Eric Sedletzky
Contributor
A while back @rsingler posted an article about the importance of meticulously repairing a reg that had IP problems and also O-ring related sealing problems.
My older Toyota Tacoma pickup that now has over 300k miles on it began developing evaporative emission problems, constantly causing the check engine light to go off and throwing an 0440 code (evap leak). Most of the time this is always a faulty gas cap. California compliant cars since the 90’s all have to have sealed gas tanks where no fumes can escape. Any fumes go into the intake manifold via a hose so fumes get burned up. If the computer senses a leak anywhere other than the evap hose it will set off the check engine light.
So I checked the gas cap and sure enough the sealing O-ring was cracked and worn. So I sourced another giant and thick O-ring that was about the right size and it worked…for a while.
Then the check engine light started going off again. Good thing I have my own diagnostic unit!
So I took off the gas cap and looked at everything very carefully. What I noticed was at the bottom edge of the gas filler pipe there were some deep scratches from the gas pump nozzle dragging across it for the last 20 years. So I took some 220 sand paper and sanded out the deep scratches then went up in grits finer until I ended up at 2000 grit. Probably overkill for a car fix but never the less the land where the O-ring sits is now flawless!
Next I checked the land on the gas cap itself and it was dirty but looked fine. So I cleaned it up.
I put a little silicone on the O-ring (which I looked over carefully too) and reinstalled it, tightened down the gas cap and cleared the code.
So far it’s held and after three tanks of gas, the check engine light has not gone off, so I guess I fixed it!
Thanks to @rsingler and his knowledge, it got me to think about how important O-rings are and especially the lands they rest on.
My older Toyota Tacoma pickup that now has over 300k miles on it began developing evaporative emission problems, constantly causing the check engine light to go off and throwing an 0440 code (evap leak). Most of the time this is always a faulty gas cap. California compliant cars since the 90’s all have to have sealed gas tanks where no fumes can escape. Any fumes go into the intake manifold via a hose so fumes get burned up. If the computer senses a leak anywhere other than the evap hose it will set off the check engine light.
So I checked the gas cap and sure enough the sealing O-ring was cracked and worn. So I sourced another giant and thick O-ring that was about the right size and it worked…for a while.
Then the check engine light started going off again. Good thing I have my own diagnostic unit!
So I took off the gas cap and looked at everything very carefully. What I noticed was at the bottom edge of the gas filler pipe there were some deep scratches from the gas pump nozzle dragging across it for the last 20 years. So I took some 220 sand paper and sanded out the deep scratches then went up in grits finer until I ended up at 2000 grit. Probably overkill for a car fix but never the less the land where the O-ring sits is now flawless!
Next I checked the land on the gas cap itself and it was dirty but looked fine. So I cleaned it up.
I put a little silicone on the O-ring (which I looked over carefully too) and reinstalled it, tightened down the gas cap and cleared the code.
So far it’s held and after three tanks of gas, the check engine light has not gone off, so I guess I fixed it!
Thanks to @rsingler and his knowledge, it got me to think about how important O-rings are and especially the lands they rest on.