Evap Moniters

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  • SnapOnKid
    Senior Member
    • Jan 2011
    • 870

    Evap Moniters

    I have had a few cars in recently that have me puzzelled when it comes to Evap repair. Maybe you guys have some tips or pointers or can at least tell me what I am doing wrong.

    First vehicale was I believe an 02 Dodge Caravan. Around 69k. A visual cheak revelled some broken ruber vacum hoses in the engine bay. after that was repaired. ran test again and it failed. Smoke check reveled the leak was coming from what I believe its called the bypass valve next to the canister. Its a round valve next to the canister just under the driverside floor board. Its very common. Sorry going from memory here.

    After replaceing the part then clearing the codes and running the test on the scan tool it showed the same code for the leak. I smoked it prior to the re-test to verify no other leaks in the system and the other componets seem to be working properly individually but I just could not figure it out. FWIW it was the middle of the day and about 75*

    The next vehical was an 04 Acura MDX. Around 71k This one had a 1456 code. It was 95* so I cleared the codes and ran the test. It passed but I figured the problem was still there so I waited till the next mornig when it was around 70*. Ran the test again and it failed... decided to tightened gas cap. failed again. Smoke check system and there was an issue with the two way valve next to the canister. So I replaced that and the solinoid attached to it incase it was not sealing properly. Smoked again no leakes. Clear and reset computer. Run the test and same thing, it failed again... This one I had no time to individually verify every other component was sealing properly but there were no obvious leaks.


    What else should I be looking for??? or maybe some one has some insight as to why I get a fail after replaceing parts and re-runinng the test??? I want to rule out user error and learn something If I am makeing a mistake.
    Last edited by SnapOnKid; 07-11-2011, 02:08 PM.
  • Joe Rappa
    Snap-on DSD
    • Aug 2007
    • 2050

    #2
    Originally posted by SnapOnKid
    First vehicale was I believe an 02 Dodge Caravan. around 100k. A visual cheak revelled some broken ruber vacum hoses in the engine bay. after that was repaired. ran test again and it failed. Smoke check reveled the leak was coming from what I believe its called the bypass valve next to the canister. Its a round valve next to the canister just under the driverside floor board. Its very common. Sorry going from memory here.

    After replaceing the part then clearing the codes and running the test on the scan tool it showed the same code for the leak. I smoked it prior to the re-test to verify no other leaks in the system and the other componets seem to be working properly individually but I just could not figure it out. FWIW it was the middle of the day and about 75*
    There are 2 valves on that vehicle that you need to close in order to leak check it. One of them is the LDP Bypass Valve. It has 2 large hose connections to it, one small vacuum line, and one open port. Use a hand held vacuum pump to close it. Check it closely for leaks. They get road dirt in the sometimes.
    The other valve you need to close is the LDP Valve. This is where the Vent Valve lives. An easy shortcut to close them is to:
    1) Connect your smoke machine to the test port and turn it on.
    2) Run the engine and command the EVAP Monitor to run with the scanner.
    3) As soon as the LDP is energized the system will pressurize, shut the car off, and check for leaks with the flowmeter/smoke.

    LDP Systems are a pain until you figure out how that pump works, then they're not bad at all.


    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

      #3
      As far as the MDX is concerned, that vehicle has a split system like a Nissan and a few other Asian Imports. When it leak checks, it isolates the fuel tank with a bypass valve, then does a leak check. It is checking the integrity of just the EVAP System, and not the fuel tank.
      Then it opens the bypass valve and rechecks the system, including the gas tank. The P1456 means it failed when checking the gas tank.
      Make sure the Bypass Valve is open when you leak check it. You can do this by simply seeing if smoke is coming out the filler neck. If not, you will need to open the bypass valve and do another leak check to confirm no leak.
      Also note that the P1456 is a pretty small leak. Are you verifying on the flow meter that there is no leak? Just checking.

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

      Comment

      • SnapOnKid
        Senior Member
        • Jan 2011
        • 870

        #4
        Originally posted by Joe Rappa
        As far as the MDX is concerned, that vehicle has a split system like a Nissan and a few other Asian Imports. When it leak checks, it isolates the fuel tank with a bypass valve, then does a leak check. It is checking the integrity of just the EVAP System, and not the fuel tank.
        Then it opens the bypass valve and rechecks the system, including the gas tank. The P1456 means it failed when checking the gas tank.
        Make sure the Bypass Valve is open when you leak check it. You can do this by simply seeing if smoke is coming out the filler neck. If not, you will need to open the bypass valve and do another leak check to confirm no leak.
        Also note that the P1456 is a pretty small leak. Are you verifying on the flow meter that there is no leak? Just checking.

        Joe
        Joe you are correct. I went back and looked up the vehical. 02 GrandCaravan We replaced the leak detection pump. I remember It was broken at the seem were the diaphragm is. I seal both of the vents when smoking the system.

        I do not block them when performing the functional test with the scan tool. Should I be doing that?

