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How do i build a diesel injection pulse meter or adaptor ?

  1. Sep 14, 2004 #1
    Can anyone help me attempt such a project?

    I basically need to be able to sense the injection pulse in the injector pipe (1/4 inch / 6mm dia.) and convert it to an electrical pulse so that a normal ignition timing light (strobe light) can read the input as it would on a petrol/spark ignition engine.

    thanx for your time.
    Last edited: Sep 14, 2004
  2. jcsd
  3. Sep 14, 2004 #2
    Make a 100 turn loop of #26 magnet wire that is large enough in diameter to put around the injector solenoid (loose loop). Wrap tape around to hold the loops together.

    Drive the base-emitter on a 2N3055 transistor with the loop outputs. Connect your strobe trigger connection across the collector-emitter on the transistor.

    You might want to add a 1k, 1/4 watt potentiometer in series on the transistor base and start with it at 1k, adjusting down until it's just enough to trigger the transistor.

    The 2N3055 is pretty cheap and it has pretty high gain. This means it will use very little induction current from the injector to trigger it.

  4. Sep 14, 2004 #3


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    Can't you just sense the signal controlling the injector solenoid in the first place?

    - Warren
  5. Sep 14, 2004 #4


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    Karl - is this mechanical or electronic injection? For electrical, see above.

    For mechanical, that should be in the service manual for the engine and calibrated to the pump drive. Well, with my limited exposure anyways... Otherwise you'd need to monitor the pressure (tough) or attach a vibration sensor to detect the opening when the pressure has exceeded the required pressure and then the closing when the pressure has fallen, not so easy as well. For a given RPM you could design a circuit that could compensate for only being able to monitor the closing, but eliminating the vibration from combustion might be very hard. Just thinking out loud...and a seasoned diesel tech would probably have a lot more suggestions.

  6. Sep 16, 2004 #5
    This is to sense mechanical fuel injection.'Snap-On' tools has this type of adaptor on the market,i was just trying to figure how it works.
  7. May 17, 2005 #6
    The sensor is around over the #1 cylinder high pressure injection line. Does anyone know how to find this pulse?
  8. May 17, 2005 #7


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    I did a search on Snap-On and one of the testers was required to be used with their pressure sensor. What unit are you looking at?
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