1. Attachments are working again! Check out this thread for more details and to report any other bugs.

Dancing Fuel Pips + Gas Sensor Issue?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Hybrid Hobo, Jun 25, 2024.

  1. Hybrid Hobo

    Hybrid Hobo Member

    Joined:
    Jun 5, 2018
    165
    44
    0
    Location:
    New Jersey
    Vehicle:
    2008 Prius
    Model:
    N/A
    As some of you may recall - because I posted my experience here - I had my instrument cluster repaired about 15 months ago.

    It's working fine, but I notice that the little pips that represent the amount of fuel on the instrument panel having been dancing around again (going up & down) over the past week or so. This in and of itself (while a pain in the nice person) isn't cause for alarm, but I'm not sure if it ties in with something VERY odd that happened this morning.

    Since the pips have been dancing around lately, I'm never really sure exactly how much gas I have at any given point. And this is on top of the already inaccurate "guess gauges" on Prius'! So...

    I always make it a habit of refueling when the pips are at 3 to be on the safe side. I had about 4 or 5 when I went to bed in the car last night, and when I awoke this morning and started driving the last pip was blinking!!!

    Fortunately, I was right near a gas station, but this is where it gets even stranger...

    Like clockwork, every time I fill up, the car only takes between 3.5 to 4.5 gallons...and again, that's usually on 3 pips. Since the light was blinking and the tank was probably empty today, I figured it would need a good 5-6 gallons. Well...

    The pump clicked off at about the usual place, 3.5 gallons or so. But I figured that can't be accurate as the tank was basically empty, and I proceeded to keep filling it.

    The pump never clicked off again, and after about 6.2 gallons I decided to remove the nozzle. About 3 seconds after I did, fuel started gushing out from the tank. About a half gallon or so worth.

    Aside from being very embarrassed at that moment, I'm left with a few perplexing questions that maybe you guys know the answers to...

    *Why didn't the pump click off after the first time when I decided to keep filling it? Could it be an issue with the tank sensor?

    *Since I know the bladder can expand in warmer weather (it's been 90+ here) and the tank was empty, how can 6 gallons be too much when I believe it can hold 11 or 12 (if I remember correctly)?

    *Did I do any damage to the car by overfilling it? I drove it a few miles to work afterwards with no problem, but just wanting reassurance.

    P.S. - I realize that some of these might be dumb questions, but I'm the type of person who analyzes everything, and tries to prevent problems from occurring before they happen, or get worse.

    Thanks
     
  2. Tombukt2

    Tombukt2 Senior Member

    Joined:
    Nov 29, 2020
    9,119
    1,580
    0
    Location:
    Durham NC
    Vehicle:
    2009 Prius
    Model:
    Base
    I overfill all four of mine all the time in an attempt to stretch the bladder in the tank that similar to a well pump blue tank. A gallon didn't come out of the car when it burped It looks a lot but it is not I doubt if it's even a quart I've learned how to fill the car up to the first stop and then I slowly feel it until it burps like you're talking about but just as it starts to make the noise that it's going to burp I make sure I lift the fuel nozzle up to within 10 mm of the rubber trimmed hole that it's stuck into in the car and then usually it won't burp it'll run up to the tip of the nozzle and I'm holding the nozzle hard to one side of that rubber that's in the hole and it makes more airspace and it will suck in air rather than pull or push the fuel towards the nozzle trying to activate the shut off and then pushing it down the side of the quarter panel onto the tire and on the ground. There's not much fuel coming out I promise you If you could rig up a pan to set your rear tire in while you're pumping gas you would see It's almost nothing. I have driven these cars without gas gauges for close to a year at a time generally my methodology is to fill the car till it burps and I'm stretching the bladder and then I drive about 410 mi and I'm getting fuel and once I do that once and I see how much I put in that's going to be pretty much consistent because I drive the car about the same all the time under the same conditions air conditioning so on and so forth. So generally what it works out to be for me even if the gas gauge somewhat works I fill it up with around 8.4 to 9.0 gallons it burps cap it off I drive about 400 mi to 410 maybe 4:20 The pip has been flashing for about 15 mi I pull into sheets gas up with the blue fuel and I put about 9 gallons in and do it all over again so I tend to use my trip meter or my watch . I've never run out of gas. I run the car out of gas intentionally the minute I get it I fill it up and run it out till it dies then I dump 2 gallons in and go to the gas station so I know where my pips are sitting and what everything looks like in about what the mileage is running it out of fuel I have to know this. I doubt you done any damage You might be wanting to search for a gas tank out of a lower mileage similar car I'm always wondering if a Yaris tank could be fitted in the UK they don't have the bladder in the tank so you can change the fuel pump and change the sending unit in the US federal spec this cannot be accomplished You need $1,000 gas tank. Oh and good luck buddy
     
