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Can't fill tank, usual fixes didn't work!

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by exposure_therapy, Oct 22, 2014.

  1. exposure_therapy

    exposure_therapy Junior Member

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    I was wondering if anyone with more mechanical/Prius knowledge could help me troubleshoot what’s wrong with my car. It’s a 2006 Prius, with about 66,000 miles on it. In the past 8 years, I’ve never had any problems with it – but for the past two months, I’m been having two separate (but related) problems, described below. I've searched google and this subreddit extensively, and can see that similar questions pop up often - but so far, none of the usual fixes have worked!

    1. No matter how much gas the car needs, when I try to refuel, the pump shuts off automatically after about 4 gallons. When I try to add more gas, the auto-shutoff is triggered immediately – so to fill the tank, I have to stand there “pumping” the lever over and over and over for about 10 minutes, as I fill the tank .02 gallons at a time. (To answer a question Toyota asked - this happens at all gas stations, and I’ve had multiple other people try pumping my gas for me, so I know it’s not user error.)

    2. The fuel gauge is no longer accurate. For the past 8 years, the bars on the digital fuel gauge (which each represent about 1.2 gallons) have gone down about every 50 miles or so. Now, the first bar takes forever to go away, and the other bars go down at random intervals. The last time I filled up, the gauge still read “full” even though I had driven for 165 miles. The rest of the bars go down at random intervals – sometimes after 10 miles, sometimes after 30, 40, or 60ish miles. There’s no pattern to this (I’ve been keeping track for the past 4 fill-ups, and it’s been different every time).
    Both of these problems happened for the first time after I tried to "top off" the tank before a big trip. I had driven less than 100 miles since my last fill up, and still had 8/10 bars on the fuel gauge. I added about 2-3 gallons of gas, and noticed that the fuel gauge didn't go back to "full" when I turned the car back on. However, it went up after about 5 minutes. The above problems occurred the very next time I filled up (at the end of a long drive, when the car needed about 7-8 gallons), and have happened ever since (over the course of 2 months, and about 3,000 miles). I've read about the 2nd problem (with the fuel gauge) happening with other cars after topping-off, but from everything I've read online, it sounds like simply recalibrating the fuel sensor/gauge would have fixed this (it hasn't).

    Luckily the car’s computer displays my MPG – and this calculation is based on the miles driven, and the gas actually flowing through the fuel injector, so it’s completely accurate. When I need to get gas, I look at the MPG, and divide it by the number of miles driven, to find out exactly how much gas I’ve used. I then stand at the pump and force the exact amount of gas needed into the tank, as described in #1 above. (Thanks to this method, I've never run out of gas - but this problem is incredibly annoying, and means that every trip to the gas station takes about 15 minutes.)

    So far, Toyota is stumped. When I first brought the car in, they ran a diagnostic, and gave me a new fuel neck filler valve (from my own reading, I can see that the 2004 Prius was having the gas-pump-auto-shutoff problem, and this was the official fix from Toyota… so they must have assumed my car was doing the same thing). However, this didn’t fix either problem. They then took the entire fuel system apart, inspected it, put it back together, and gave me a new gas cap (because mine was “breathing a little funny”). This resulted in me successfully filling the tank once and then the problem came back.

    Next, they took out the fuel canister, ran it through some tests, and said it was working perfectly normally. Then, they took out my entire gas tank, and replaced it with a gas tank from another Prius. However, this still didn’t fix the problem – so the problem doesn’t seem to be with the tank itself or with the internal bladder. Throughout all of this, I’ve also recalibrated the fuel gauge myself using these instructions, but that doesn’t help either.

    In summary, we’ve already ruled out the following:

    1. Recalibrating the fuel gauge

    2. Fuel neck filler valve

    3. Gas cap

    4. Gas tank and bladder

    5. Fuel canister (haven’t tried replacing it, but they took it out and examined it, and it "performs normally in testing")

    6. User error
    Problem #1 temporarily went away for one fill-up, right after the mechanics took everything apart and put it back together - and then the problem started happening again.

    Any other ideas? Over the past two months, I’ve wasted an incredible amount of time and energy trying to get this fixed!
     
  2. SageBrush

    SageBrush Senior Member

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    Unique story, you have. Sorry!

    Please clarify this point though: if your tank has a few gallons in it after you drive around for a few days, can you then put in 4 gallons before the problem recurs ?
     
  3. exposure_therapy

    exposure_therapy Junior Member

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    I haven't done extensive testing on that - I usually keep forcing fuel in so that I know the tank is full, because filling all the way up and monitoring my MPG is currently the only way of keeping track of how much fuel is left. However, the first few times it happened, I left the gas station after only 4 gallons went it, and then drove to a different gas station later in the day, and got about 2 more gallons in. So it seems like whenever I buy gas, I get a short amount of time where fuel goes in normally, and then the auto shut-offs begin (usually after about 4 gallons have gone in).
     
