How to find a Small EVAP leak without a smoke machine Part 2

now we understand how this system works we looked at all the data and we know we're looking for a small leaf it could be anywhere but the easiest and most accessible place to start is the purge valve remember the valves are responsible to seal the system so it can be airtight and they have been opening and closing thousands of times and on this Ford Explorer it happens to be right in the engine bay it's pretty easy to get to we just have to lift off this engine cover there's a couple fasteners to hold that down and then that's right next to the intake now the canister purge valve is a simple open or closed solenoid now the engine creates the vacuum by the Pistons coming down making the negative pressure inside the engine that vacuum is that coming from the intake and the purge valve is actually bolted right to the top of the intake so the vacuum comes from the intake and the purge valve then once it is commanded by the computer to open it allows that vacuum to travel to this hard plastic tube all the way back so this is our easiest access point and it's the first thing we want to check now a lot of the older and first systems out there you should use just rubber lines but the newer cars use these hard plastic molded and sealed vacuum lines they're less likely to leak but that's possible then let's look at the valve first the vacuum that's in this intake needs to get through this valve so it can travel back to the canister it's got a simple little electrical connector shut that out of the way and there's a little green clip that locks it in place once you get the glean green clip out then the hard plastic line the molded plastic line can come off will just tuck that off out of the way a little bit too so let's take this valve off and see what we can find there's just too little number eight volts on it and now the valve will just simply lift off so this canister purge valve sits on top of the intake and vacuum is applied here and then when the PCM opens this valve vacuum then can go through here so technically this should be sealed and you shouldn't be able to go through it or some through it making vacuum so let's see if I go to the vacuum side you know it almost feels to me like it comes coming through there if I go to this side I can hear just a little bit of seepage here so to show you a little bit better on the video because you can't hear everything I'm going to use this vacuum gauge now this is a gauge that shows vacuum or pressure and I'm going to hook it into the output side of this valve so when I blow through this side you shouldn't see any change let's see but when I try to suck through it or create a vacuum you can actually see it moving so that Valve inside there is not blocking it off completely it's leaking let's look at a brand new one and compare it this is the old one and I've got my brand new one from the parts store and we'll hook it up the same way I'm going to put it in here then if we watch my gauge when I try to blow through it no movement on the gauge and when I try to draw a vacuum on it don't move it on the gauge again let's go back to the other one when I try to draw a vacuum on here or when I bow through it so this old vacuum control valve or the vacuum purge valve is leaking it's not leaking a lot because I can't go through really heavy but it's leaking a little and our code says we have a little leak a small leak this is leaking so our critical thinking is telling me that this could be the problem at least is a problem whether or not if the whole leak I don't know yet but this is leaking so what we're going to do is replace this and then we're going to let the computer that found the leak in the first place test this whole system again and tell us whether or not we fixed it if we did there should no longer be a little leak if we didn't we'll need to keep looking now everything we've got to repair me it's time to go for a drive now the computers in these vehicles are very good at what they do they monitor the system all the time and if there's a problem of course they'll turn the check engine light on we make our repair why not let the computer that is monitoring it tell us that the repair has been made that the problem is no longer there so what we will do is go for a drive let the evap system monitor run and just like it told us earlier that we have a small leaf we should be able to let it run and it will tell us that that small leak is no longer there or a problem phenophase so now we know that the computer has rotted system is checked everything and now it's reporting that all systems have passed there's no more small leak so how does the PCM know that the leak is fixed well it runs its tests again and it has the large leak test and it passed the medium leak and it passed and then it runs the small leak and it passed but how well did it pass this is when it passed let's look at the screen back when it actually failed the small leak failed notice that it has a value of 0.75 but the maximum that it would allow is point 4 0.75 is a lot greater so the value was so high that it failed this test but now when it passes we have a value of zero so not only did it does it not leak it doesn't leak at all that's why it passed the test so this confirms that we have fixed the problem another arm is to used actually closed the purge valve and seal it closed the vent valve and seal it but a vacuum in the system and watch the fuel tank pressure sensor and watch to see if the pressure holds but that's what the computer is doing anyway that's where this job is so why not let it do its job and tell us that we've made to repair so once again it's our knowledge our critical thinking that has helped us make this repair sure there are tools and equipment strategies and all kinds of things we can do but probably the most effective thing that we can do is think it through

Channel: realfixesrealfast

Views: 892,696

Rating: 4.9111447 out of 5

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Id: oeNqJtwmFw8

Length: 8min 47sec (527 seconds)

Published: Wed Aug 26 2015

Reddit Comments

[u/Telito]

Very informative