How to Check the Electric Fuel Pump on a 1998 Chevy Silverado

The electric fuel pump in a 1998 Chevrolet Silverado is controlled by the powertrain control module, or PCM. When the PCM needs to turn on the fuel pump, it energizes the fuel pump relay. The fuel pump relay’s circuitry opens and sends roughly 12 volts of power to the fuel pump. When the fuel pump fails, the engine will crank but not start. An automotive scan tool with bi-directional controls must be used to command the fuel pump on using the PCM in order to determine if the pump itself is faulty.

Materials:

Automotive scan tool

Instructions:

1. Turn the ignition to the “ON” position and open the hood. Locate the Silverado’s 16-pin diagnostic data port inside the vehicle. This port is situated underneath the lower leading edge of the dashboard, approximately 6-inches to the right of the steering column centerline.

2. Connect an automotive scan tool with bi-directional controls to the vehicle’s diagnostic data port. Power on the scan tool and navigate to the bi-directional controls menu. This is the menu where you can use the scan tool to communicate with the vehicle’s computer and command certain features on for testing purposes. Depending upon the exact brand and features of your scan tool, your menu structure may differ slightly.

3. Locate the relay control box underneath the hood. It is in the back-right corner of the engine compartment, to the right of the brake fluid reservoir. Remove the cover from the relay box and read the diagram on the underside of the cover.

4. Note the location of the fuel pump fuse and the fuel pump relay on the cover diagram. Locate the fuel pump fuse inside the relay control center. Remove it and check to make sure it’s not blown. If it is blown, replace it. Locate the fuel pump relay according to the diagram.

5. Hold the scan tool in one and place your index finger from your other hand on top of the fuel pump relay. Command the fuel pump “ON” using the scan tool. You should feel and hear the relay click as you command the pump “ON.” If you do not hear the relay click, switch it with a known good, identical relay from inside the relay control box. In order to test the fuel pump, the relay must be operational and supplying the fuel pump with power. This step rules out a bad fuel pump relay.

6. Sit in the driver’s seat and command the fuel pump “ON” and “OFF.” Listen carefully for the fuel pump to cycle while you are doing this. You should hear an electric “whirring” noise each time you command the fuel pump “ON.” If you do not hear the fuel pump energizing (and you’ve verified that the fuel pump relay is operating properly) then the fuel pump is faulty and must be replaced.

Tips:

You cannot properly test the fuel pump circuitry without a bi-directional automotive scan tool. These tools can be rented or purchased from most auto parts stores as well as a number of hardware and tool retailers.

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Filed in: Automotive

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