Originally posted by linky:
was wondering what would keep the pcm from firing the injectors.


I'm no expert, but my understanding is that the PCM figures out where the pistons are by looking at the crank sensor. So, for example, when the #1 piston approaches top dead center the PCM gets a pulse from the crank sensor. BUT, the PCM is smart enough that it knows that when #1 is at top dead center, it could be on the compression stroke, OR, it could be on the exhaust stoke. To figure out which stroke its on, it looks for a pulse from the CAM sensor. When the PCM gets a cam sensor pulse, the PCM can very quickly figure out which cylinder should be on the intake stroke, and fires that cylinder's injector. And since the PCM knows the firing order of the engine, it can then figure out which injector to fire next, and next, etc. (It doesn't need the cam sensor any more - just needs it to get started. If'n it doesn't get a cam sensor signal when starting the engine, it can't figure out which injector to fire.)

The PCM uses the crank sensor to keep track of engine rpm and where the pistons are so it knows when to fire which coil. (It doesn't need to know if the piston is on the compression stroke or exhaust stroke, since the Contour uses a 'waste spark' ignition system - it fires the sparkplug on both the compression stroke AND on the exhaust (waste spark) stroke.)

Pick up a 'spark testor' ($2) at your favorite auto parts store and check for a spark. If you don't get a spark, then I'd suspect the crank sensor (or its wiring) is not letting the PCM know where the pistons are. If you get a spark, I'd suspect the cam sensor (or its wiring) is not letting the PCM know where the valves are. (If you have a 2-channel oscilloscope, you could check for both the crank and cam sensor signals while someone cranks the engine.)