I'll try my best to help you on this one. It sounds very interesting. I've never heard of a radio causing a no start on a Blazer before.
Let's check all the basics first. Check all the fuses labeled IGN 0, IGN 1 IGN3 etc. Check all the fuses for that matter. Lets make sure nothing blew while you were hooking things up.
If they are all ok, we may be looking at a coincidence.
We will then need to check to see if you have the basics to make the engine run, Spark, Fuel And Air.
See if you have spark at the ignition coil while cranking the engine. If you do, check at the spark plugs next. If no spark is present at the plugs, but is at the coil, then your distributor cap and rotor should be replaced.
If you have plenty of spark, we will need to check for the correct fuel pressure. If you turn the key to the run position, listen for a hum noise from under the truck on the drivers side. That will be the fuel pump that you will be listening for. If you don't hear the pump run for 2 seconds and then stop, you may have a bad pump, or some other issue with getting power back to the pump.
Just to clarify something. Did you cut wires and harnesses to install an aftermarket radio, or did you just replace the old one with another factory unit?
Does the truck start and then stall after 2 seconds? Is the security lamp on or flashing?
If you have questions or need clarification, please don't hesitate to replay to this. If you find the problem, please make sure to click the "Accept" button so I may receive credit for assisting you this evening.
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