        Comment

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

          #5
          Originally posted by SnapOnKid
          I do not block them when performing the functional test with the scan tool. Should I be doing that?
          definitely not, only when smoking it. Also, so you know, when you run an EVAP Leak Check with the scan tool the vehicle only runs a .040" Leak Check. If the leak is less than that, it will not find it. The only way to know that the system is sealed for certain is to check it with your smoke machine.
          "You don't build a reputation on what you're going to do"
          Henry Ford

          Comment

          • SnapOnKid
            Senior Member
            • Jan 2011
            • 870

            #6
            Originally posted by Joe Rappa
            As far as the MDX is concerned, that vehicle has a split system like a Nissan and a few other Asian Imports. When it leak checks, it isolates the fuel tank with a bypass valve, then does a leak check. It is checking the integrity of just the EVAP System, and not the fuel tank.
            Then it opens the bypass valve and rechecks the system, including the gas tank. The P1456 means it failed when checking the gas tank.
            Make sure the Bypass Valve is open when you leak check it. You can do this by simply seeing if smoke is coming out the filler neck. If not, you will need to open the bypass valve and do another leak check to confirm no leak.
            Also note that the P1456 is a pretty small leak. Are you verifying on the flow meter that there is no leak? Just checking.

            Joe
            I sealed the entire system blocking the vents and smoked it. On both vehicals. I have a redline system here at this shop. I basically smoke it and watch to see if I have a leak. If it holds pressure and I don't see any visual signes of smoke. That should confirm the system it self is ok right? Then from there it would either be a vent valve or something???

            You will have to forgive me Joe I am self taught so if I am not doing something correctly its because of what some budy I worked for pointed me in the wrong direction. I have fixed more problems correctly then the idiots I have worked for. Unfortunately some of those were ASE master certified.

            Comment

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

              #7
              Originally posted by SnapOnKid
              If it holds pressure and I don't see any visual signes of smoke. That should confirm the system it self is ok right? Then from there it would either be a vent valve or something???
              Not seeing smoke and holding pressure are not guarantees that there isn't a leak. You have to have a flow meter if you want to verify it, unless someone knows a different way.
              "You don't build a reputation on what you're going to do"
              Henry Ford

              Comment

              • SnapOnKid
                Senior Member
                • Jan 2011
                • 870

                #8
                Originally posted by Joe Rappa
                Not seeing smoke and holding pressure are not guarantees that there isn't a leak. You have to have a flow meter if you want to verify it, unless someone knows a different way.
                Can you better describe the flow meter and how it would be properly used? I know there is one on the machine but I am not sure what you mean when your describing it. I can see how much psi is going in from the machine which is usually between 1/4 and 1/2 of 1psi

                Comment

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

                  #9
                  See Link: http://dl.dropbox.com/u/11961146/Leak%20Check.pdf
                  "You don't build a reputation on what you're going to do"
                  Henry Ford

                  Comment

                  • SnapOnKid
                    Senior Member
                    • Jan 2011
                    • 870

                    #10
                    Originally posted by Joe Rappa
                    Wow, that is very helpfull. Thank you!!! On our machine it has to be done manualy, but I believe if I had tested it that way I may have found my problem on both vehicals.
                    Last edited by SnapOnKid; 07-12-2011, 07:00 AM.

                    Comment

                    • Orevin
                      Senior Member
                      • Aug 2010
                      • 1110

                      #11
                      One of the first things I look at on Caravans/T&C are the fuel filler necks. The plastic insert cracks. I think we have replaced almost a dozen this year already:

                      caravan_filler_neck_02.jpg


                      Most of the cracks are smaller, but still visible.


                      I don't see many Honda fail with EVAP problems. However, I have found some gas caps leaking by removing the fuel filler hose from the tank and smoking up the neck.
                      -Kai-
                      Chicago, IL

                      Comment

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

                        #12
                        For every EVAP Leak code, your first order of business should be to see if it's really leaking. Plenty of times you will find that the PCM can't distinguish a leak from another problem.
                        I was just at a shop that has a very large fleet of GM pickups. They had several that had repetitive P0455, Gross Leak Codes. Every time they checked them, they were not leaking. We found that they all had bad purge valves. Here's what happened.
                        The PCM begins the EVAP System test by sealing the Vent Valve, and turning the Purge Valve on. If the Purge Valve is bad, no vacuum develops in the system. The PCM thinks it's a gross leak and sets a code, when no leak exists. I saw it on a Ford Explorer once too, but it's more common on the GMs.

                        By the way.....how can someone with a handle like SnaponKid have a coffee can for a smoke machine!?!? Tell me that!?!?


                        Orevin, great pic of a broken filler neck. May I steal that for my EVAP class?

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

                        Comment

                        • SnapOnKid
                          Senior Member
                          • Jan 2011
                          • 870

                          #13
                          Originally posted by Joe Rappa
                          ............By the way.....how can someone with a handle like SnaponKid have a coffee can for a smoke machine!?!? Tell me that!?!?

                          Joe
                          Sorry Joe I only bought 2 verus units, a cart, the cover, and some add on attachments. That was just this year from snap on. Not to mention what ever else I buy and carry on the truck account...

                          BTW I am only 31

                          Comment

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

                            #14
                            Originally posted by SnapOnKid
                            Sorry Joe I only bought 2 verus units, a cart, the cover, and some add on attachments. That was just this year from snap on. Not to mention what ever else I buy and carry on the truck account...

                            BTW I am only 31
                            Holy cow! Are you running 2 shops, or just have a big place?
                            "You don't build a reputation on what you're going to do"
                            Henry Ford

                            Comment

                            • SnapOnKid
                              Senior Member
                              • Jan 2011
                              • 870

                              #15
                              Originally posted by Joe Rappa
                              Holy cow! Are you running 2 shops, or just have a big place?
                              No its only around 3000sq ft. I was only supposed to be doing repairs. Nexthing you know I'm running the place... Again... Happens to me Alot, Only Problem is I don't get compensated for it.
                              Last edited by SnapOnKid; 07-12-2011, 09:07 AM.

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