Holy Chrysler!

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  • Trindaddy
    Senior Member
    • Jan 2010
    • 339

    Holy Chrysler!

    Ok, so I think we've got the LDP testing down but i wanted to catch the opinion of you guys. Here's what we have done:

    Energize the PCM power relay (using the Modis), ground center wire at LDP, Apply vacuum to LDP port, using the EELD, pressurize system, and at this point can shut off car or remove ground at LDP wire and watch for pressure loss. Whatya think guys? Does anyone know why it is so that you can at this point turn off key and de-energize solenoid? It seems that we loose vacuum at LDP when we do this yet vent stays closed. Anyone know why?

    Neil
  • Joe Rappa
    Snap-on DSD
    • Aug 2007
    • 2050

    #2
    On an LDP System you close the vent valve by lifting the diaphragm. You need vacuum to close it, which you provided, but once the system is pressurized, the pressure keeps the diaphragm up by pushing on the bottom of it. As long as the diaphragm is up (lifted by vacuum, or held by pressure) the vent stays closed.
    Attached Files
    "You don't build a reputation on what you're going to do"
    Henry Ford

    Comment

    • Joe Rappa
      Snap-on DSD
      • Aug 2007
      • 2050

      #3
      So you know, there is an easier way to close the vent valve on LDP Systems.

      If you connect the smoke machine and turn it on (full flow) and command the EVAP Monitor to run, it will lift the diaphragm for you, and the pressure from the smoke machine will hold it closed. As soon as you see the flow drop off, or pressure build in the sytem, shut the engine off and finish your leak test.

      On some models it's even easier. Some cars pulse the LDP once on startup. All you have to do is connect the smoke machine, set it to full flow (either Test or Smoke) and start the engine. If it pulses the pump you will see pressure build in the system immediately. Shut the engine off and finish your testing.

      Giving credit where credit is due....I learned this from Glenn.
      He's pretty smart, but still, I've never really liked him.

      Have fun,
      Joe
      "You don't build a reputation on what you're going to do"
      Henry Ford

      Comment

      • Trindaddy
        Senior Member
        • Jan 2010
        • 339

        #4
        Ooooh thats slick! What till I tell Lyle (my partner). He (we) just worked on the one i'm referring to. Maybe some day he'll come on this site too. Until then I'll wow em with my knowledge! Thanks Joe.

        Comment

        • Glenn Richardson
          Junior Member
          • Feb 2011
          • 8

          #5
          Sure I'm gone for a few days and look at what you did -- POW right in the back!!! -- You don't have to like me BUT you will have to put up with me --ha ha ha

          Originally posted by Joe Rappa
          So you know, there is an easier way to close the vent valve on LDP Systems.

          If you connect the smoke machine and turn it on (full flow) and command the EVAP Monitor to run, it will lift the diaphragm for you, and the pressure from the smoke machine will hold it closed. As soon as you see the flow drop off, or pressure build in the sytem, shut the engine off and finish your leak test.

          On some models it's even easier. Some cars pulse the LDP once on startup. All you have to do is connect the smoke machine, set it to full flow (either Test or Smoke) and start the engine. If it pulses the pump you will see pressure build in the system immediately. Shut the engine off and finish your testing.

          Giving credit where credit is due....I learned this from Glenn.
          He's pretty smart, but still, I've never really liked him.

          Have fun,
          Joe

          Comment

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