fuel tank EVAP lines

Discussion in 'Gen 2 Prius Technical Discussion' started by Dale I, Jul 22, 2025 at 11:59 PM.

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  1. Dale I

    Dale I Junior Member

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    I started pulling the fuel tank on my '07 today, to replace the charcoal canister. The two lines that have refused to budge are lines that need some kind of tool shoved into the joint to release them. I've got a set of Lisle line releasers but try as I might, the lines won't come off. Are there any videos showing how to separate those lines? line with tool loose.JPG line with tool loose.JPG
     
    #1 Dale I, Jul 22, 2025 at 11:59 PM
  2. Tombukt2

    Tombukt2 Senior Member

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    Push on square cutouts
     
    #2 Tombukt2, Jul 23, 2025 at 6:58 AM
  3. Tombukt2

    Tombukt2 Senior Member

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    Push on rectangular cut outs and pull apart like the one up front by brake actuator?
     
    #3 Tombukt2, Jul 23, 2025 at 6:59 AM
  4. Dale I

    Dale I Junior Member

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    The front fuel line has a side button to push but I didn't see such a design on the rear EVAP lines to the canister...I'll look again
     
    #4 Dale I, Jul 23, 2025 at 9:07 AM
  5. Tombukt2

    Tombukt2 Senior Member

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    Black things in your picture are the front ?
     
    #5 Tombukt2, Jul 23, 2025 at 10:39 AM
  6. Dale I

    Dale I Junior Member

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    The pic is of the rear of the car, behind the fuel tank. Line is from the charcoal canister.
     
    #6 Dale I, Jul 23, 2025 at 11:38 AM
  7. ebikeman

    ebikeman Junior Member

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    I need to replace mine. A mechanic friend jacked my car up, took off some kind of plastic inside my left rear fender area and we could see the canister right in front of us. I could reach out and touch it. He told me he could do the job without pulling the tank.

    How much effort was it to pull the tank? Did you have it up on a lift?

    Thank you,
    ebm
     
    #7 ebikeman, Jul 23, 2025 at 12:03 PM
  8. Dale I

    Dale I Junior Member

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    Charcoal canister is on top of the tank on the '07.
     
    #8 Dale I, Jul 23, 2025 at 1:50 PM
  9. Dale I

    Dale I Junior Member

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    I found the side buttons to release the lines...now the tank is hanging down...anyone who says that you don't have to pull the exhaust system to get the tank out....hasn't done the job, laying on their back with the rear tires on ramps...maybe its doable on a lift but it'll be a lot easier with the exhaust out of the way.
     
    #9 Dale I, Jul 23, 2025 at 3:06 PM
  10. Dale I

    Dale I Junior Member

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    Tank is out...and I had to drop the exhaust. Now it looks like the Vapor separator 77730-47030 is a more likely culprit for codes rather than the charcoal canister. Using a smoke generator into the tank, smoke comes out the intake pipe of the unit. I believe the valve is stuck open. Anyone ever pull one of these units and test it? gas tank top.JPG
     
    #10 Dale I, Jul 23, 2025 at 11:58 PM
  11. mr_guy_mann

    mr_guy_mann Senior Member

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    What codes do you have and what testing have you performed?

    That part # is for the "trap canister with outlet valve" - the valve is actually the leak detection pump assembly. The inlet "fitting" is the vent for the fuel tank - evap system and is normally supposed to be open.

    The pump "seals" the inlet when the ECM commands the vent solenoid shut and turns on the pump to check for leaks.

    The system leak test has two thresholds - a 0.040" leak and a 0.020" leak. My experience is that most smoke machines are marginally effective below around 0.025" leaks (ie, I can't see the smoke, but it leaks enough to set a P0456 small leak code). I often have to spray soapy water on components with the smoke machine pressurizing the system.

    Posted via the PriusChat mobile app.
     
    #11 mr_guy_mann, Jul 24, 2025 at 1:08 PM
  12. BiomedO1

    BiomedO1 Senior Member

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    Since you have it down and out; I probably just replace it - rather than test it. It could just be intermittent and works when dry. No gas clogging it when you overfill. As long as it doesn't cost an arm and a leg; weight against doing this job again if you get this failure again.... You got almost 20 years out of that old one.

    YMMV
     
    #12 BiomedO1, Jul 24, 2025 at 1:16 PM
  13. Dale I

    Dale I Junior Member

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    Here are smoke tests of the charcoal canister and the vapor separator. I don't know if these prove anything definitive but I'm most concerned with the vapor pump. Should smoke be going thru with no power connection? I did connect power, briefly, to the unit and it did sound like it was running the small pump. Vapor separator & smoke.JPG Charcoal canister & smoke.JPG
     
    #13 Dale I, Jul 24, 2025 at 1:36 PM
  14. Dale I

    Dale I Junior Member

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    The previous owner ran the car for over two years with EVAP codes. 441,446,455, I believe.
    I smoke tested the fuel filler cap and it held smoke. I replaced the separator valve at the canister with no change.
    At this point I have a new charcoal canister but don't want to re-install the tank if that testing pump is bad.
     
