current ramping with a fuel control module?

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  • diesel71
    Senior Member
    • Feb 2008
    • 921

    current ramping with a fuel control module?

    I cant seem to get a good answer about current ramping a fuel pump that is controlled by a fuel pump control module? anyone have a good or bad movie /screen shot?. i see no reason why not, i know the control module will speed up or slow down the pump so the wave forum will rise and fall but we can still see the condition of the commutator and brushes.
    any thoughts or help ?
  • Crusty
    Senior Member
    • Dec 2007
    • 2450

    #2
    Sure. Why not-??
    An electric motor is an electric motor.

    Brushless may be an issue but even it will still need current flow.

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    • maven
      Senior Member
      • Mar 2014
      • 269

      #3
      Might be easier to get good results on pump condition/current draw just by hotwiring pump during your tests. youd probably need to know the frequency at which the FPCM operated, the duty cycle, etc...to begin to fully interpret readings with pump controlled by FPCM, unless you can command pump to 100% duty cylce.

      I would imagine that if all you wanted to do was verify commutator condition with the pattern it shouldnt matter at all though. You just couldnt do much with the actual amperage readings without all the information.

      Though if you did know the PWM frequency (GM likes to use 25kHz currently) you could use the scope to check the output from the FPCM is the proper frequency and matches commanded duty cycle.....That could come in handy. Some future random lean code for no reason, scope the FPCM and find out its switching at 5kHz instead of 25kHz and its causing surging in the pump....something weird. Oh ****....thats happening to me next week now.
      Last edited by maven; 02-04-2015, 01:19 PM.

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      • greasybob
        Senior Member
        • May 2008
        • 1590

        #4
        try this http://productforum.autorepairdata.c...ead.php?t=5652

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        • Crusty
          Senior Member
          • Dec 2007
          • 2450

          #5
          Originally posted by greasybob
          That was your usual good work Bob.
          You used one of the tools in your arsenal and found an anomaly. Testing AFTER the repair confirmed the original diagnosis.

          The more times the equipment is hooked up or connected, the more "Known Good" conditions are gathered, which then means you will recognize something different or odd when the problem vehicle shows up.

          That's one of the reasons I keep harping about Shop Stream Connect. SSC.
          That makes it EASY to save and review collected data, even weeks, months or years later.

          Of course if the equipment is unstable or unpredictable, all our efforts at collecting data, whether it's in our heads or in our computer files, is for naught.

          That was the kind of good work I've come to expect from you Bob...Thanks.

          Comment

          • maven
            Senior Member
            • Mar 2014
            • 269

            #6
            Originally posted by greasybob
            Nice find. Did you know the frequency of the FPCM PWM or did you just guess to figure out time scale to find the glitch. Looks like Ford uses 10kHz on that, and you stated low side control. GM uses 25kHz, and high side control currently on the trucks. A good GM truck pump can draw 20-22amps!

            Comment

            • diesel71
              Senior Member
              • Feb 2008
              • 921

              #7
              thanks for the reply's. until I get a better reason not to do it, im going to current ramp a pump controlled by a module to check for brush and commutator wear.

              Comment

              • Crusty
                Senior Member
                • Dec 2007
                • 2450

                #8
                Originally posted by diesel71
                thanks for the reply's. until I get a better reason not to do it, im going to current ramp a pump controlled by a module to check for brush and commutator wear.
                Grab every chance you get to build your own "Known Good" current waveforms and values at various locations in the circuit.
                Remember, the current starts way back at the generator or the battery. It doesn't ALL come from the FPCM although it may be processed by the FPCM so current waveforms could conceivably LOOK different depending on exactly WHERE is the circuit you take your samples from.
                You're a sharp guy. I know you can make sense of it once you gather enough examples for yourself.

                Please keep us informed of what you find.
                Saving files and viewing them using SSC can be a benefit for everyone.

                Comment

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