  4. SageBrush

    SageBrush Senior Member

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    I don't know why the problem is happening, but in your shoes I would be much happier just putting in 4 gallons at a time rather than trying to fill the tank over 15 minutes. Reset a trip meter and know that you have at least 200 miles until the next station visit.

    I have experienced something similar with our Gen2 Prius: a couple gallons would go in, and then the nozzle would auto-stop. I knew the tank had a lot of empty space so I would start pumping, only to have the nozzle auto-stop after a second or three. This behavior was reproducible. Usually I could correct the problem by just letting the nozzle sit in the tank filler neck for 10 - 15 seconds and not using the high pressure flow setting. I'll guess I saw this problem perhaps once a year, typically in cold weather. PriusChat always explained the problem as an idiosyncrasy of the tank bladder, but I do not understand the tank construction well enough to really follow. I always imagined that the tank needed 'burbing' ;)
     
  5. exposure_therapy

    exposure_therapy Junior Member

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    The "4 gallons" thing is just an estimate, though - sometimes it *does* just stop after one gallon!

    I've read a lot about the bladder problem, which seems to be common. However, we've already ruled out the bladder, since the mechanic replaced the entire tank/bladder assembly for me about 2 weeks ago - which didn't help at all. Luckily I wasn't charged for it - he just swapped it out from one of the dealership's cars so we could test it (and he'll put the old tank back in the next time I bring it in).
     
  6. SageBrush

    SageBrush Senior Member

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    I propose an experiment, that may also provide you a work-around if so inclined:
    Fill a 5 gallon petrol container, and use that to fill the car (slowly the first time, of course, to avoid spills.)

    You should then know if the car fuel assembly is just triggering the nozzle for the fun of it, or if fuel really is rising high enough to 'appropriately' stop flow.
     
    #6 SageBrush, Oct 22, 2014
    Last edited: Oct 22, 2014
  7. exstudent

    exstudent Senior Member

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    Topping off the tank is most likely the root cause of everything. I would put money that a valve/s is/are stuck in the wrong position (open or closed), and/or, the charcoal canister is obstructed. As you noted, the various gas station pumps are correctly triggering off b/c the build-up of air pressure inside the gas tank (aka bladder) is not correctly going into the fuel EVAP system, allowing for a normal fill-up.

    See attached PDF.

    1) Did the new fuel neck filler valve also include a NEW Refuel Check Valve and NEW Fuel Cut-Off Valve? See fig 3.9 and 3.10; two different valves on this upper fuel filler pipe.
    2) Did they check the other valves and the charcoal canister on your tank? See fig 3.12
    • Fresh Air Valve
    • Canister Closed Valve [AKA: Can Ctrl Vsv (CCV VSV)]
    • Purge Flow Switching Valve (AKA Tank bypass VSV)
    • Charcoal Canister
    Good luck. Report back with the final solution.
     

    Attached Files:

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  8. JC91006

    JC91006 Senior Member

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    1. How low do you let the fuel gauge go before you refill?
    2. How many miles do you normally drive before refueling?
    3. How many gas stations have you tried?
    4. Do you fill up while holding the fuel trigger or let it fill automatically without holding the nozzle?
    5. How far do you push the nozzle into the filler neck?
     
  9. exposure_therapy

    exposure_therapy Junior Member

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    1. Between 1/4 - 1/2 tank left (around 3 or 4 bars remaining)

    2. 300ish

    3. Maybe 10? I'm living out of state for work at the moment, so I drive about 500 miles each weekend so I can spend time with my family. I've tried a LOT of gas stations, in different states!

    4. Before this problem started, I used to let it go automatically (assuming I was at a gas station that had the little tab on the trigger to let me do this). Now, if I'm at a gas station like that, I can let it go automatically for the first 1-4 gallons, and then it shuts off. Then I I have to stand there and hold the trigger down myself (pulling it over and over and over) in order to get any gas in.

    5. I've always put the nozzle in as far as it needs to go for the rubber part to get a good seal. However, since this has been happening, I've tried readjusting it -pulling it further out, pushing it further in, jiggling it around. Nothing makes a difference.

    Thanks! Before trying this myself, I'll have to ask the mechanic if he's done it yet. (Since he already took the entire fuel assembly apart, and swapped my tank for another one, I'm wondering if they had to use a fuel canister to transfer the gas.)

    I'm not sure, but I'll find out. Thank you for the suggestion!
     
    #9 exposure_therapy, Oct 23, 2014
    Last edited by a moderator: Oct 23, 2014
  10. usnavystgc

    usnavystgc Die Hard DIYer and Ebike enthusiast.

