If you plug the line, the downside is you have no reserve supply of vacuum. Under certain driving conditions, the HVAC system may randomly direct air to different vents for short periods, then go back to the correct settings. If you have 4x4, there may be times when the front hubs will unlock or brief periods. If you can live with that, then plug away.
As a side note, any type of canister will work for this. I've heard of some guys making vacuum reservoirs out of PVC pipe.
Thank you for posting this image, I believe it helped me with my loose hose and P0440 Code, Only time will tell but this seems to have fixed the issue with my 00' Bravada AWD.
Purchased this blazer runs perfect. It have no hot heat... Someone suggested looknat vacuum lines and low and behold one of the vacuum lines at the t is plugged w a screwdriver...cannot for the life of me find where it goes to....it's 28 degrees I have kids and we are cold....
Purchased this blazer runs perfect. It have no hot heat... Someone suggested looknat vacuum lines and low and behold one of the vacuum lines at the t is plugged w a screwdriver...cannot for the life of me find where it goes to....it's 28 degrees I have kids and we are cold....
Hi. I am brand new to this forum. I have searched so many places and spoken with many people. this is my issue:
My gas mileage is terrible. I got the code p0440 which I have looked up and got this answer from someone apparently knowledgeable
"This code means evap system is leaking. The most common causes are vent solenoid, fuel cap, or rusted filler neck. You can activate the vent solenoid to make sure you can't blow through it, if you still can blow through it then replace. Next step would be visual inspection of filler tube and evap lines back by canister under rear of vehicle. IF both look good replace fuel cap. If problem still exists you would want to have a smoke test done to see where leak is coming from"
A lot of people say it's the gas cap. I got a new one. Still have same problem and still have check engine light on. Today, while looking under the hood of my 2001 Blazer 4door 4wd 4.3 v6 vortec in the for top right part of the engine compartment I saw a white ****** connector with a loud hissing sound coming from it. I put my finger to it and realized it is a vaccum. Right beside it I saw a small rubber hose that looks like it should be connected to it as it's about the right size but it was corroded and not clean/flat on the end. I cut it back to the point where it was flat and put it onto that white vaccume device which by the way Tee's off towards the engine on another hose. I have asked people and looked up hour long videos on evap emissions trying to understand what this specific hose is for and can't figure it out. I'm hoping that reconnecting it solved the problem and hundreds of dollars at the mechanic. Can anyone provide any advice? I will share a picture this is the white part on the left with he vacuum and the corroded rubber hose disconnected.
.
The purpose of the evap system is to prevent fuel vapors from escaping into the atmosphere and to improve fuel economy. This is accomplished by controlling fuel tank venting, capturing fuel vapors, sending the trapped vapors to the engine to be burned, and to routinely test this system to make sure that it is not leaking.
The gas cap is sealed and a vent tube goes from the gas tank to a charcoal cannister then the CC is vented to the atmosphere through a normally open vent solenoid. Another line goes from the cannister to a normally closed purge solenoid near the engine intake.
The vent solenoid is normally open so that the fuel tank can fill and be drained with pressure relief to the atmosphere. The charcoal cannister captures fuel vapors so that this venting does not release fuel vapors to the delicate outside world. So why would you have trouble filling your gas tank? Because there is no proper venting to the atmosphere. Why can this happen? The normally open vent solenoid valve is faulty and closed. One of the lines is blocked with insect crud or dust. The charcoal cannister is blocked. Some vehicles are equipped with a rollover valve where the vent hose leaves the gas tank on its way to the CC. This check valve is sometimes integrated into the tank pressure sensor. As a side note, there may be an antisiphon valve as part of the filler neck that can swell or otherwise fail and that can prevent filling because the filling process is blocked, not because the tank will not vent to allow room for the fuel. The filler neck is simply no fully open.
The lines to the purge valve and the purge valve have nothing to do with a no fill issue because the solenoid is normally closed. A failure would only help this situation but cause other problems. The purge valve is opened at set intervals to draw the stored fuel vapors from the CC to the engine intake to be burned. Again, the vent solenoid is open as it almost always is.
The routine testing involves closing the vent valve (the only time it is closed) and either pressurizing the system or temporarily opening the purge valve to create a vacuum, then close both valves and see if there is a leak. This test is done with the engine running and uses either engine vacuum or a separate pressure pump. Some vehicles also use the natural change in pressures after the vehicle is off and at rest. This is one reason why the VCM may stay on for a while on some vehicles.
