2000 GMC SIERRA EMISSIONS FAILED

MY "SERVICE ENGINE SOON" LIGHT HAS BEEN ON FOR AROUND THREE YEARS (TAPED A ST. ANTHONY MEDAL OVER IT) AND TRUCK HAS BEEN RUNNING PERFECT. THREE YEARS AGO I DID HAVE TEST RUN AND MECHANIC SAID SOMETHING WITH
THE GAS CAP, HOWEVER, HE COULD NOT GET THE LIGHT TO GO OFF. FAST FORWARD, FLUNKED TEST BECAUSE OF CODES "PO440, EVAPORATIVE EMISSION SYSTEM" AND "PO449, EVAPORATIVE EMISSION SYSTEM VENT VALVE/SOLENOID CIRCUIT". BOUGHT GAS CAP, REPLACED VALVE CIRCUIT, THE LIGHT REFUSED TO GO OFF. THREE DIFFERENT PLACES TRIED TO USE THE LITTLE PLUG IN THINGS BUT THEY WOULD NOT TURN ON TO RESET COMPUTER. I WENT BACK TO EMISSIONS PLACE AND THEY REDID TEST SAME CODES, THEY SAID TO GO TO DEALER AND HAVE THEM RESET CODES, DEALER SAID THAT THE TRUCK DOES IT WITHIN 100 MILES AND TRUCK LIGHT WILL GO OFF. DROVE OVER 100MILES AND LIGHT STILL ON, I HAVE TO TAKE BACK TO MECHANIC WHO RAN OUT OF TIME AFTER TWO HOURS OF CHECKING FUSES AND STUFF. ANY HELP PLEASE, SINCE MECHANIC CHARGES BY THE HOUR..
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Let me guess...every time you fill the fuel tank, you try and get every last drop you can in the vehicle...after the gas hose stops, you slowly add as much as you can until it's at the top of the filler tank.
You aren't the only person that does this...but it causes raw gas to get into your evaporative cannister where only fumes are supposed to go. Gasoline in the emission can screws up the system.
Secondly, please don't use all caps when you type...It's irritating to read.
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Wow! You know me! Sorry about all caps but I really wanted to be noticed. I now wish I would have made a point to drive by the emissions checker like I did in the past three yearsw (light has been on that long) to renew my plates because I really think my problem is that the light won't shut off. As far as gas in the evaparative cannister when they changed that part (they did this) they should have been able to reset the light but could not. They wanted me to ask emission place to hook up the tail pipe but they said dept of natural resourses does not allow on a 2000. I have already been issued a ticket for expired plates and can't afford another. Help Advocate wrote:

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There is a leak somewhere in the evap system that has to be traced down, modern technology now uses a smoke machine to check all the evap components for leaks or non operating valves/solenoids, only way to fix the problem , resetting the pcm accomplishes nothing.

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Thanks so much, Would you have spent 2 hours checking fuses, replacing that part and trying tor reset because this mechanic charges by the hour. Is ninety dollars an hour the going rate? I don't have alot of money and wondering how much this could cost. Thanks for replying. Have you heard of this problem in a 2000 truck, I do make sure I turn the truck off when I fill and put the cap on tight. Shep wrote:

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The going rate is high for upstate NY, but the rate means nothing if the shop doesn't have the equipment and backround to fix this.

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To check for EVAP leaks there will be a light green colored cap with hoses connecting up to it, they are typically no larger than quarter inch in size and some vehicles will have multiple test ports of this type. This is the location or connecting port if you will where smoke/vapor and or vacuum is applied to the EVAP system, if a leak is suspected via code on the diagnostic computer then in some cases low vacuum is applied and has to maintain a certain level for a period of time. If a leak is detected then a tool that generates smoke/vapor "NON FLAMBLE" is pumped in at low pressure and you will quickly find the leak,some shops just jump right to this step and skip the vacuum, its well worth the shop charge since most mechanics using the tools of this type and training ASE certified should find and fix the leak within an hour or so plus parts....hehe. A competent NEW car dealership shop should have this equipment on hand since it is a common problem now a days. And if it cant be fixed just shoot it! :-)
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