Try unplugging the mass airflow sensor - MAF sensors have the capacity to sometimes cause a no start condition. If it set a code for a MAF sensor, that's the direction I would look. I understand that your mechanic has been putting crank sensors on for a reason, but I would honestly be hesitant to put one on unless you have a trouble code for it. Remember, the computer knows what's going on in nearly every situation on a truck like yours. Chances are, if the crank sensor wasn't doing its job, or the crank senor was falsely reporting cranking RPM, the computer would know something is up and set a DTC most likely.

Thanks Prometheus. The battery doesn't seem to be the problem. The engine is turning over very good but it won't fire as if there is no spark. But the spark has been checked and there is 60+ lbs. of fuel pressure.

Did it again. No codes showing up. Turns over very good...just not firing. Changed the MAF (Mass Air Flow) sensor about 3 months ago and all seemed well...until today. Truck sat for 2 and 1/2 days.
Can smell fuel coming from exhaust.
This is very frustrating.
On the plus side....Now sitting at home unable to go to work.
HELP!!!

Okay, so you smell fuel ... do you have spark?

Took it to the GM dealership yesterday. They are telling me the cap and rotor are bad. They were both replaced about a year and a half ago. I don't doubt that they may need replacing since they were not Delco brand, but it doesn't make sense to me why the problem always shows up after sitting for several days....in a garage out of the elements. Picking up the vehicle this AM and will see what happens. I will post the results but it may take a while before I start popping the cork off the champagne bottle. Thanks Nullhead!!

Spark has never been an issue in the past...it always had spark...that's what is weird.

Natural condensation in the cap can cause corrosion and high resistance in the cap its self. I can see the cap causing these problems but what else can be an issue is the little spring in the cap/on the rotor. The spark travels down the center point and into the rotor, if that contact inside the cap that goes to the rotor isn't good, then you'll have exactly that problem.

Glad you got it fixed!