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Manifold Pressure Sensor. Is it toast? 1800

Read info from Phil Singher's D-Jet overview, and applied "mouth" vacuum to the manifold pressure sensor, and basically there was none. I could blow air in both directions. Does this mean the sensor is toast?

Is this sensor also referred to as a fuel pressure sensor? (not the regulator, attached to the fuel rail).

Thanks for any enlightenment








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    Manifold Pressure Sensor. Is it toast? 1800

    I'll take a lot of grief for this, but I've rebuilt a couple of Pressure Sensors.From all I know, what Cameron has said about these thinks being carefully factory calibrated is true, But jeez, these cars are eons old and there's a lot that's out of calibration.

    To repair, carefully disassemble the thing (early ones have 4 screws, later ones have rivets.) Take care to note the position of the bellows (copper colored thing), although I don't think it really matters. Then turn your attention to the front (smaller) section and remove the diaphragm retaining ring. First one I repaired (20 years ago) I used a Saran Wrap doughnut glued to the diaphragm's external face with Pliobond adhesive. It worked fine. Latter redid it with 35mm shutter curtain material (I was studying camera repair at the time).

    I recently purchased one, as a spare, on eBay. Of course, when I got it, it would not maintain vacuum.So I dug out the old shutter curtain material and bought some new Pliobond at the hardware store and fixed it similarly. During a subsequent session of troubleshooting by swapping out components, I had occasion to use it for several days. No discernible difference between that one and my good one. So go ahead, find some thin, flexible material and some spray adhesive and have at it. You have nothing to loose and you may just be pleasantly surprised.








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    Oops - missed this point 1800

    The Manifold Absolute Pressure sensor, or MAP sensor, isn't the same as a fuel pressure sensor. The MAP's job is to compare the difference between manifold pressure (usually called "vacuum") and atmospheric pressure. ("vacuum" is still pressure, because it's greater than zero, but it's called vacuum because it's lower than atmospheric pressure which is something like 14.7 psi at sea level). The thing that's really cool about the MAP is that it accomodates changes in atmospheric pressure (like elevation changes), and makes adjustments to the fuel supply based on "vacuum," engine speed and engine load. Really very trick.

    It doesn't do anything as far as sensing or monitoring fuel pressure.

    Best,

    Cameron
    Rose City








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    Manifold Pressure Sensor. Is it toast? 1800

    You're correct: the sensor is toast.

    Sorry.

    Best,

    Cameron
    Rose City








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      Manifold Pressure Sensor. Is it toast? 1800

      Guys;

      Just one moment! You dont send the car to the crusher when the engine is shot, do you?

      The DIAPHRAM within is indeed toast (typically from fatigue), but not necessarily the whole sensor. Replacement kits were available.

      Cheers








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        Manifold Pressure Sensor. Is it toast? 1800

        No, Ron, I don't send cars to the crusher when the engine is shot. That's why I own 16 Volvos and have 8 or 9 more engines in the garage.

        All I said was that the sensor is toast. Because it is.

        I wasn't aware of any diaphram replacement kits being available - if you could share with us the source, I'm sure that a lot of brickboarders would be delighted to make use of it (myself included)!

        Regards,

        Cameron
        Rose City








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          Manifold Pressure Sensor. Is it toast? 1800

          I would LOVE to rebuild this.

          Also, the car is not starting currently, could this be the cause? Seems unlikely, not getting any spark.








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            Manifold Pressure Sensor. Is it toast? 1800

            If the damage to the diaphram is substantial enough, it could prevent the car from starting/running. Sometimes they have just a slight tear and the engine will still be able to run, though not quite correctly.

            I have no idea where you might be able to find a kit to rebuild it, but it's a Bosch part that was also used on other Djet fitted cars... Audi, VW, Porsche, Mercedes... check with whoever you can find that sells parts for those, I suppose.

            The other option would be to try to find a good used one - if you do this, you'll want to be sure that the part number matches what you currently have.

            The diaphram is brass (I think.. it might be copper but I'm thinking it's brass); its job is to move based on how much vacuum exists within the intake manifold. This has a significant effect on the fuel supplied via the injectors. Unlike some of the other components in the Djet system, the engine just won't run without the MAP sensor and there isn't a generic replacement or workaround that will fit the bill.

            This is a very sensitive item that's very carefully calibrated at the factory before it's sealed up. There's a 'well known' adjustment screw and another 'not as well known' adjustment nut (or screw... hmmm... been a while) inside. The exact placement of the diaphram is really important to get just right, or the input the MAP provides to the ecu will be incorrect, which will result in the incorrect amount of fuel being supplied to the engine.

            I'm certainly not saying to not try rebuilding it - just that it's not something as simple as rebuilding a starter or an alternator or.. whatever.

            Hope that whatever you do for a solution that it works out well.

            Best,

            Cameron
            Rose City







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