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Thread: Fuel Pump Diagnostics

  1. #1

    Default Fuel Pump Diagnostics

    I'm working on a '02 Chevrolet Blazer and using manual #24071 for S-10 pickups.

    I have a no-start condition and the fuel pump is not running (no whirring noise when ignition switched to "ON").

    Referring to Chapter 4, page 4-4, Fuel pump electrical circuit check:
    The relay is clicking when the ignition is switched "ON"...can I safely say the relay is functioning properly?

    And if after completing step 14, there is voltage at the fuel pump, is the corrective action to replace the fuel pump? The manual doesn't say.

    Also, my version of the manual doesn't cover wiring diagrams for the CSEFI fuel injection system. Do I refer to the CMFI wiring diagram on page 12-26? Are the CSEFI and CMFI diagrams the same or was this an omission from the manual?

  2. #2
    Join Date
    Jan 2007


    Just because a relay clicks doesn't mean that it is passing voltage through the controlled circuit. BUT - since you are getting voltage to the fuel pump, you confirmed that the relay is working. Make sure the fuel pump ground circuit is good. If so, the pump is bad.

    Contact one of our tech services reps at 1-800-442-4637 or email them at research@haynes.com. Be ready to give them the number-letter combination on the first page of your manual, just to the right of the Haynes logo. They'll do what they can to help.

  3. #3


    I verified the source of my problem was a bad fuel pump.

    For anyone else working on the S-10 line of trucks, I wanted to point out that step 14 of "Fuel pump electrical circuit diagnosis" on page 4-4 requires an assistant to operate the ignition while you check for voltage at the pump connector. The PCM only supplies voltage for 2-3 seconds. This is noted on page 4-3, but I overlooked it and was stumped for awhile as to why I was not receiving voltage at the pump connection.

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