    Hybrid Hobo likes this.
  3. Hybrid Hobo

    Hybrid Hobo Member

    Joined:
    Jun 5, 2018
    165
    44
    0
    Location:
    New Jersey
    Vehicle:
    2008 Prius
    Model:
    N/A
    Great info, thanks!
     
  4. ChapmanF

    ChapmanF Senior Member

    Joined:
    Mar 30, 2008
    23,995
    15,589
    0
    Location:
    Indiana, USA
    Vehicle:
    2010 Prius
    Model:
    IV
    Taking these a little out of order...

    This question assumes the tank was empty. But another possibility is something is flaky in the gauge reading and the tank might not have been empty. There are other parts of your story that make that seem like it could be a live possibility.

    The filling-and-clicking-off behavior depends on the whole onboard-refueling-vapor-recovery system, which is more complex than just a single sensor. In fact, the level sensor is really kind of unrelated to the whole ORVR business (except in the indirect way that it might lead you to overfill if it showed you the tank was less full than it was).

    [​IMG]

    Each time the tank is overfilled carries a risk of leaving the ORVR system b0rked, but it doesn't happen every time; some people have long lucky streaks. When it's b0rked it'll be hard to fill pretty much every time, take only small amounts of fuel, or slosh them back out at you.

    So just pay attention the next few times you fill; if it doesn't do those things, you escaped angering the ORVR god this time, go and sin no more.

    We had one thread a while back where somebody with an overfilling habit complained about the only-small-fills, sloshing-back problem, got the ORVR system fixed, was advised to lose the overfilling habit, but managed eight months of no problems before posting a nearly-identical thread again.

    If your fuel gauge reading isn't dependable, I'd start by trying to figure out if that's an issue in the wiring back to the tank (probably easy to fix) or the level sensor inside the tank itself. I don't think you can change the level sensor in the gen 2 bladder tank, short of just swapping the tank.
     
  5. Tombukt2

    Tombukt2 Senior Member

    Joined:
    Nov 29, 2020
    9,119
    1,580
    0
    Location:
    Durham NC
    Vehicle:
    2009 Prius
    Model:
    Base
    I've been overfilling with the '09 work vehicle for years in hopes that this QR ORVR whatever we're talking about here would go bad so I could rip it apart and see what I need to do to it but that's not happened at least not that I know of when the flashing light or pip is flashing and I pull into a gas station I can fill on high speed all the way up to 8.4 gallons is where it'll click off like clockwork no matter where in the world I'm getting the gas then I manually pull the silver tube of the filler until it is about 10 mm in the hole touching the rubber grommet that lines the hole of the filler neck then I hold it tight to one side so air can get past a little bit and then I squeeze the handle almost halfway and I'll be able to run it up to about 10 gallons and then I'll hear the gas coming up the filler neck and I know it's going to belch so I stop I listen for a second I can hear everything rising and belching but not on me it's happening in the neck then I had two more squirts and I see the fuel settle just past the filler neck hole and I'm staring at the gas that is now all the way up to the top of the filler neck like it's not supposed to be I put the cap on and I'm driving immediately My gas gauge within seconds has gone to full and I'm already showing 36 miles per gallon on the MFD and have not even gone to miles and it'll be 43 in the next two or three miles. So I have not broke it enough to tear it apart. And then I'm wondering if a Yaris tank can be made to work something similar to that should be almost a direct swap it looks like.