2002 Blazer 4.3L (Code P0440)

My service engine soon light has been on for months now. I figure it is time to fix before emissions inspections come around. This code indicates a malfunction in the EVAP system I suspect that a leak
exists. Is the system pressurized? Should there be a hint of pressure when you release the gas cap? My does not seem to have any pressure when releasing ther cap as other cars do. I figure I could find this possible leak and fix it for less than a diagnosis alone. Has anybody had this experience and what did you do? Any help appreciated.
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I don't have the info in front of me at the moment. I would try a new gas cap, clear the code and see what happens.
James
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you can try the gas cap and you may be the one in ten that, from my exp., it works for. A few possibilities, leak in fuel feed or return lines, leak in EVAP celoniod or purge lines or tank(doubtful on an 02). Now for the real possibilities: 1) near tank celonoid(above rear diff.), 2)on engine-EVAP purge celonoid or lastly the pressure sensor on the top of the tank. I would myself-make sure the cap is tight and good. Secondly(personal opinion) buy GM replacement products. Thirdly(after making absolute sure the previously two suggestions didn't work)-I would go at the celonoid near the tank. Keep in mind without a scan tool or access to one, this 'test' for the EVAP system takes some time to run. GM does have a procedure(or I'm sure you can find it on line)to run this 'monitor'(test). Make sure you don't spend excess time and money until you're sire the test has run and failed. I've worked on hundreds of these and driven in some cases a hundred miles without test running-make sure before jumping to any conclusions that you know the test did or didn't run before moving ahead. This sometimes is a tough code to run down. But the time to start is soon if an inspection is coming up because it may take some time. good luck snipped-for-privacy@peru-motors.com
On Feb 18, 8:06 pm, snipped-for-privacy@gmail.com wrote:

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snipped-for-privacy@gmail.com wrote:

The system runs under NO pressure. The light is activated when the system detects that it cannot hold a VERY low vacuum. The system does the test when the fuel tank is between 15-80% full, The engine temperature is within a few degrees of the exterior temperature (cold engine)and under a set speed. It does the test by commanding the rear purge valve CLOSED and opening the front purge solenoid. It then measures the vacuum in the tank and times how long it takes for the vacuum to drop by a set amount. If it drops too fast it turns the light on.
Just repaired a P0440 code on the wifes 02 Blazer. The problem was the vapor canister purge valve.(which has been a COMMON problem) On vehicle testing is difficult without a smoke machine.
ACDELCO Part # 214633 - $12.25 from Rock Auto
There is also a purge solenoid located on the intake manifold. That item you can test with a hand vacuum pump. When it is disconnected it should be closed and should hold a vacuum on the side that runs to the tank.
ACDELCO Part # 214640 - $22.79 from Rock Auto
--
Steve W.

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