gas gauge doesn't move when filling

Sounds pretty normal to me. Three gallons may not bump the gauge ecu enough to register (happened to me a few times). I have also had times when a fill up of more than 1/2 a tank didn't register for quite a while (as you saw, a few start/stop cycles). Do note that the gauge doesn't drop during this time until the actual fuel level drops -below- the indicated level.

It's a digital gauge system and is easily confused. Good match to me.

 

Hoo boy! Here we go again...

The infamous and much accursed Fuel and Evap System
in all its byzantine complexity and numerous bits.

First off, to answer Tony's question:

"The direct acting fuel gauge is located in the sub tank.
[Emphasis added] This gauge consists of a pipe surrounded by a coil. A
float in the pipe moves up and down with changes in the fuel level. A
magnet is attached to the float. The up and down movement of the
float causes a change in the magnetic field. The flow of current through
the coil creates a potential difference and the resultant voltage is
transmitted to the meter ECU.

The fuel pump module assembly is integral with the fuel tank and is not
serviced separately."

There is a new to me twist; the fuel gauge --and the fuel pump -- is not
in the bladder, it is in a separate "sub tank."

The basis reference document for the Fuel and Evap System is:
http://www.autoshop101.com/forms/Hybrid13.pdf

The above text is from there, and if you look at the various
schematic drawings you can see the system represented as such.

This arrangement opens the possibility that the tube between the
bladder and subtank has become partially blocked somehow and
results in a slower than normal equalizing of fluid levels between
the bladder and sub tank.

There is another possibility, though I will admit it is improbable.
Should even some small amount of water get into the bladder,
it would collect at the bottom. Through repeated tank fillings the
water could work its way into the sub tank. Should the water get
between the magnet and coil it might throw off the reading until
it fell back to the bottom of the sub tank.

There is darn little on PC and even the Inter-web about the internals
of the fuel tank. In general it is understood that you can't
repair/replace individual components and complete replacement
of the whole tank assembly is necessary.

I would say that since the guess-gauge is still functional, albeit
more slowly than is typical, you might just have to live with it.

Sorry.

 

i think the key factor to consider is that it uses a mechanical float, no digital sensor.

IMO this reminds me of twist timers, such as one you find on a kitchen oven timer or I have them in my fitness center for timers on the hot tub jets, sauna and racquetball court. If you want it set for just a few minutes you have to turn them to at least 10 minutes and then turn it back to 5 minutes or whatever. they are unable to recognize a really small twist to the timer handle because they are mechanical, not digital. my $.02

 

Orangewingnut,

Is there any chance that your fuel tank has ever been overfilled enough
for fuel to "burp" or pour out of the filler neck?

If so, this could lead into a real morass involving one or more
charcoal canisters in the fuel and evap system.
(Refer to the technical article for discussion of this.)

Tony,

Here is a post where Galaxee's DH opened up a Gen II fuel tank and
took documenting pictures. He not only opened the metal fuel tank but
he went on to open the hard plastic sub tank enclosing the fuel pump
and sender -- total destruction of both.

It is positively stated farther along in the thread that the tank is from
a Gen II. The last few of the 25 photos shows the disassembled sender
which looks nothing like what I have in mind for the float-in-tube
spoken of in the technical article. Maybe there was one of those
unannounced mid-cycle changes on this. I don't know.

http://priuschat.com/forums/gen-ii-...n/30593-gas-bladder-exposed-2.html#post394632

 

Ah yes. The Gen 2 "Guess Gauge". We've got a 2009 so we know it well. As others have said inside the tank is a fuel bladder. It's harder/easier to expand and contract in different temps, and for other reasons. There's times you can put 10 gallons in an empty tank, other times only 8. Both times it will eventually read full.

Bob64 put up a great visual explaination of this animal at:
http://priuschat.com/forums/gen-ii-...uge-dummies-easy-understand-illustration.html

Our dealer swears up and down that the bladder is not in the brand spanking new 2012 we just bought. Hope they're right.

Good luck. My advice is just refill at 2 blips and at times you need to keep track of your fuel level in your head until your car catches up.

...Mudshark

 

And yup, we've seen the "put 3 gallons in and it doesn't register, put 3 more in the next day and it jumps up to full" kind of stuff.

 

age. that part of the tank is probably a little gummed up.

 

Hi Bill. Since one of these occurrences is completely normal (needs more than 3 gal to register), then at this point I'd consider it a one off anomaly.

First run a few full tanks through and see if the problem sorts itself out. If you're still having problems then there is a fuel gauge calibration procedure posted some place here that you could try.