CKP and CMP Sensors

Collapse
X
 
  • Time
  • Show
Clear All
new posts
  • Modis500
    Senior Member
    • Sep 2012
    • 358

    CKP and CMP Sensors

    Got some screenshots I need help with. First one is a 2008 Ford 3.0 OHV in a Ranger. Has the CMP sensor where the distributor used to be. Looking at the waveform, why does it have the little kick on the downside of the voltage line?

    Second set of screenshots are a '99 Jeep 4.0 CKP to CMP Correlation. Why does the Modis have a dirtier shot of the CKP sensor on the waveform at 200ms screenshot, but when you change the time to 20ms, it cleans up the waveform considerably? Component test meter tells us that during testing, frequency will change, but Min/Max will not. On one screenshot, it does change on Min/Max, but the other, it does not. I tried it with filter on and off, not much change. At idle, it's a clean waveform no matter the screen time, from 20ms on up to 500ms. I'm fighting a hard-start on this Jeep, and everything I've found this afternoon is pointing towards CKP sensor.
    Attached Files
    "If you aim for nothing, you'll hit it every time!"
    Zig Ziglar
  • Joe Rappa
    Snap-on DSD
    • Aug 2007
    • 2050

    #2
    I'd say the Ford CMP sensor is dying. Here is a bad VSS on a Taurus. Same distortion when it crosses the 0V line. Just a bit worse than yours though.

    As for the Dodge pattern, as you slow the scope down, the sample rate decreases. You can compensate by putting it in peak detect mode of you need to.
    Attached Files
    "You don't build a reputation on what you're going to do"
    Henry Ford

    Comment

    • greasybob
      Senior Member
      • May 2008
      • 1590

      #3
      Did you have a cam position sensor code or have the engine cutting out at around 3000 rpm ? Here is a good and bad 3.0 cam sensor waves. The bad is from a Taurus that would start to cut out at around 3000 rpm. Is the jeep a hard start all the time or just hot ?
      Attached Files

      Comment

      • Modis500
        Senior Member
        • Sep 2012
        • 358

        #4
        Joe and Bob,

        Thanks for the quick reply this morning. The jeep is an intermittent no start. Temp doesn't affect it at all. As for the Ford, it had a CMP code upon arrival. I did replace this sensor after testing, and have not seen that dip so it makes sense with the code. I just needed se old fellas like yourselves to confirm my find. As for the Jeep I'm going to start testing it this morning and try and get it to fail. None of the usual suspects with Jeep hard start are evident (faulty injectors, fuel pump, etc.) so we'll see where it goes. The CKP sensor just looks so trashy while its running, maybe I'll catch a break and find a failed sensor today. And one more thing Joe, I tried peak detect and it cleaned up somewhat, but not entirely.
        Thanks Again

        Tom
        Last edited by Modis500; 02-27-2014, 05:19 AM. Reason: Loss of train of thought
        "If you aim for nothing, you'll hit it every time!"
        Zig Ziglar

        Comment

        • greasybob
          Senior Member
          • May 2008
          • 1590

          #5
          Just curious if you replaced just the cam sensor or the whole synchronizer ?

          Comment

          • Modis500
            Senior Member
            • Sep 2012
            • 358

            #6
            Bob,

            On the Ford it was a problem child handed over to me. Tech threw a CMP sensor in it for the code without seeing waveform. 2 weeks later its back with same code. I scoped it and found this. So no, the synchronizer was not replaced. Found no slack in gear, just replaced faulty cheapo sensor.
            Tom
            "If you aim for nothing, you'll hit it every time!"
            Zig Ziglar

            Comment

            • Modis500
              Senior Member
              • Sep 2012
              • 358

              #7
              Got a scanner screenshot that I believe shows this CKP sensor dipping out while driving. Again, I'm looking for confirmation that I'm seeing this right, or that I might be mis-reading scan data. It's in the middle of the screenshot (CKP Count) where it does not peak out like the rest of the data on that PID.
              Attached Files
              "If you aim for nothing, you'll hit it every time!"
              Zig Ziglar

              Comment

              • Crusty
                Senior Member
                • Dec 2007
                • 2450

                #8
                My first question is...did the vehicle exhibit anything like a stumble or shake that you could tell.
                I looked up the description for the cam and crank sensors.
                your scope capture shows it fairly well.
                The flywheel has three sets of four notches. The cam sensor has one notch.
                the cam sensor scope signal should detect the beginning of the vane gap and then the ending of the vane gap.
                The crsnk sensor showing four signals at a time should stay consistently at the same location with each cycle of the cam sensor.

                This is whete having one machine the scanner and a separate machine for the scope can be beneficial.
                If you can reproduce the signal variation on the scanner and at the same time reproduce a drop out or another indication on the scope then its just a matter of confirming the CKP reference voltage and ground.

                Apparently there are cases of wiring problems from the firewall forward along the right side valve cover all the way up to the ignition coil located at the front of the right side valve cover.

                Confirm your scan data with scope signals. Sometimes tough to reproduce the issue but that is the best way unless you can roll 7's

                Comment

                • Crusty
                  Senior Member
                  • Dec 2007
                  • 2450

                  #9
                  Your earlier "dirtier" 200 ms capture may actually be displaying the CKP dropping out
                  Try saving your scope recordings to your computer and see what SSC shows.

