How to find a Small EVAP leak without a smoke machine

hey there miss Dwayne Andrew fixes roof XCOM today I want to talk about a problem with the eave f system stands for evaporative emissions we're working on a 2012 Ford Explorer it's got about 96 thousand miles on it the driver came in and said the check engine light came on it seems to be driving fine there's no Luther complaint of any kind and we actually wrote tested it and confirm that check engine light on know the problem now when we scanned it we had code P oh four five six which indicates that there is a yvette small leak now the modern evap systems the computer that monitors this has the ability to detect whether or not the leak is a small medium or large and in this case it's a very small leak now the evap systems been around for a while and over time it's gotten more and more in fact the newest systems are called the enhanced 'back system and there's various methods and strategies as to how to find these leaks but it's those tiny little leaks that can be very frustrating in fact in the latest issue of motor Age magazine 2015 Jerry truly old wrote an article and the article was called finding the little ones about how to find the small even a police good article Jerry appreciated reading it and in this article he really covers a lot of ground on there how to find all kinds of things but especially the lilies he talks about the different strategies we use and sometimes the different levels of Diagnostics we have to go to I encourage you over read it Thanks for writing in Terry so there's all kinds of tools and techniques and strategies to find Eve appellees small ones and they're necessary we have to use them all but I want to talk to you today about one that I call the critical thinking method or how to find this small Eve athlete without a smoke machine so before I go any further I'm going to explain how the evap system works at least for this vehicle different manufacturers have different variations once we understand how it works then we'll look at the critical thinking method of trying to find the evap lis gasoline is a hydrocarbon or a liquid carbon but sooner or later that liquid carbon is going to turn into a vapor it heats up it cools down it sloshes around in the gas tank it's going to go from a liquid to a vapor at some point now those vaporized hydrocarbons can pollute the air if they escape to the air and we can no longer allow that so we have the evap or the evaporative emission system to control these vapors the basic elements of the fuel tank the gas cap the fuel tank pressure sensor the charcoal canister canister vent valve all of the lines that connect everything and the canister purge valve now the evap system collects these vapors from the fuel tank and it stores them in the charcoal canister but they can't stay there forever so the evap system also allows them to be drawn back into the engine and then mixed with the fresh air and burnt off in the combustion chamber but in order for this to work the system has to be airtight or there's no leaks now when the engine off we have no vacuum so the normal engine off state is the castor purge valve is closed or it's not been turned on it's sealed and the canister vent valve is open or venting that's the normal state it has not been turned on now the vapor in the field tank can now be stored in the charcoal canister but we have to be able to get it out of there and we will use engine vacuum to do it so when the evap system wants to draw the vapors from the charcoal canister it's going to open or energize the canister purge valve that's going to allow the vacuum and the engine then to travel now remember the canister vent valve was open and it's going to stay open and vapors can now travel from the charcoal canister all the way up to the engine now the evap system has a way of checking to make sure that it's working it's the enhanced monitors going to check for leaks but remember in order for this to work it has to have no leaks it has to be airtight now remember the system there is vacuum applied so when this system is going to check for leaks both of the valves have to close once they're closed the system is sealed to do this the canister purge valve will become de-energized or sealed and the canister vent valve will be energized or it will seal now the monitor can run and it monitors the pressure in the fuel tank pressure sensor so if the pressure drops a code will be set now to find a small leak you can use a smoke machine and sometimes we have to do that but there is another method that I call the critical thinking method now remember the monitor has applied vacuum and it has sealed it between the purge valve and the gas cap so the entire system is now sealed both valves are closed this purge valve and the canister vent valve now it's going to look for a leak somewhere between the first canister purge valve and the gas cap if there's a leak anywhere in there if the pressure bleeds down it will set the code now there's only two moving parts in this system the valves now the canister purge valve is a simple open or closed solenoid it's fairly easy to access and it's usually under the hood the canister vent valve is the same thing a simple open or closed cell noid but it's not so easy to access it's usually under the vehicle and in some cases you have to move shrouds that protect it now in EVAP system keep in mind that open or closed also means sealed or not sealed or leaking or not leaking now remember this vehicle has 96 thousand miles on it so how many times do you think that these valves have opened and closed thousands remember the valves are responsible to seal the system