Oooh the pressure!

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

    #16
    Originally posted by Crusty
    HMMMMM

    "in H2O "

    interesting observation.
    Thank you, again, for posting somthing that is so helpful. I liked it better when you actually contributed something to this website instead of complaing chronically.
    As I've said many times in the past, I don't speak for Snap-on, but I can make a pretty educated guess as to why you won't see the units changed from "Hg to 'H2O in the Snap-on Scanners: Because it would be useless to do so. Even if the units were changed, they still wouldn't match what an actual pressure/vacuum gauge reading measured. The zero readings will be correct, but any time vacuum or pressure is added, the reading would drift from the correct value. So changing the units doesn't help anything. I am not sure why you are so stuck on this.

    As for missing PIDs, anything you would like added to the scan tool, please post a message in the "What do I want added" Forum. Give the 1st 10 digits of the VIN, and plainly state why you need it. Snap-on wants to correct any missing data from the data stream if it is useful Data. Complaining like you did in this post, and most every other post on this Forum won't get you what you need, but doing it the right way will.

    P-L-E-A-S-E return to being a useful contributor to this website.

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

    Comment

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

      #17
      Originally posted by greasybob
      I had an old NVLD from an 05 Dodge Neon, so I opened it up and here is the autopsy report with my attempt to explain it's functions. If there are any mistakes or I left anything out please feel free to add to it. http://www.youtube.com/watch?v=0QCLqXx6SGI It seems to me that if pressure were to start to build in the tank that the larger diaphram that closes the micro switch when there is vacuum, would push down on the solenoid valve on the bottom which would then release the pressure. Even though the pressure would be the same on both the diaphram and the valve, the larger area of diaphram would still over come the pressure on the valve.
      Hey Bob,
      See this link to my dropbox account. If you have Powerpoint, view it in full screen mode to see the operation of the NVLD Valve.
      Pressure definitely doesn't move the diaphragm, because it never gets a chance to build up. The checkvalve makes sure of that. However, when vacuum is generated, it lifts the diaphragm (because the top of the diaphragm is connected to the canister pressure through a passage in the solenoid housing).
      Thanks to Glenn for putting this slde show together.



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

      Comment

      • Crusty
        Senior Member
        • Dec 2007
        • 2450

        #18
        Originally posted by Joe Rappa
        Thank you, again, for posting somthing that is so helpful. I liked it better when you actually contributed something to this website instead of complaing chronically.
        As I've said many times in the past, I don't speak for Snap-on, but I can make a pretty educated guess as to why you won't see the units changed from "Hg to 'H2O in the Snap-on Scanners: Because it would be useless to do so. Even if the units were changed, they still wouldn't match what an actual pressure/vacuum gauge reading measured. The zero readings will be correct, but any time vacuum or pressure is added, the reading would drift from the correct value. So changing the units doesn't help anything. I am not sure why you are so stuck on this.

        As for missing PIDs, anything you would like added to the scan tool, please post a message in the "What do I want added" Forum. Give the 1st 10 digits of the VIN, and plainly state why you need it. Snap-on wants to correct any missing data from the data stream if it is useful Data. Complaining like you did in this post, and most every other post on this Forum won't get you what you need, but doing it the right way will.

        P-L-E-A-S-E return to being a useful contributor to this website.

        Joe
        OK.
        Make sure you take your calculator with you along with your scan tool so you can take the mmHG displayed by the scan tool to measure against the values described in the factory service manuals and diagnostic charts so you can multiply the scan tool value by 0.5353.

        All I had done was make an observation that inH2O was used as a unit of measure by someone posting here, the same unit of value factory service manuals use in a great many instances.
        I also noted that someone else used the expression "necessary pids" and that they were missing.

        So, it's OK for anyone else to make those two observations but not me??

        BTW. SnapOn HAS been given the vin's a great many times, regarding "necessary" missing pids and values displayed, even with photographs of factory scan tools displaying the pids in the correct values.
        (along with other errors and ommisions)

        BTW; "they still wouldn't match what an actual pressure/vacuum gauge reading measured. The zero readings will be correct, but any time vacuum or pressure is added, the reading would drift from the correct value. So changing the units doesn't help anything. I am not sure why you are so stuck on this."
        Two days ago, I checked a vehicle where the correct values were displayed and the pid was on the scan tool. I had an old fashioned guage hooked up to the system. Pumped 7-inH20 with a hand held mityvac. Compared the pid reading to the guage. Matched values. And no, they didn't "drift" with the system sealed, confirming a good fix of that vehicle. Every time I bled out a couple of inH2O the scan tool matched the guage value. Everytime I added a couple of inH2O, the scan tool and the guage again matched. BOTH the guage and the scanner values did NOT drift from where I set them for over 5 minutes. I guess I must have a broken scanner and a broken guage.
        Last edited by Crusty; 05-01-2011, 04:41 PM.

