Fuel gauge monitor

Pulin Jal - How long has this problem existed for you? Do you live in a cold winter season climate area? Since the fuel tank in the GEN II is not a fixed volume, but rather is a flexible plastic bladder whose volume is sensitive to cold, the bladder, some how, may have buckled/contracted down in gasoline holding capacity to a smaller available fuel volume, and is "stuck" there.

Your "...still 6 gallons left in the tank, as when I fill it at 1 bar it takes about 6 gallons of tank to fill it...even though gauge is showing empty but there is half a tank of gas still in the car" may be an erroneous assumption. When you are at "1 Bar" you may, in fact, be running on a nearly empty fuel tank. See what happens to this problem when the weather warms up. If it is not a problem related to the cold sensitive, flexible fuel bladder, then it may be the fuel level sensor in the gas tank.

 

This sounds pretty normal. The fuel bladder capacity is inconsistent. I believe the capacity spec is a fair bit higher than its real-world capacity.

Do not continue to drive on 1 pip thinking you have half a tank left (you don't). Instead, get into the habit of filling up at 2 pips. You don't want to run out, for numerous reasons.

Try to fill the tank more slowly to allow the bladder to expand. Use only the first click on the filler nozzle. Some also stop partway through and pause before continuing, but I've never tried that.

The most I've ever gotten into the tank at a fillup is a little over 8 gallons, on a warm day. My typical fillups are 7.something and if the weather's cold, 6.something.

 

how long have you owned her?

 

It'll likely continue to be right about the same, aside from temperature-related variation. My Dad and I have had our '07s since new and that's exactly how they are: 6-8 gallon fill-ups. The fuel capacity specification doesn't mean much with the 2nd-gen Prii.

 

It is incorrect for you to assume there are "a few gallons left" when the fuel gauge shows 1 bar. And when that 1 bar starts to blink, that is a sign you are really about to run out of fuel. When the car runs out of fuel, an out of fuel trouble code is logged by the engine ECU.

After the gasoline station fuel pump first clicks off, try to pump another gallon or two into the tank, if you are concerned that you can normally pump only six gallons. That is the one way for you to see whether the gasoline station fuel pump is clicking off prematurely.

 

why not put a 5 gallon container in the back, drive until you run out (somewhere safe) and start fresh?

 

I bought my 2009 Gen II Prius in January 2014, and I've always tried to avoid letting the tank get below about ¼ full (fuel pump is in the tank and is is likely to overheat (and develop problems) if gas level gets too low). The most gas I've squeezed in in one fill over the past year is 8.55 gallons, and I always fill until the pump cuts off (automatic) and then two more clicks (to avoid overfilling and damaging the emissions plumbing & stuff) and bearing in mind that the summer gas formula is different to that used in the winter (here in the North East), my best/worst gas mileage in the (last) summer has been 64.50/41.20 and 47.55/33.20 this past winter. I also have a couple of ScanGauge IIs which I also use to monitor the fuel consumption, and I find the built-in fuel gauge to be pretty accurate (bearing in mind the flexible baggy thingy the fuel is carried in) I usually get gas at the same filling station each time - hope this helps - Wil.

 

My understanding is that the computer will not shut down the engine when fuel is still available, the engine will keep running as long as it can draw fuel from the tank.

But as Patrick already pointed out, you don't really know how much fuel is actually left in there. That Gen2 bladder throws in a major monkeywrench of uncertainty. Many Gen2 drivers have reported no problems, they have driven considerable distances on the flashing pip without running out. But not all have been so fortunate, a significant number have run out very early. I seem to remember JimboPalmer getting a mere 7 miles on the flashing pip before his tank ran dry. A few other members here actually ran out before the last pip started flashing, two solid bars were still displayed. These seemed likely to be related to gauges out of calibration, but the important point is that the drivers had no advance warning.

If you really need to know how far your particular car will go, you'll have to actually test it. Intentionally run it out of fuel (or a long ways past the last low fuel warning) and see just what happens. I've done this on two other cars (not Prius), carefully selecting the time and location and weather and traffic conditions to minimize the inconvenience of getting stranded, and bringing along a big can of spare fuel (which is a significant safety hazard). I got my answers with minimal inconvenience. Bob Wilson has done this 50-ish times in a couple Prii for a variety of engineering tests, also with no difficulties. But some others who ran out unintentionally, without preplanning, have required service calls and tows to Toyota service shops to get their cars running again. The Prius computers demand a certain minimum amount of fuel to be added to the tank before trying again, and allow only a few restart attempts before locking out additional tries outside the shop. Don't even consider trying this if you have a schedule to meet that day.

Then, after getting your answer, beware that the Gen2 bladder still throws in considerably more variability than non-bladdered tanks. The car could die at a much shorter distance next time.