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Pulling injector wires while engine running.

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    #1

    Pulling injector wires while engine running.

    Will testing injectors one by one to see if they are all firing by pulling the plug and pushing back on while the engine is running ruin anything? Will my L-jetronic computer not like this?
    I'm diagnosing an engine miss, and i feel its either:
    head gasket blow by between two cylinders, or an injector.

    Cheers
    ///Monstrosity. (OO≡≡[][]≡≡OO)

    Aside from showing yourself to be offensive, lacking experience and ignorant in the ways of business, you're also illiterate and imprudent. Beyond that, your sense of liability is severely impaired.

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    #2
    A compression test will tell if the head gasket has failed between cylinders. Other than ID'ing the cylinder(s) with the miss, I don't think you'll learn much from pulling injector connectors. If you pull the connector for the injector on a cylinder with a misfire, there won't be any change. Since the cylinder was missing before you pulled the connector that tells you nothing about whether the injector is firing or not.

    Pulling the entire fuel rail and cranking over the engine with the injectors pointed into a towel will tell if one isn't opening.
    The car makes it possible, but the driver makes it happen.
    Jim Levie, Huntsville, AL

    Comment

      #3
      Originally posted by jlevie View Post
      If you pull the connector for the injector on a cylinder with a misfire, there won't be any change. Since the cylinder was missing before you pulled the connector that tells you nothing about whether the injector is firing or not.
      Thats the test, if I pull say, No. 2 injector wire and the car starts running on one less cylinder (misses really badly) then put the plug back in and pull, say No. 3 injector plug and nothing happens (ie. no change in engine behavior), that would be to my understanding that No.3 injector has a problem.

      Yeah I'll run a leak down test, pressure test aswell to determine if it is the valve seats or rings.

      Cheers.
      ///Monstrosity. (OO≡≡[][]≡≡OO)

      Aside from showing yourself to be offensive, lacking experience and ignorant in the ways of business, you're also illiterate and imprudent. Beyond that, your sense of liability is severely impaired.

      Comment

        #4
        Well... If the ignition wire or plug for, say #2 cylinder, is bad and you pull the injector connector for that cylinder and the miss is worse, that doesn't mean that the injector is bad.

        I guess that what I'm saying is that pulling the injector connector (or the ignition wire) is only useful for identifying what cylinder is missing. It doesn't tell you anything about the cause of the misfire. Now if you swap the injector or plug to a different cylinder and the misfire follows the plug/injector, you have a probable cause.
        The car makes it possible, but the driver makes it happen.
        Jim Levie, Huntsville, AL

        Comment

          #5
          Have you checked to see if it's your spark going to the plugs or maybe the wires itself? When you say a misfire, do you mean like missing spark on a cylinder or what exactly is it doing?

          How do I spell stress relief?:hitler:
          :!:Open Track Days!!!:!:

          Comment

            #6
            Originally posted by elsabor67 View Post
            Have you checked to see if it's your spark going to the plugs or maybe the wires itself? When you say a misfire, do you mean like missing spark on a cylinder or what exactly is it doing?
            At idle it sounds like a noticeable "miss" every so many revolutions hot and cold...
            Also, under very heavy acceleration it "misses" the same as if it were at idle, except faster.
            Rotor, cap, spark plug leads and spark plugs were replaced a couple of weeks ago thinking that ignition was the problem.
            I'll change the coil anyway so that will be ignition all out of the way.

            I still think its fuel related.

            Actually, on the vacuum side of my FPR (where the vacuum line goes in) there was fuel inside that inlet!
            Now, I'm not sure just how the FPR works, but i would think that it would be faulty, or my ICV is rooted? Any ideas? My car is running rich as a bitch...
            ///Monstrosity. (OO≡≡[][]≡≡OO)

            Aside from showing yourself to be offensive, lacking experience and ignorant in the ways of business, you're also illiterate and imprudent. Beyond that, your sense of liability is severely impaired.

            Comment

              #7
              Finding fuel in the FPR vacuum line means that the diaphragm in FPR is bad. That in turn means that the fuel pressure isn't being correctly regulated. Replace the FPR and see if that doesn't help some.
              The car makes it possible, but the driver makes it happen.
              Jim Levie, Huntsville, AL

              Comment

                #8
                Originally posted by jlevie View Post
                Finding fuel in the FPR vacuum line means that the diaphragm in FPR is bad. That in turn means that the fuel pressure isn't being correctly regulated. Replace the FPR and see if that doesn't help some.
                Ah! Yes, I thought there would be a rubber diaphragm in there, would this in turn make my bimmer want to run rich?
                I live in Aussie, and a FPR retail AU$240 after trade discount...
                Just want to be sure I need this part before i go waste money.
                Cheers.
                ///Monstrosity. (OO≡≡[][]≡≡OO)

                Aside from showing yourself to be offensive, lacking experience and ignorant in the ways of business, you're also illiterate and imprudent. Beyond that, your sense of liability is severely impaired.

                Comment

                  #9
                  There's a test procedure in the Bentley manual that will tell if the FPR is operating correctly. I'm pretty sure that yours will fail the test, but you could run the test for peace of mind before purchasing a new FPR.
                  The car makes it possible, but the driver makes it happen.
                  Jim Levie, Huntsville, AL

                  Comment

                    #10
                    If theres fuel on the vacuum side of the FPR, its faulty. No test required.

                    Comment

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