        Comment

        • greasybob
          Senior Member
          • May 2008
          • 1590

          #19
          Thanks the slide show, more good information. Part of the process of solving a problem is understanding how the proper function is supposed to work. Another part is knowing the pass/fail parameters. This should help with both. I know it doesn't sound the most sanitary but when you hold the NVLD up to your mouth you realize it doesn't take much pressure to get air to move in either direction. I noticed that after I split it in half and plugged the passage that allows air to go above the diaphram that then I could no longer blow into the port that is marked (goes to the) canister. Thats where I came to the conclusion that the diaphram also plays a role in venting the pressure by pushing down on the vent valve. Just another note, if you look carefully at the top of the NLVD there is an adjustment (calibration) screw that has been sealed off.

          Comment

          • Crusty
            Senior Member
            • Dec 2007
            • 2450

            #20
            Originally posted by Joe Rappa
            Thank you, again, for posting somthing that is so helpful. I liked it better when you actually contributed something to this website instead of complaing chronically.
            As I've said many times in the past, I don't speak for Snap-on, but I can make a pretty educated guess as to why you won't see the units changed from "Hg to 'H2O in the Snap-on Scanners: Because it would be useless to do so. Even if the units were changed, they still wouldn't match what an actual pressure/vacuum gauge reading measured. The zero readings will be correct, but any time vacuum or pressure is added, the reading would drift from the correct value. So changing the units doesn't help anything. I am not sure why you are so stuck on this.

            As for missing PIDs, anything you would like added to the scan tool, please post a message in the "What do I want added" Forum. Give the 1st 10 digits of the VIN, and plainly state why you need it. Snap-on wants to correct any missing data from the data stream if it is useful Data. Complaining like you did in this post, and most every other post on this Forum won't get you what you need, but doing it the right way will.

            P-L-E-A-S-E return to being a useful contributor to this website.

            Joe
            P-L-E-A-S-E GO LOOK UP P0446-!!!!!!!! and actually READ the values in the diagnostic flow charts-!!!

            Take your pick, here's a list of vehicles.....and you might need the vacuum pressure chart along with your calculator.

            And the problem isn't the "HG to 'H20, (inches of mercury to feet of water) it is mmHG vs inH20-!

            (Pardon the date/time stamp on the last 3 pics, the batteries in my camera went dead from documenting the ACTUAL VALUES used by the manufacturer of these vehicles-!)
            Attached Files

            Comment

            • Crusty
              Senior Member
              • Dec 2007
              • 2450

              #21
              Originally posted by Joe Rappa
              Thank you, again, for posting somthing that is so helpful. I liked it better when you actually contributed something to this website instead of complaing chronically.
              As I've said many times in the past, I don't speak for Snap-on, but I can make a pretty educated guess as to why you won't see the units changed from "Hg to 'H2O in the Snap-on Scanners: Because it would be useless to do so. Even if the units were changed, they still wouldn't match what an actual pressure/vacuum gauge reading measured. The zero readings will be correct, but any time vacuum or pressure is added, the reading would drift from the correct value. So changing the units doesn't help anything. I am not sure why you are so stuck on this.

              As for missing PIDs, anything you would like added to the scan tool, please post a message in the "What do I want added" Forum. Give the 1st 10 digits of the VIN, and plainly state why you need it. Snap-on wants to correct any missing data from the data stream if it is useful Data. Complaining like you did in this post, and most every other post on this Forum won't get you what you need, but doing it the right way will.

              P-L-E-A-S-E return to being a useful contributor to this website.

              Joe
              P-L-E-A-S-E actually read the requirements for running the DTC and the conditions for setting the DTC-!!!

              The MISING PIDS WILL AFFECT the pressures and the on-board self diagnostics, no matter what vehicle is being tested or whether the system is a NVLD system or not.

              Here are 5 of the above noted vehicles. The fuel tank level PERCENT varies from year to year and from vehicle to vehicle, depending on what parameters the manufacturer designated as the window of operation.

              Not all of the vehicles support the Evap-Service-Bay-Test so, as noted at the bottom of the last picture....DTC P0446 runs ONCE per COLD START when the above conditions are met......so we have ONE, and only ONE shot at the system completing all it's self tests under normal operating conditions.
              SOME of the newer NVLD systems require as many as 17 hours of engine off time before they will self test again. If ANY of the above MISSING PIDS is out of range, the systems will not self test.
              Ya, you can run the drive cycle to satisfy the "State Emissions" but...Is the vehicle actually fixed???. Only real world normal operating conditions (the acid test) will truly determine if the vehicle is properly fixed so the on-board self tests do not set a code some later day.

              Can it be any clearer why these missing pids and correct scale values are important and relevant to....OOOOOOH THE PRESSURE-!

              (but I'm only complaining and not concerned with actually fixing vehicles)
              Attached Files

              Comment

              • SnapOnKid
                Senior Member
                • Jan 2011
                • 870

                #22
                Crusty you should know better. Snap On doesn't use Alldata even though most of it is a direct copy of the OEM factory service manual and its much easier to navigate.