What do the failure codes mean? When the test was conducted, the temporarily sealed system would not hold vacuum/pressure so something is leaking: hose, valve, cannister, tank, gas cap. The leak is usually described as either large or small to aid in the diagnostics.
Now what does all of this mean for you? Usually an evap code says that the vehicle has failed the system integrity test which means that you are polluting the atmosphere with gas fumes and/or you cant easily fill the gas tank. Usually this has zero effect on engine performance because that entire system is isolated from the engine by the purge solenoid valve which is normally closed. The exception to this would be a purge valve that is stuck open, is erroneously being commended open or is leaking at the engine intake. This would manifest as a standard issue vacuum leak and can be proven as such. Let me know if you need help diagnosing any of this.
The purpose of the evap system is to prevent fuel vapors from escaping into the atmosphere and to improve fuel economy. This is accomplished by controlling fuel tank venting, capturing fuel vapors, sending the trapped vapors to the engine to be burned, and to routinely test this system to make sure that it is not leaking.
The gas cap is sealed and a vent tube goes from the gas tank to a charcoal cannister then the CC is vented to the atmosphere through a normally open vent solenoid. Another line goes from the cannister to a normally closed purge solenoid near the engine intake.
The vent solenoid is normally open so that the fuel tank can fill and be drained with pressure relief to the atmosphere. The charcoal cannister captures fuel vapors so that this venting does not release fuel vapors to the delicate outside world. So why would you have trouble filling your gas tank? Because there is no proper venting to the atmosphere. Why can this happen? The normally open vent solenoid valve is faulty and closed. One of the lines is blocked with insect crud or dust. The charcoal cannister is blocked. Some vehicles are equipped with a rollover valve where the vent hose leaves the gas tank on its way to the CC. This check valve is sometimes integrated into the tank pressure sensor. As a side note, there may be an antisiphon valve as part of the filler neck that can swell or otherwise fail and that can prevent filling because the filling process is blocked, not because the tank will not vent to allow room for the fuel. The filler neck is simply no fully open.
The lines to the purge valve and the purge valve have nothing to do with a no fill issue because the solenoid is normally closed. A failure would only help this situation but cause other problems. The purge valve is opened at set intervals to draw the stored fuel vapors from the CC to the engine intake to be burned. Again, the vent solenoid is open as it almost always is.
The routine testing involves closing the vent valve (the only time it is closed) and either pressurizing the system or temporarily opening the purge valve to create a vacuum, then close both valves and see if there is a leak. This test is done with the engine running and uses either engine vacuum or a separate pressure pump. Some vehicles also use the natural change in pressures after the vehicle is off and at rest. This is one reason why the VCM may stay on for a while on some vehicles.
What do the failure codes mean? When the test was conducted, the temporarily sealed system would not hold vacuum/pressure so something is leaking: hose, valve, cannister, tank, gas cap. The leak is usually described as either large or small to aid in the diagnostics.
Now what does all of this mean for you? Usually an evap code says that the vehicle has failed the system integrity test which means that you are polluting the atmosphere with gas fumes and/or you cant easily fill the gas tank. Usually this has zero effect on engine performance because that entire system is isolated from the engine by the purge solenoid valve which is normally closed. The exception to this would be a purge valve that is stuck open, is erroneously being commended open or is leaking at the engine intake. This would manifest as a standard issue vacuum leak and can be proven as such. Let me know if you need help diagnosing any of this.
George
Hi. Thanks for the thrtough reply. I'm starting to understand this. What I was curious about was WHAT exactly was that vaccume line that I plugged back into the rubber hose for as it seems to the off into the engine somewhere through another line and what is is supposed to be sucking air for.
After running a code reader on it again after reconnecting this I do no have the p0440 code anymore which I have heard means (big leak) whereas p0442 means (small leak). The only code I have now (though it says 2 of 2 - they are the same) is p0452 which apparently has to do with the fuel pressure sensor on the tank.
Either your fuel tank pressure sensor, its connector, or wiring has failed or you still have a leak, blockage or faulty solenoid in the evap system. I would start with testing your engine vacuum.
12-01-2012, 09:59 PM
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