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rpmdiag, Tech and Instructor
Category: Lexus
Satisfied Customers: 8144
Experience:  Since 1975
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I have a 99 RX300 which recently began giving me trouble

Customer Question

I have a 99 RX300 which recently began giving me trouble with filling the gas tank. It behaves as if the vent tube is not working, keeps backing up in filler tube, shutting off pump, taking 10-15 minutes to put 8-10 gallons in, then gas gauge proceeded to empty despite putting 8 gallons in. I disconnected the vent lines to the vapor apparatus and all seem patent. Next, I pulled the fuel pump and sending units from under rear seats, and when both passenger side and driver side floats are raised, the fuel gauge reads full as it should. I discovered that the passenger's side of the tank has no fuel in it, while the drivers side where the fuel pump was removed is full. I see in my service manual that there are fuel cut off valves at the top of the tank that connect to a fuel tank evaporation tube. Could one or both of these be the problem? I haven't tried blowing out the lines to the these valves, or any of the lines to the tank yet, and was hoping not to have to drop the tank. Will blowing the lines with compressed air cause any damage? Do you have any advice as to what the problem is, and what to do next?
Submitted: 1 year ago.
Category: Lexus
Expert:  rpmdiag replied 1 year ago.

Hi, I’m Ron and I can help you.
I have been in this business since 1975 and also teach automotive repair. I am confident we can resolve your problem together. Please understand that I don't know your skill level. I can't see, smell, hear, or touch the vehicle either, so it may take a few replies to get to satisfactory results. Please be patient!
I also try to give all of the information you may need, expecting a “positive rating” in return. I will also continue assisting you after you have rated me, if necessary. If there is any reason I cannot get a positive rating, please let me know why “in advance”, so I can go another direction for you. I am sorry you’re having this problem; I’ll help you through it.

Your vent valve is bad or plugged in your evap system

Thanks, Ron

Customer: replied 1 year ago.
My question was not whether there was a blocked vent line, it was whether or not blowing compressed air through the lines would be ok or whether it would cause a problem. I did not see the answer to this question, so I took a chance and blew the lines with compressed air. I heard a loud pop when blowing air into the plugged line from its attachment to the charcoal box, and the problem of filling the tank resolved, but now after driving for 100 miles the check engine light has come on with code P0441, and the car failed inspection. Can you advise me on what to do from here? Have I now damaged some type of valve?