No compression in #4 Cylinder
 

The car was running fine, then it just died. It would not restart, so i had to get it towed. Just to get it running again they had to replace the distributor cap. After that diagnostics were run and found out that i have no compression in the #4 cylinder. What are the causes of this?

Could be a burnt/bent valve, bad piston and/or rings, or a blown head gasket. Any of which requires the removal of the head.

So you (they) did a compression test and found #4 has no compression ? Or it is just not firing on that cylinder ? Because you said it was running fine before,,,,, Hummmm, All they did was a distributor cap replacement. How are the plug wires, Maybe the #4 plug wire is bad? Sparkplug ? How many miles are on your Blazer and what year is it ?T.J.