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ok after i did tons of work on this truck i have not yet got any codes but when i ran a scan i get evap purge leak fail, so i expect soon i will be getting another ecu code and most likely p0442 . anyway is this failed test telling me i have a possible purge valve? i put on a new one last spring along with a new vent, the vent seems to be passing, but i see the fail for the purge. so outside of the test port that may be leaking is this fail pointing me to the purge valve? or could it be the line running over the trans and back along the frame. i have new line from the filter back the all the rest of the system the only old part is the line over the trans. if i do get the p0442 i will just take all of this off and bench test it but getting a bit of insight will help to point me for sure in that direction. thanks
post the year and engine size or i may pull up the wrong diagnostic.
p0442 is a evap small leak dtc. the ecm seals the evap system and monitors the fuel tank pressure sensor. If it doesn't register a calibrated pressure change...it thinks a leak is present.
What are you seeing that indicates a purge fail? purge during non purge condition is a different dtc. to leak check the purge...start the engine...disconnect the purge vac line out to the cannister and electical connetor. if you feel vacuum at the purge...replace it. this will cause both evap leak and purge fail dtc.
ok thanks 2000 2.2L auto i ran a scan with the harbor freight scanner and it had 2 incomplete tests on the evap I M readiness tests. last spring i had the p0440 code and after changing the vent and purge valves i still had it and then found the filler neck had a million pin holes in it that i did not see when i had the part out doing the first smoker tests. i changed that and i tested it with putting 1/2 psi on the filler with the cap on and it held pressure for hours and i stopped the test. my smoker has a flow meter and that meter did not flutter so it tells me that was sealed.
i also did the same test at the split i have in the purge line at the fuel filter. i split the line there when i had every thing out of the truck to replace the lines and pump
i did test the purge valve from the TB port with a vacuum pump and pulled it to 15" of vacuum and it held for 4 hours so i stopped. maybe i should have also plugged the line at that split and pulled a vacuum at the test port to see if the purge was holding on that side of the valve, that may tell me the valve is either not holding or that i may have a leak in the line or o rings at the valve or going back over the transmission.
if the code comes back i will do that and see if i have a leak with the smoker and monitor that flow meter for a flutter and the pressure gage with the air from the tank turned off and see if the pressure drops or the flow gage has any flutter on the ball.
the flow meter should drop to zero...this indicates no leaks. It will take a few minutes to fill the system. Any flow, regardless of flutter is a leak. testing limits allow 0.010" leak decay to pass. The newer vehicles i work on; after repair will show zero flow after filling.
i would connect at the evap service port to conduct leak testing. (I don't want to move the fuel cap at this point...as it may be the problem. Some makes will not seal if you pressurize at the cap.)
If the flow meter drops to zero, you need to look at the pressure sensor or insufficient vacuum to the sensor.
if there is flow...i divide the system in half as an easy connection point....flow test the front; if its good the leak is in the back...you have eliminated half the system. Work your way back until the flow is zero.
the flow meter should drop to zero...this indicates no leaks. It will take a few minutes to fill the system. Any flow, regardless of flutter is a leak. testing limits allow 0.010" leak decay to pass. The newer vehicles i work on; after repair will show zero flow after filling.
( ( yes i split the system and put the smoker with the flow meter in the back section. i split the smoker about where the fuel filter is located. i powered the vent valve with a small battery and left the gas cap in place ( i tested the filler neck with the cap in place before this test ). the smoker has a flow meter on it and the flow meter puts out 1/2 psi and i have an input psi gage rateed at 60 psa so when i put air on the smoker i turn down the air compressor output pressure. and on the back half of the system when i had the smoker connected the flow meter stopped fluttering and the ball just sat on the bottom and i let it set for 4 hours and the pressure gage on the smoke held 15psi on the high side of the smoker))
i would connect at the evap service port to conduct leak testing. (I don't want to move the fuel cap at this point...as it may be the problem. Some makes will not seal if you pressurize at the cap.) ( if the code returns i will split the system again and then test the front half at the test port and see if it holds pressure and the flow meter stops fluttering and the ball sets on the bottom as you say. )
If the flow meter drops to zero, you need to look at the pressure sensor or insufficient vacuum to the sensor.
( the sensor does show that it is seeing a pressure change i looked at the sensor and when i put a bit of pressure on the filler neck the sensor changed )
if there is flow...i divide the system in half as an easy connection point....flow test the front; if its good the leak is in the back...you have eliminated half the system. Work your way back until the flow is zero.
thanks i expect the code to return soon as i do not drive the truck much and when it does i will take the purge valve out and bench test it with a vacuum, if it passes i will split the system and then go to the test port and sets with the smoker to see if it holds pressure and the flow meter ball stays on the bottom and no fluttering i will turn off the inlet pressure and let it set for 4 hours and see if the pressure gage drops, if it does them i have a leak in the lines, if i find a leak then new lines from the purge valve to the split will be in order.
thanks
February 3rd, 2023, 7:41 AM
evap purge leak fail
