Chevrolet Repair: 2001 chevy blazer no start, chevy blazer, crank sensor

Question
Hey Todd-here's the issue.  2001 chevy blazer 4.3l v-6, truck towed inti our shop monday no start.  Did module-no go.  did coil-fired, started.  I drove for a couple days no issues(also did cap and rotor)returned to cust. yesterday.  Last night 9:00 pm cust. called, blazer quit.  I towed back into shop ck'd spark on the side of road had little or int. spark.  Question-does crankshaft position senson come to mind.  I never had an issue with one but...my  ACDelco jobber says they sell a ton of em.  Could this possibly be my issue or do you have another thought?  I've had good luck   on your site before so here I go again.  Thaank you in advance for your thoughts.  BTW I own a dealership(sole proprtor)have nearly 30 of these in stock, had thousands of em but at this moment, this has me stumped but anyway...if this was easy-everybody would be doing it, huh? Thanks again

Answer
if youre still getting a spark, even a little, i wouldnt think its a crank position sensor. if thats malfunctioning, you would have zero spark. make sure you have everything else, air, fuel. if both are ok, then go after spark, and the first thing i would check is the ignition coil and go from there. if everything tests well, you might want to consider a defective module. now, one thing, im not saying a crank sensor is out of the question. just not likely. if everything checks out, you might want to try a realearn on that, or try that first. then if everything checks out, you might want to consider that. this is a tough one.