1997 Chevrolet Truck Blazer 2WD 4.3L SFI 6cyl.
First of all check for spark at the end of the coil wire. You may use a test plug as not to shock yourself.
You can make a test plug with a new spark plug and some wire, a mini hose clamp and an alligator clip. First open the spark plug gap to around 0.075” and strip both ends of a 16 gauge wire about 4 foot in length. Attach the mini hose clamp around the threads of the spark plug cause that is a ground and secure it with the mini hose clamp with the bare wire end in between to make a good connection. Next, take the other end of wire and secure to an alligator clip.Now, you have a test plug. Remove any spark plug boot you want and insert your test plug onto the spark plug wire end you just pulled off and ground the alligator clip. Lay the spark plug in some shade somewhere under that hood and then crank the engine and look for spark. It should crackle with sound and should be blue but red is ok, orange is a little weak. If it can jump that 0.075” gap you should have no problem igniting an engine. You can also use that to check coils on some vehicles.
If you have no spark, then check to make sure you have voltage to the ignition coil's primary wire when the key is on run at the pink wire, refer to this wiring diagram, click here. If no voltage refer to this wiring diagram, click here and check the fuse ECM-1 Fuse 20A (hot in run) for voltage. You can also test the condition of the entire primary circuit to see if it is functioning by attaching a 12-volt test light to the tach wire (white wire on coil) and while cranking the engine the test light should flicker if the primary circuit is opening and closing like it is supposed to. Last, check the ignition coil as described, click here.