* Under the hood in the fuse box: This is the most common location. The fuse box is usually located near the battery. Look for a diagram on the inside of the fuse box lid to identify the relay. The relay might be labeled "FUEL PUMP" or something similar, or you might need to consult a wiring diagram for your specific Blazer's year and model.
* Under the dash: Less common, but possible. Check the fuse panels under the dash. Again, a diagram inside the panel cover will help.
* In the Power Distribution Center (PDC): Some later models (though less likely for a 1990) used a PDC instead of a traditional fuse box. The PDC is usually located under the hood.
To find it definitively:
1. Consult your owner's manual: This is the best place to start. The manual should have a diagram showing the location of all relays and fuses.
2. Use a wiring diagram: A wiring diagram specific to your 1990 Chevy Blazer 5.7L will clearly show the fuel pump relay location and its connections. You can find these online through various automotive parts websites or repair manuals (like Haynes or Chilton). Search for "1990 Chevy Blazer 5.7L wiring diagram"
3. Visual inspection: Carefully examine the fuse boxes and relay panels under the hood and under the dash. Look for a relay that's similar in size and shape to other relays in the area and might be labeled as a fuel pump relay.
Remember to disconnect the negative battery terminal before working with any electrical components to prevent accidental short circuits.