                  Comment

                  • Modis500
                    Senior Member
                    • Sep 2012
                    • 358

                    #10
                    Crusty,

                    No driveability complaint, just intermittent hard start. I have saved numerous shots, and I can't upload saved frames onto here, just JPEG saved images. Customer however declined sensor, so there's no telling until I get a known good 4.0 come in the door again. Thanks for the help you guys. This helped clear up some unknowns for me, and hopefully some other younger techs too

                    Tom
                    "If you aim for nothing, you'll hit it every time!"
                    Zig Ziglar

                    Comment

                    • Crusty
                      Senior Member
                      • Dec 2007
                      • 2450

                      #11
                      Originally posted by Modis500
                      Crusty,

                      No driveability complaint, just intermittent hard start. I have saved numerous shots, and I can't upload saved frames onto here, just JPEG saved images. Customer however declined sensor, so there's no telling until I get a known good 4.0 come in the door again. Thanks for the help you guys. This helped clear up some unknowns for me, and hopefully some other younger techs too

                      Tom
                      Hey Tom
                      This isn't just for you but as you mentioned, some of the younger techs too.


                      You could stand on your head, save the screen from your computer, dump it into MS Paint, save it as a bitmap (I would use a jpg of tif or png myself) and then upload that....LOL...


                      Seriously though;

                      Play with your own vehicle. Set the amplitude and the time base to various settings and save both screen shots and record movies. Make use of SSC. It's an awesome supplement for the SnapOn tools. They're all just "tools" for gathering data. ShopStreamConnect makes it much much easier to manipulate what can very easily be captured from the vehicle.

                      Be consistent with the voltage setting then save a recording at one time base. Then stay with the same voltage setting and extend the time base. Then do it a 3rd and 4th time staying with the same voltage and different time bases.
                      There will be a "sweet spot" depending on the type of signal you're looking at for capturing enough information AND having a long enough period of time for a movie.
                      A 10 second movie will grab lots of "detail" but it would be difficult to save enough movies to actually capture anything.
                      On the other hand, a 10 minute movie may not have enough detail to actually capture an anomaly.

                      Once you get a "feel" for the right time setting, then try the same thing with some voltage settings. The scope "Presets" are a good starting point but sometimes I'll tweak the settings from there.

                      Quite often I'll start with 20-volts and 20-ms, take a look at what is on the screen and then fiddle the settings a bit until I can see what is usefull, and record from there.

                      Once you get a "feel" for what will be shown on a known good vehicle you'll become comfortable with hooking it up to a problem vehicle.
                      Your own vehicle will be there the next day for a different setup if you didn't quite get what you expected.
                      There are lots of ways you can manipulate SSC on a full size screen and see things easier AND have that same information saved for later review, even a couple of years from now.

                      Rich and his crew have done some really good things with SSC in the last couple of years.

                      Comment

                      • crackerclicker
                        Senior Member
                        • May 2008
                        • 400

                        #12
                        Originally posted by Modis500
                        Second set of screenshots are a '99 Jeep 4.0 CKP to CMP Correlation. Why does the Modis have a dirtier shot of the CKP sensor on the waveform at 200ms screenshot, but when you change the time to 20ms, it cleans up the waveform considerably?
                        The scope is aliased at that time base for that signal. Capture at a faster time base, then zoom out (anti-zoom) for more engine revolutions instead of capturing more engine revolutions (200ms timebase) without the ability to zoom in.

                        Comment

                        • Rich Shepherd
                          Snap-on D&I
                          • Nov 2006
                          • 553

                          #13
                          Originally posted by crackerclicker
                          The scope is aliased at that time base for that signal. Capture at a faster time base, then zoom out (anti-zoom) for more engine revolutions instead of capturing more engine revolutions (200ms timebase) without the ability to zoom in.
                          Here is some info:

                          Aliasing:

                          If you search for scope aliasing, you will find others.

                          Peak Detect will help with this:

                          See Modis Manual Appendix section on Peak Detect for some examples.

                          See the scope sample rate chart here:

                          Some more information on sampling and Peak Detect is in this chart.

                          Learn about essential electrical engineering bench equipment and how to use these tools to in diagnosing, troubleshooting and problem solving.

                          XYZ’s of Oscilloscopes, a nice resource for how things work.

                          Comment

                          • crackerclicker
                            Senior Member
                            • May 2008
                            • 400

                            #14
                            Hi Rich,

                            I had to use the Classic Verus specs since the OP is using an older MODIS. The Verus chart didn't have a 200ms sweep, so I fudged using the 250ms sweep. If I've loaded the numbers correctly, I'm thinking the OP's sample interval is somewhere around .4ms, which would be, coincidentally, the rise and fall time of one CKP pulse on this 4.0L Jeep at around 760rpm. Now, if I understand you correctly, and I have the numbers right, if the OP had Peak Detect on he would have captured a .0026ms sample interval with the max effective sample rate of 1.5Mhz, and would not have missed any CKP pulses.

                            Comment

                            • Rich Shepherd
                              Snap-on D&I
                              • Nov 2006
                              • 553

                              #15
                              Originally posted by crackerclicker
                              Hi Rich,

                              I had to use the Classic Verus specs since the OP is using an older MODIS. The Verus chart didn't have a 200ms sweep, so I fudged using the 250ms sweep. If I've loaded the numbers correctly, I'm thinking the OP's sample interval is somewhere around .4ms, which would be, coincidentally, the rise and fall time of one CKP pulse on this 4.0L Jeep at around 760rpm. Now, if I understand you correctly, and I have the numbers right, if the OP had Peak Detect on he would have captured a .0026ms sample interval with the max effective sample rate of 1.5Mhz, and would not have missed any CKP pulses.
                              Yes, you have the idea. Double check your math. It should be .00066 ms (1s / 1,500,000).
                              The 250 ms sweep in the Verus table should be 200. Must have been a typo.

                              Comment

                              Working...