2007 Impala P0442 EVAP Small Leak

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  • 19mopar
    Member
    • Oct 2010
    • 38

    2007 Impala P0442 EVAP Small Leak

    07 Impala P0442 EVAP small leak. VIN 2G1WB55K779254969
    Vehicle came in with P0442 code stored. Vehicle has a 1/2 tank fuel. Removed line from purge solenoid (no service port) and smoke tested system untill smoke came out of filler tube then put fuel cap on. No smoke seen and no leak under pressure. Removed smoke and sealed system and no drop in fuel tank pressure pid. Performed purge/seal test with verdict and there was a slow drop in vacuum according to fuel tank pressure pid. Pinched off hose to vent valve to eliminate valve, still a slow drop in vacuum. Vacuum tested purge solenoid, ok. Applied vacuum with a hand held pump to system at purge solenoid line and monitored fuel tan pressure pid and still showed drop in vacuum. Have a fuel cap (GM) on order and ordered a blue point universal fuel filler adapter to smoke test from the tube to see if a leak can be found that way. Seen Bob's post and others on smoke testing from the filler neck. Wondering if the roll over valve in the filler tube could let smoke out of the top of filler tube untill the cap is installed then it would seal under pressure and not be able to detect a leaking cap or crack filler neck like the post that Bob nicely illistrated.

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

    #2
    Hi Darren,
    From the sounds of it, you may have a cap that leaks under vacuum but not under pressure. Remember they have 2 valves in the just like a radiator cap. It's possible for one to be bad and not the other.
    Does the flow meter indicate a leak when you pressure test it? It's possible to have a leak that's not easy to detect with smoke. If your smoke machine can tell how big a leak is, maybe just leak check it once more to be sure.

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

    Comment

    • 19mopar
      Member
      • Oct 2010
      • 38

      #3
      I have the OTC smoke tester that does have a flow meter on it. The ball decends to the bottom of the meter and stays there indicating no leak detected. The blue point adapter is not available until late june so i bought an aftermarket cap and i am going to drill a hole in the top like Trindaddy explained in a previous post. I did notice that on this after market cap before drilling, that it takes a very small amount of vacuum to unseat the seal but if pressurized by mouth, it holds. Used a hand held vacuum pump and won't register vacuum on guage before it vents. Is this common or just an aftermarket cap not performing properly like a GM one.

      Thanks
      Darren.

      Comment

      • Trindaddy
        Senior Member
        • Jan 2010
        • 339

        #4
        The one i used was a Stant Darren, the line 1/4 in. ID reg fuel line. The line will go all the way into the cap (i think remove the vent guts, spring etc. Its been a while) and add a little glue. Will work great. I gotta buy a new camera, my daughter dropped mine! If you had smoke at the filler though, sounds like you might not need it for this one. Still good to have.
        Last edited by Trindaddy; 06-06-2011, 04:01 PM. Reason: brainfart

        Comment

        • Crusty
          Senior Member
          • Dec 2007
          • 2450

          #5
          I've used STANT caps without issues several times. Just a silly-azz suggestion......(remember I'm from Canada-LOL).... if you can get the neck clean enough, try taping off the filler with.....DUCT TAPE-!!! Seals both pressure and vacuum at the scale levels the evap system applies. Even in mmHG-!! LOL

          Comment

          • Orevin
            Senior Member
            • Aug 2010
            • 1110

            #6
            Darren,

            When you perform the Purge/Seal test, draw vacuum until the FTP sensor reads about 3.5V. If the tool locks out before that, try 3V. If you then seal the system and the sensor voltage drops less than 0.40V within a minute, the system is sealed.

