Chevrolet Repair: 1997 BLAZER, crank sensor, mechanical aptitude

Question
I HAVE A 1997 BLAZER IT DOESN'T ALWAYS WANT TO START I PUT A NEW COMPUTER CHIP IN IT CHANGED THE CRANK SENSOR. IT WAS FINE THE NEXT DAY IT WOULDN'T START AGAIN I CHANGED THE CO2 SENSORS AND I ALSO PUT A NEW FUEL PUMP IN ,AGAIN IT WAS FINE IT ONLY STARTS SOMETIMES THERE IS SOMETHING WRONG AND IT WONT COME UP ON COMPUTER DON'T WANT TO KEEP PUTTING MONEY IN IT CAN YOU HELP

Answer
Hi Fred,

Ignition Module can intermittenly mess up, but I am not saying to run out and get that.  

Since you put in all those new parts, I am going to assume you have mechanical aptitude.  So I will give you some things to try.  Hopefully, this will happen at home.  If so, check for fuel supply at the fuel rail.  Should be a valve to screw a fuel gauge onto.  If you have pressure of at least 40 psi, then check for spark.  You do this by hooking a timing light to a plug wire and turn the key.  The light should blink consistantly.  My guess is one of these systems is not working.  However if they are, then write back.  If it is spark, suspect a coil, or ignition module.  

You don't have a chip in your ignition key, do you?  If so, this could indicate a malfunctioning theft control device.

Good luck.  Stop changing parts until we narrow this down.

C J S