explorer won't start

Before replacing any parts you might want to see if you have a fuel or ignition problem. You can make a few checks to narrow it down. First check for spark as you have planned. As far as making the test the only way I know ( without a tester) is to use a screw driver placed into the end of the the plug wiring. Make sure you are holding the handle of the screw driver if you don't want to get a shock. If no spark then you will have to trouble shoot the ignition system. You can check to see if the fuel pump is running with help from an assistant. Have the assistant listen next to the fuel tank, while you turn the ignition key to the on postion. If the pump is running you should hear it humming. This dosen't mean the pump is mechanical good just the electrical part. (fuse relay, wiring etc). IF you have a fuel pressure tester you can test for proper fuel pressure which will verify that the pump is either good or bad.