    #14 Dale I, Jul 24, 2025 at 4:22 PM
  15. BiomedO1

    BiomedO1 Senior Member

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    You need to find out if the valve is in the normally open or closed position, without power going to it. It's really a moot point, since you can't pass smog, register it, or buy insurance to legally run it on Ca roads.

    FWIW; the responsibility for the car passing smog is on the previous owner - unless you bought the car as a "parts car". Even on an as-is sales and private party in Ca - brakes and smog are expected to functioning properly. It's a public safety thing..... You should be able to find it in the Ca. vehicle codes....
     
    #15 BiomedO1, Jul 24, 2025 at 5:45 PM
  16. Dale I

    Dale I Junior Member

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    exactly what I trying to find out...normally open or normally closed, without power...yes, it will be a parts car if I can't get it to pass smog test...
     
    #16 Dale I, Jul 24, 2025 at 5:48 PM
  17. Brian1954

    Brian1954 Senior Member

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    This is answered in post #11.
     
    #17 Brian1954, Jul 24, 2025 at 9:59 PM
  18. Dale I

    Dale I Junior Member

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    OK, so it's a fact that the pump is "open" normally and waits for a signal to close....and what closes it to flow, is internal to the pump? So, I need to figure out which pins to activate to close it...or trust that it will work...and put the tank back in...
     
    #18 Dale I, Jul 24, 2025 at 11:57 PM
  19. mr_guy_mann

    mr_guy_mann Senior Member

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    IDK what tooling you have.

    When I see a car like this I first visually inspect the gas cap, then use a capable scantool to actuate all the solenoid valves via bidirectional commands. I want to see that the ECM "can" operate everything, and whether things move (make klunk sounds).

    Next perform the scantool evap system test and note the results. The Leak Detection Pump has a pump, solenoid valve, and a pressure sensor.

    When the solenoid is unpowered & "open", it vents the system, but at the same time it connects the pump and pressure sensor to a 0.020" orifice.

    The ECM turns on the pump and "calibrates" the test by seeing how much vacuum is possible with a known 0.020" leak. It then powers the solenoid on, which connects the evap system to the pump and pressure sensor.

    Now the pump is trying to apply vacuum to the entire tank and evap system. If there is no leak or it's smaller than 0.020", eventually the pump will achieve a "higher negative pressure" (more vacuum) than the calibration test value. The test passes.

    If it has a larger leak, it will never reach the calibration value and the test fails. The ECM looks at how badly it fails to decide if it's a small (P0456), medium (P0442), or gross (P0455) leak.

    Here's where I smoke the system, while everything is still together in the car. Sometimes I do have to drop the tank. Then I have to cap every line and smoke - soap test things.

    So yeah, I first want to "test the system", because pulling things down to test individual parts ain't no fun (and eats time).

    Posted via the PriusChat mobile app.
     
    #19 mr_guy_mann, Jul 25, 2025 at 8:24 AM
    BiomedO1 and Brian1954 like this.
  20. Dale I

    Dale I Junior Member

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    Thank you for a solid answer of steps to take.
    I started with a new gas cap and a used cap off of another Prius. Neither helped. I bought a smoke machine and tested the 3 caps in situ. The new cap was the worst! I couldn't get it to seal on my '07 or '04. One used cap would seal on the '07 and one on the '04 but I couldn't interchange them and have them seal...
    I pinched off the hose to the charcoal canister, btw. I also tried soapy water spray on everything I could see. This was after I pressure washed the entire area including the fuel filler piping. I had no bubbles or smoke come out of anything. I swapped out VSV valves between cars. No change. Only after all that did I drop the tank and bought a new charcoal canister, on the advice of a Toyota tech person who said that '07 cars had particularly frequent problems with bad canisters. When I pulled the tank, I pulled the vapor separator pump to examine it. I was looking for bits of charcoal, hoping that I'd find evidence of a bad canister. So far, I've found no bits in anything. I held a blank sheet of white paper in front of valves, pumps and lines as a blew air thru them. I assume that even though the pump spins and is open when no
    power is applied, it may not be closing when told to by the ECM. I am going to pull the fuel filler assembly and examine its various pieces for flaws. I've been told that often, the only way to get a gas cap to seal is to buy a new filler pipe as they get distorted by frequent over tightening and sloppy fuel filling techniques. I'd like to re-install the gas and expect different results...but I doubt it will happen...
     
    #20 Dale I, Jul 25, 2025 at 11:21 AM
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