The Chevrolet Blazer (and its cousin, the GMC Jimmy) can refer to one of several SUV models produced by General Motors including the Chevrolet K5 Blazer, Chevrolet S-10 Blazer, Chevrolet TrailBlazer, Chevrolet Tahoe, and Chevrolet Blazer.
@cminks you need to let us know what year and what engine your Blazer is. You also want to let us know what you have checked. This could be an issue with the crankshaft position sensor as well as multiple other things.