You should never replace parts unless you are sure that part has failed. You began your diagnosis correctly, but you didn't finish.
First, is there a check engine light on? If the crank sensor was bad, there would certainly be a check engine light.
The procedure for diagnosing a no-start (when engine cranks) is:
Spark at plug
Fuel (including pressure, injectors firing)
All related sensors/wiring and computer (although this can be checked first with a scanner, before spark at plug)
You're computer needs to see both a crank speed reading and cam position reading for it to tell the coils to fire a spark to the plug. Because you have spark, I believe your sensors are fine. Also, your computer is good, otherwise you wouldn't have spark.
Since you've checked spark and fuel pressure, use an automotive stethoscope to listen for your injectors firing. You'll hear a distinct clicking sound. If your injectors are firing, the valve timing may be off (bad timing chain). You can verify this by doing a compression test.
If your timing chain has slipped, just replacing the timing chain wouldn't be economically sound, as that would be like putting a band aid on a gunshot wound. The rest of the motor will be just as worn as the timing chain. However, I do not recommend rebuilding this motor unless you want to keep this truck for 10 more years. There are too many low-mile used engines for dirt cheap.
Tuesday, February 1st, 2011 AT 11:59 AM