so it can be airtight and they have been opening and closing thousands of times by the time we get ninety six thousand miles on the vehicle now critical thinking tells me that the valves are the most likely to have failed so why don't we check them first now that we understand how the system works it's time to get our data we're going to use scanner and look at the computers data most of this can be done right from the drivers seat let me show you what I'm going to look for the first thing we're going to look at is the codes menu now you can see here there's 19 different possible modules or computers well we're going to look at the engine codes because that's where our Evette problem would be I can see that we have stored in the memory code p0 4 5 6 and explains that as an evap system leak very small leak our computers are pretty smart and they can monitor this system and they can tell if the leak is big little or somewhere in between our code says it's a very small leak so how does the PCM know that it's a small leak well to find this out let's you go to our scanner again and let's look under generic functions and then we're going to go to our monitors which is mode 6 now here we see the various sensors and monitors that the computer will do and what we want to look at is the evap monitors and if you'll notice there's three point zero nine point zero four point zero two well the large one is for a leak of point zero nine medium 0.04 and the small leak is 0.02 now we can go deeper and we can actually look at the large leak the 0.09 and if you notice down here it says the result is that it passed the medium leak is 0.04 and it passed and then the small leak is 0.02 and it failed so the computer has looked for a large and medium and a small the larger medium passed but the small leak failed that's why we have this code now the codes menu tells me the code but that's all right now I want to see more information so I have to go out of the code menu and go back and off now I'm going to go into the generic functions because what I want to look at is what we call free spring now what do I mean by freeze-frame well the remember the computer is actually running and controlling this car intercept monitoring all the systems including the evap system and remember it's saw a very small leak well what happens when it detects a problem it sets the code and the freeze-frame is all the data or a snapshot of all that data at the time that it saw the problem it set the code so when we go in here we can see what was going on when it happened now we've got a lot of information here and know one single thing is actually going to tell us what the problem is what we need to do is use our critical thinking think through the system understanding how it works and let's see what's going on and come to a judgment now you can see here that we've got engine speed or our rpm around 1,500 now idle is about 700 so this engine is running above idle but if we continue to look down on the right hand side will see that our engine coolant temperature sensor says it's about a hundred and seventy degrees now that's not startup this car has been running a while so the injury could actually build some heat our ambient air temperature is 60 59 degrees so it's not that cold out as I scroll down my data list I can see that the vehicle speed is zero miles per hour so the instant running about 1500 rpm but we're not going anywhere the image has been running a while because it's building up heat and the outside temperatures just a normal day the distance since the codes were cleared is 81 miles now in this case the driver did bring this into our shop and it was at the time when we were very busy and I couldn't get to it right then so I did tell them let me clear the codes tighten the gas cap and continue to drive it if the check engine light comes back on then we can look at it and see what's going on so it cleared the codes these driven 81 miles and now the check engine light has come back on now you can also see that with number of warmups he's driven this car three times or he started the car let it warm up to normal operating temperature three different times within 81 miles and it's finally set this code so you can see it doesn't reset that code immediately our fuel system says it's in open loop now open loop means that the system is actually being controlled by pre-programmed instructions you might say rather than actually controlling it by the data that's there we wanted to get into closely now open loop is when the code was sick so what does all this mean what does open loop mean now remember there are no other symptoms other than the check engine light an engine will always start an open loop and when you start the vehicle the RPM will rev up a little bit and then settle down the vehicle has been driven three times an 81 miles since I cleared the codes the evap monitor has identified a small leak the freeze-frame is telling me that the engine is warm not moving and the RPMs at 1500 so within 81 miles the vehicle has been driven shut off and restarted three times after the second shut off the internal is restarted again before it had cooled off and the code was set while in open loop and that code is for a small Eva plea

Channel: realfixesrealfast

Views: 1,501,990

Rating: 4.6772995 out of 5

Keywords: Ford, EVAP, evap, evaporative emissions, smoke machine, critical thinking, evap leak, small leak, realfixesrealfast, real fixes real fast, engine diagnostics, Vehicle Emissions Control, Smoke, Automobile (TV Genre), How-to (Website Category), Do It Yourself (Hobby)

Id: Pg4AEe_xWo4

Length: 13min 6sec (786 seconds)

Published: Wed Aug 26 2015