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    If I were in your shoes, here's what I would try. I would "fill up" until the pump shuts off automatically. Turn it off and begin to drive. I would drive for at least 400 miles but, I would try to take it to 500 if I could. I would likely carry a 5 gallon gas can with me just in case. There should be at least ten gallons in your tank regardless of variations in the bladder. The Prius is finicky and over time errors in the gas guage add up and the next thing you know, its all out of whack. This is corrected by starting from a baseline (as close to zero as possible). I do believe you have been overfilling your tank everytime. I'm betting you could go nearly 600 miles on an overfilled tank but that's a different story for a different day.

    I want you to know that many will refute the advice I'm giving you. I can hear it now, "Don't take a chance on running the car out of Gas", "its not good for the fuel pump to go below two gallons" etc., etc.. All I can say is "try it, you might like it". As I stated above, this is what I would do and have done (although my car has never been as chaotic as yours).
     
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  11. SageBrush

    SageBrush Senior Member

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    ^^
    OP has been easily filling his tank with 1 - 4 gallons, and then spending another 10 - 15 minutes to get a 'full tank' in. So the presumption is that the tank has room for 8 - 10 gallons when he pulls into the station; the difficulty is getting that volume in.
     
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  12. usnavystgc

    usnavystgc Die Hard DIYer and Ebike enthusiast.

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    I hear you Sage, What's happening is he is consistently overfilling it. I'm betting he's forcing at least 11-12 gallons in there. This makes the gauge not know what to do and very inaccurate (just as he describes). Also, the gauge likes to measure large changes and it is much more accurate when it does. A constant input of 4 gallons exacerbates the problem. The Gen II needs greater than 3 gallons to even register a change in volume on the guage (this is why I say carry a 5 gal can of gas). The only real way (I know of ) to fix this problem is to run it nearly out of gas (at least 400 miles or about 8 gals (500+ is better)).

    If you run 500 miles at 45 mpg, that will be about 11 gallons. If your not getting 45mpg, go lower on the miles. The true test will be after he runs 400+ miles and goes to fill up. Where will the pump shut off then. I'm betting it will be at least 8 gallons and if he takes it to 500 miles, I'm betting at least ten. There is only one way to find out and that's to do it.
     
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  13. JC91006

    JC91006 Senior Member

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    I believe you are filling up the tank a little too soon. Depending on your type of driving, 300ish miles could be 6 gallons of fuel or maybe slightly less if you get close to 60mpg. If you are filling up at that point, with the bladder of the GenII cars, there's a very good possibility you would only get 4.xx gallons in before the pump stops. I often fill up with the tank 1 or 2 bars under half on my 2006 car and many times get the amount you are describing, 4.xx gallons. The tank is not full at this point and it would only take 200-250 miles before the fuel gauge goes back down to that level of where I filled up, 1 or 2 bars under halfway.

    I also feel you are putting the nozzle too far into the fuel neck. You simple have to gently put in the nozzle and push downward to "lock" it in place while you are filling. Do not shove the nozzle all the way in, it would prevent the car from filling up properly.

    As an experiment, try to let your car go all the way to 1 bar or to the blinking 1 bar where the car comes out with the message "add fuel" and beeps at you. At this stage you should still have 2 gallons remaining in your gas tank so you are nowhere near empty. This should allow you to get at least 80-100 miles before the car runs out of gas.

    Try filling up at this point and see if you can get 8-9 gallons in on the first try. I think you'll be pleasantly surprise at the results if you try this.
     
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  14. wjtracy

    wjtracy Senior Member

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    Lesson is the original topping off was not a good idea.

    >> CAUTION DON'T TRY THIS WITHOUT SOME CAREFUL THOUGHT but here is a possible work-around: According to John (BritPrius), I think he recently told me here, he gets his tank to fill up completely by pumping with the nozzle up-side down.

    But this gets into the question I asked him: in general, on a Gen2, why does the gaso pump stop pumping? Is it pressure or liquid level or what? I can *never* get more than 8 gals in there...well actually sometimes it goes to 9-gals and then I finally have a chance at 450 miles cruising range on a tank. A few months ago I got a good full fill-up and it was only 70F outside.

    So I have been experimenting, but seems like when you stick the nozzle in there, there is no way to have vapor escape. When mine is "full" (actually not full, but not taking any more) I can't get more in.
     
  15. JC91006

    JC91006 Senior Member

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    Just for kicks, I just went to fill up my tank earlier than usual. My gauge is at the halfway mark, mileage wise, I've gone 223 miles and my car consistently averages 47 mpg. I was able to put in only 3.56 gallons before the pump stopped. My fuel gauge showed full after the fillup of only 3.56 gallons.

