1997 With No Spark

Need Help I'm New To This Thing. Have A '97 Blazer 4.3 L 4 Door That Has A No Spark Condition. Have Replaced Ign. Module And Cam Sensor Still No Luck, What Am I Missing?
Also am not getting any info. from diagnostic terminal with scan tool.

97 is a bad year for ign switches.
Check all ign switch feeds and all power feeds to fuse boxes and 12 volts on both sides of fuses.
Verrfy good coil.
And ign power to it.
Does the scanner power up?
Are you checking for spark at plug wires or out of coil?
Is the dist turning when cranking?

All feeds are powered, ck'd spark at coil and spark plugs. Tried different coil and crank sensor also. Distributor does turn when engine is cranked. The scan tool does power up but states that it will not communicate.
Had issue with ignition switch before when trany was acting up

Is the scanner picking up any other computers?
Will it read transmission data?
You May want to try another scanner.
You need to get communcation to see what is going on.
Have you checked all power and grounds to the VCM engine /transmission computer?

"Distributor does turn when engine is cranked" That is not good! I assume he means rotor ?

correct rotor turns not the distributor, also have used two different scanners still no luck.
is it possible ecm bad?

Yes.
But do a pin out check on your dfiagnostic connector.
http://www.troublecodes.net/OBD2/

And do a pin out voltage/ground check on the computer.

All fuses good?

Back to first post?
Have you checked the crank sensor?
Does fuel pump prime up key on or run engine cranking?

crank sensor changed, fuel pump does not cycle.
While driving down the road my wife said that truck lunged like as if engine shut off for a second then took off again all at 70 mph

changed ignition switch last night, still no spark. Applied 12v to fuel pump feed under hood and pump runs.
Did pin ck out on data port and it ck'd ok. (power and grounds). I have read that the vcm recieves refrence pulses from the dist. Do I have a bad vcm? or possibly bad oil pressure switch. Will the switch have any thing to do with pump psi and ignition spark?

No on oil pressure switch.
No on dist reference pulse.
The crank sensor handles engine cranking and running pulse to VCM.

Could be bad VCM but go threw all test first.
The all data sub or a factory repair manual has all test.
http://www.alldata.com/products/diy/index.html


Make sure crank sensor is pulsing a signal to VCM.
Double check wiring and plugin on crank sensor.

I would also do a voltage and ground pin out on VCM.
Work on getting scanner communication.
It will show a lot of problems if you can get it to communicate.
Does the scanner show/read any transmission or abs or body or engine computer data?

shows no data at all, says that there is no comunication.