I've got a stumper. . .On a really cold day my wife tried to start the 2000 Blazer S10 4x4 4.3 vortec. The battery died down after trying to turn over for several minutes. I hooked it up to the charger, tried to turn it over and it makes a bad crunching noise from the starter. Push it into the garage and find out the nose of the starter is split in two. Take it in and find out that it isn't the starter for this year, was a rebuilt anyway, I opt for the extra 15 bucks and get the new smaller - high torque starter. So after I decide to put in a 2nd used fuel pump (seems to be working, makes noise on key turn), cap, rotors, plugs, wires, crankshaft position sensor. Tested the ignition module, its good. It seems to crank over very hard, the engine seems to make the starter roll back every once in a while, and it doesn't fire at all anymore. please help.

 

Sounds like that high torque starter you sprung for isn't up to snuff. The roll back would be from the compression in whatever cylinder(s) on the compression stroke pushing back.

 

Mileage?

Sounds like the distributor gear is broken/worn causing a timing issue.