99 Blazer Fuse Box Diagram

Blazer Fuse Box

In the fuse box all fuses are named so you can replace the faulty fuse as per your problem.

If you have fuel pump problem then 

This will help.check the ecm B fuse beside fuel pump relay. That powers the fuel pump circuit. There must be a fuse and 12v present.

Pull fuel pump relay out, look closely at bottom of relay. Pins will be numbered. 

Check the corresponding socket to pin 30, for 12v. You can verify this is correct by pulling ecm B fuse, should lose 12v. 

Now check socket for pin 85. Is there continuity to ground? This is the ground pin for relay coil. There must be ground. (If no continuity to ground, you must access the bottom of fuse panel, locate the wire that goes to terminal 85, cut,extend, and connect to a good ground)

Pin 86 should have 12v when the key is on.This is the pin that energizes the coil in relay. (No power at pin86? You need to access the underside of the fuse panel, locate the wire going to that pin 86, and cut it so you have lots of length to work with. Now locate the wire, powering the unused fuse socket you found first. Cut, and join to the wire from the relay.)

The last socket for pin 87 is the load wire, it goes to the fuel pump.

Try pulling the DRL relay to see if the headlights go out. If they do, then I would suspect, you have constant power to the ign side of the fuse panel.

Thanks.