    I don't believe the fuel tank is full. It's caused by the bladder in the tank giving the false sense of "full". So if my theory is correct, in 167 miles, my fuel gauge will read at the half full mark, where I started when I filled up with 3.56 gallons.
     
  16. SageBrush

    SageBrush Senior Member

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    Howstuffworks has a nice explanation of how a fuel nozzle knows when to auto shut off. The trick is ingenious, but it boils down to having a functional pressure gauge at the tip of the nozzle.
     
    #16 SageBrush, Oct 23, 2014
    Last edited: Oct 23, 2014
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  17. wjtracy

    wjtracy Senior Member

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    ...I knew about the Olean, NY invention of the gaso shut-off valve since my mother is from there...
     
  18. Fred_H

    Fred_H Misoversimplifier

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    I agree those are the most likely causes.

    It looks like the "Fresh Air Valve" and the "Canister Closed Valve" along with the attatched "Trap Filter" and possibly also the "Fresh Air Line" all need to be fully open and unobstructed during refueling. Otherwise the air in the space between the metal tank and the bladder could not escape quickly enough, and the bladder could not expand quickly enough. An obstruction or stuck valve would likely cause exactly the symptoms that exposure_therapy described.

    A simple test might be to disconnect the "Trap Filter" from the tank during refueling, and see if that helps. Or disconnect the "Trap Filter" from the tank and blow air through it and the following valves to check for obstruction.
     
  19. 69shovlhed

    69shovlhed Surly tree hugger

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    I'd keep a full 5 gal can in the car just in case, and run it down till it says add fuel and the pip flashes instead of filling early. also, I usually only put the handle clip on the second notch when I fill up, but since its a small tank it doesn't take that long anyway. if it still won't fill, turn the nozzle upside down and see if it helps.
    and someone did say that if you disconnect the 12v battery for 10 minutes it will reset the fuel gauge. I don't know if that's true though.
     
  20. exposure_therapy

    exposure_therapy Junior Member

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    Thank you everyone, for the advice! I now have an official "engineering ticket" open at Toyota, so it's not just the one individual mechanic working on it anymore - and after reviewing all of the information, the engineers have agreed that there's something very wrong, and this is far beyond the usual problems with the bladder or with overfilling. Toyota is now working with the dealership mechanic, to tell him which parts to test next.

    I'm going to bring it in on Tuesday, and they're going to try giving me a new "fuel neck filler assembly" (before, they had only replaced the fuel neck filler valve). I think this should include many of the valves that exstudent suggested. In addition, I mentioned to the mechanic that I had posted here, and he asked me to bring in a list of everyone's suggestions.

    To address a few of the suggestions directly:

    I'm not overfilling it. I've owned the car for 8 years, always fill the tank completely, and have actually kept a record of every fuel purchase I've ever made over at fueleconomy.gov (I'm a huge nerd) - so from the very first time this happened, I knew exactly how far I had driven since my last fill, and exactly how much gas was needed to fill the tank. From looking back on this data, I have concrete evidence that the car has been behaving very differently in the past 2 months, as compared to the previous 8 years.

    For the life of the car, I've always driven about 300-400 miles before buying gas. At that point, there are typically 2 or 3 bars left on the fuel gauge, and the pump automatically shuts off after I add 7 or 8 gallons. I've *never* try to "top it off" to get the fuel to come to an even price or anything like that - I've only put in exactly what was required to get the pump to shut off. When I said that I "topped it off" before all of this started happening, I meant that I had only driven about 100-150 miles since my last fill-up, and added an additional 2 gallons of gas before making a long drive. (That was the one and only time I've ever done that, and if there's even the slightest chance that that broke something, I really regret it!)

    I currently live 260 miles away from my fiance, and drive home to see him almost every weekend. The problem that I'm having is that I'm routinely driving over 400 miles at a time without filling up, and when I go to buy gas, the pump shuts off after only 4 gallons. If I stop filling then, and look at the fuel gauge, it says that the tank is only half full.

    Surely, my 2006 Prius is not suddenly getting over 100 miles per gallon!
    (especially when the computer, which gets its information from the fuel injector, is telling me that I'm getting 45mpg!) Based on the distance I had driven, it should take at least another 4 gallons at that point, no matter what!

    Finally, the mechanic has now completely disassembled and reassembled the fuel tank assembly several times. He's swapped out the fuel tank. He's drained the fuel tank, and re-filled it, and then re-calibrated the fuel sensor. I've left the dealership with a full tank of gas, knowing it's a full tank of gas, and with strict instructions not to fill up until I have only 2 bars of gas remaining. Under those conditions, after I've driven close to 500 miles, the car should be accepting more than 4 gallons of gas at a time!