So I assume you mean the starter is cranking the engine. If that's right and it won't run, there are three circuits to check; spark, fuel supply, and the trigger circuit that turns both of them on. The fastest place to start is by listening for the hum of the fuel pump. You should hear that for just one second after turning on the ignition switch. If necessary, listen by the tank while a helper turns the switch on and off. If you don't hear it running, try banging on the bottom of the tank while your helper cranks the engine. If the engine starts, the pump is beginning to fail. It will continue to run until you stop the engine, and it might not cause a problem again for days or weeks.
If the pump runs for that one-second burst each time you turn the ignition switch to "run", check for spark next. If it is missing, grab an inexpensive digital voltmeter or a test light and check for voltage on the dark green / orange wire at the ignition coil, any injector, or either small terminal on the back of the alternator. You should see 12 volts there for one second after your helper turns the ignition switch to "run". What is important is that voltage must come back and be steady during engine cranking. If it does not, suspect the crankshaft position sensor or the camshaft position sensor.
Sunday, March 6th, 2011 AT 6:18 PM