            HTH.
            -Kai-
            Chicago, IL

            Comment

            • eddiesverus
              Senior Member
              • Dec 2008
              • 414

              #7
              Evap Test

              Guys also keep in mind that when performing the purge seal test on a hot vehicle you wil not get an acurate test result due to fuel expansion making you beive theres a leak. thats whats why the PCM runs the leak on a cold start. replace the fuel cap and run the service bay test if it passes then your done. let the PCM decide if theres a leak or not. by using the smoke tester and if the flow ball stayed at the bottom then thiers no leak. use mode6 test result to comfirm at what level it failed. then when you run the service bay test recheck mode6 results. good luck..
              Hard Work, commitment, Honesty and not giving up is what Makes us better Tech's

              Comment

              • 19mopar
                Member
                • Oct 2010
                • 38

                #8
                Thanks for the replies guys. I got the new cap today and had customer drop vehicle off on their lunch hour. Customer called and needed car by 4:00. Let vehicle sit and at 3:30 replaced gas cap (GM) Smoke tested system and system passed. Tried to run EVAP service bay test, but being close to ninety degrees today in ND the vehicle didn't drop below the 86 degree ECT threshold to start test. Did perform purge/seal test and got FTP pid to 3.4V and sealed system. FTP pid dropped to 3.15 Volts within 60 seconds. Sent customer on her way and will get vehicle dropped off later this week (hopefully in the AM and it is suposed to be cooler, highs 65-70) and will run service bay test again to verify. Thanks again for all the replies and will post when vehicle comes back.

                Comment

                • Orevin
                  Senior Member
                  • Aug 2010
                  • 1110

                  #9
                  Darren,

                  When the vehicle comes back, keep in mind that the "Service Bay Test" involves some driving, 30 minutes and about 10 miles. Then you have to turn off the car and let it sit for half an hour or so, the PCM runs the EONV part during that time. Plan about 1.5 hours for the test.
                  -Kai-
                  Chicago, IL

                  Comment

                  • Crusty
                    Senior Member
                    • Dec 2007
                    • 2450

                    #10
                    Originally posted by Orevin
                    Darren,

                    When the vehicle comes back, keep in mind that the "Service Bay Test" involves some driving, 30 minutes and about 10 miles. Then you have to turn off the car and let it sit for half an hour or so, the PCM runs the EONV part during that time. Plan about 1.5 hours for the test.
                    Also make sure the fuel tank level percent is well inside the 15% to 85%. Fuel slosh could tip over the limit and abort the test. Just sayin.....

                    Comment

                    • 19mopar
                      Member
                      • Oct 2010
                      • 38

                      #11
                      Thanks for the tips. The first Service bay test i ran was on a 08 Impala that was on our lot for sale was on a learning experience. First i was wireless with the verdict and it said it could take up to 10 min running between 1800 and 2200 rpm. sat in vehicle for 20 min and still said it was testing and screen wouldn't change. Aborted test and waited till the next day. Used verdict with usb cable attatched to S3 and test ran fine. After 8-10 min at 2100 then drove 10 miles and then let sit. Don't know if it was a glitch or not but in the future i think i will use the usb cable because of the time required and if it doesn't run properly then vehicle will need to sit untill peramiters are met again.

                      Comment

                      • Crusty
                        Senior Member
                        • Dec 2007
                        • 2450

                        #12
                        Originally posted by eddiesverus
                        Guys also keep in mind that when performing the purge seal test on a hot vehicle you wil not get an acurate test result due to fuel expansion making you beive theres a leak. thats whats why the PCM runs the leak on a cold start. replace the fuel cap and run the service bay test if it passes then your done. let the PCM decide if theres a leak or not. by using the smoke tester and if the flow ball stayed at the bottom then thiers no leak. use mode6 test result to comfirm at what level it failed. then when you run the service bay test recheck mode6 results. good luck..
                        The automated EONV system test starts with a cold start (IF the vehicle is within the self test parameters), then the PCM wants to see a number of miles driven and an amount of time passed and coolant temperature and fuel level, etc.
                        Then upon shut down the PCM can stay awake for as much as 40 minutes after key off while the system seals, watches the FTP rise to a pressure (with the undercar heat expanding the vapours), then it wathces the FTP slowly drop down to a vacuum as it cools.
                        THEN it is satisfied that no leak exists.

                        You're right if you're doing a manual purge/seal test but it also depends on how hot the vehicle is. If it has only run 5 or 10 minutes in the shop after sitting all night, there might not be enough undercar heat to build pressure by heating the vapours.

                        THAT'S WHY seeing ALL the pids is important........
                        BWTHDIK.....

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