96 blazer

ok i think i found my problem.. 96 blazer will not start when cold... but runs fine after warmed up good. when i turn it over while cold it will not start and the tach is going crazy up and down... well i was informed most likley the crank sensor because it controls tach and tach shouldnt go up and down that much when trying to start. fuel pump and presure regulator has been ruled out.

havent been able to get under truck yet but does the harmonic balancer have to come off to change this blazers crank sensor?
god i hope not!

have you had the trouble codes scanned?

Don't just start throwing random parts at it.