Electrical problem
1999 Chevy Suburban V8 Four Wheel Drive Automatic too mu miles

My suburban will not start. will turn over but cuts out 2-3 seconds later. will start in pm however. security light on dash stays on when it will not start. fuel pump is working. doesn't happen all the time.

Sounds like your having an issue with the security system. It could anything from the chiped key to the ignition switch or the security system module. You will probably need to take it to a qualified shop for this one as this can be very difficult to diagnos and there is very little in aftermarket manuals to lead you in the direction needed. I hope this helps and thanks