine 4.0 liter. I have recently just replaced the battery and alternator. But when I try to start it, I have to pump gas and turn key simultaneously for it to come on. And when it comes on it stalls after a couple minutes. I thought it was the ignition or plugs in the ignition or maybe the fuel pump. What do your think is the issue?