                And thanks for learning me something new with that calculation chart. I always wondered how you got those corrections but I was to lazy to look it up.

                Comment

                • crackerclicker
                  Senior Member
                  • May 2008
                  • 400

                  #23
                  crusty (and anyone else interested),

                  here's a handy program for conversions. doesn't have "h20, but still usefull.

                  Convert is a free and easy to use unit conversion program that will convert many of the most popular units.

                  Comment

                  • Crusty
                    Senior Member
                    • Dec 2007
                    • 2450

                    #24
                    Originally posted by SnapOnKid
                    Crusty you should know better. Snap On doesn't use Alldata even though most of it is a direct copy of the OEM factory service manual and its much easier to navigate.

                    "But the Factory service manuals could be wrong".....ya, right, for about 10 years.... OCCASIONALLY they'll make reference to some metric values, but you really shouldn't have to take a conversion chart and a calculator with you to convert what the scanner displays in order to check against what the service manual tells you to check for.
                    No matter which system you are working on, there is a DIRECT RELATIONSHIP between TEMPERATURE and PRESSURE. If there wasn't, the EONV and the NVLD evap systems wouldn't work at all (to say nothing of A/C either-ROFLMAO)
                    EVERY evap system I've looked into also takes into consideration the fuel tank level. If it is near empty, there is a much larger vapour volume, and if it near full, there is a much smaller vapour volume. One way it will take longer to either create a vacuum or a pressure, and the other it will take a much shorter time to create either a vacuum or a pressure. The borderlines of 15-PERCENT and 85-PERCENT, or as shown in one case the 12.5-PERCENT and the 87.5-PERCENT are CRITICAL NECESSARY PIDS.
                    If we know (by looking up the system we're working on in the FACTORY service manual) what the break points are for a system, it may be just a matter of waiting another twenty minutes for a vehicle to cool off just a little bit more, or possibly just putting a jack under one end of the vehicle to change the fuel tank level PERCENT READING one or two points SO WE CAN TEST THE VEHICLE AND HAVE THE SYSTEM ACTIVATE INSTEAD OF ABORTING THE SELF-TESTS-!!!
                    There have been times when I have purposely selected a particular parking area to let a vehicle cool down for several hours and have the fuel tank angle change just two or three degrees, so on the next cold start, the vehicle sees that it is within the self test range. But we can't do that if we can't read the pids.
                    Sorry Mr Smith, we'll have to wait another 17 hours for your vehicle to allow the next step of the diagnosis.
                    Sheesh-!!


                    And thanks for learning me something new with that calculation chart. I always wondered how you got those corrections but I was to lazy to look it up.
                    JFYI, I've noticed that mmHG and TORR are the same scales in most of the charts and conversion calculators that I have found. Ain't the metric system just great??-!!-LOL
                    Even when GM makes reference to either kpa or mmHG, they ALWAYS include a reference to INCHES OF WATER COLUMN-!!!!

                    Comment

                    • Crusty
                      Senior Member
                      • Dec 2007
                      • 2450

                      #25
                      Originally posted by crackerclicker
                      crusty (and anyone else interested),

                      here's a handy program for conversions. doesn't have "h20, but still usefull.

                      http://joshmadison.com/convert-for-windows/
                      Thanks for the link.
                      It was funny, the site said Josh Madison is 13,777 days old......LOL
                      That makes him a little under 40.....he's ALMOST a crusty old fxrt-!! (there 'net-nanny)

                      Comment

                      • Steve6911
                        Moderator
                        • Feb 2007
                        • 2168

                        #26
                        Originally posted by Joe Rappa
                        Thank you, again, for posting somthing that is so helpful. I liked it better when you actually contributed something to this website instead of complaing chronically.


                        P-L-E-A-S-E return to being a useful contributor to this website.

                        Joe

                        THANKS JOE! Could not have said this better myself!!!

                        The "net-nanny"

                        Comment

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

                          #27
                          Originally posted by Crusty
                          P-L-E-A-S-E actually read the requirements for running the DTC and the conditions for setting the DTC-!!!
                          Again, name the specific vehicle, and the missing PID(s).
                          "You don't build a reputation on what you're going to do"
                          Henry Ford

                          Comment

                          • Crusty
                            Senior Member
                            • Dec 2007
                            • 2450

                            #28
                            Originally posted by Joe Rappa
                            Again, name the specific vehicle, and the missing PID(s).
                            Take your pick. ANY GM 2000 to 2005
                            ECT- IAT- FTL%- inH2O
                            No serial number required, they're ALL missing pids-! The same ones in the pictures from the factory manuals, or doesn't your MOD show them?
                            The same pids that affect any of the other Asian, European or North American vehicles when they self test the EVAP systems.

                            Comment

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