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View Full Version : Odd Gas Gauge Issues... [found a cure for my problem]



bamachem
03-21-2008, 07:00 AM
In my 99 4Runner, I haven't had any issues until last week. On Thursday, the gas gauge freaked out and jumped from 3/4 tank to off-the-scale-FULL on the gauge. It stayed there no matter what the level was in the tank. I drove 250-ish miles and then filled up - still no change - that was on Monday. Now on Tuesday, I cranked it up to go to work and the gauge was still above the Full mark. I got about 10-feet down the road and the gauge dropped to off-the-scale empty and the fuel light started flashing. When I shut it off, the gauge stays put - where it should be. As soon as I turn the key on, the needle goes to Full - no matter what the level is. I can crank it and it will stay there about 5-seconds and then drop to nothing again.

On Wednesday, I did a fuel gauge recalibration using this:

1. After replacing the meter circuit plate or inclination sensor, move the vehicle to a level location. (A surface with an inclination no greater than 0.5° is the target flatness.)
2. With the ignition switch in the “OFF” position, press and hold the trip reset button.
3. Continue pressing the trip reset button while turning the ignition switch to the “ON” position.
4. Within 5 seconds of turning the ignition switch “ON”, release the trip switch, press the trip switch 3 times, and on the third press hold the switch for 5 seconds. The buzzer will sound for 1 second at 800 HZ.
5. After the buzzer stops, release the trip switch.
6. Press the trip switch one more time and hold for 5 seconds. Once more, the buzzer will sound for 1 second at 800 HZ.
7. The calibration process is completed.
NOTE:
If in the operation of step 6, the buzzer sounds higher than that of step 5, turn the ignition switch to “OFF” position and repeat the setting procedure from step 2.

The first time I did it, it worked great. The needle immediately began to fall to the correct level and all was good - for a few miles. I got maybe 5-miles down the road w/ a normal reading and then BAM!, back to empty w/ the fuel light flashing.

Weird crap. I have tried the recalibration at least a half-dozen times since then with no change in the way the gauge behaves.

I'm thinking a loose connection somewhere... Has anyone else here experienced one doing stuff like this?

I'm planning on taking the access cover off (located under the rear driver seat, under the carpet), and check the connections on the fuel sending unit and maybe even pull it and check for debris/corrosion. Any other suggestions?

Lee
03-21-2008, 07:02 AM
my friend with a 98 had to replace the sending unit... had to drop the tank to do so of course. :(

bamachem
03-21-2008, 07:13 AM
isn't there an access cover under the rear driver-side seat? i know that's where the wires go thru the floor, but i haven't pulled the carpet up yet to check... I just read the TSB and the tank has to be dropped! ufff!

here's someone who had the same issue in 2004 and posted about it on 4x4wire... link (http://www.4x4wire.com/forums/showflat.php?Cat=&Number=603781&page=&view=&sb=5&o=&vc=1) Unfortunately, they didn't follow up with their solution.

However, there was a link in that thread to THIS (http://www.larsdennert.com/4runner/fuelsender/index.htm) writeup of the Toyota TSB (http://pages.sbcglobal.net/larsdennert/4runner/fuelsender/Instruments%20-%20Fuel%20Gauge%20Inaccurate.htm) to replace the fuel sending unit...


Lucky me... my VIN falls in the category of replacing both the sending unit and the circuit board!

http://pages.sbcglobal.net/larsdennert/4runner/fuelsender/82141792.gif


however, on the positive side, mine was built at the Tahara plant where the UZJ-100's were built and was the highest-quality automotive assembly plant in the world. :D

Robinhood4x4
03-21-2008, 07:37 AM
If your access door is anything like mine then it's practically worthless.

YotaFun
03-21-2008, 07:47 AM
If your access door is anything like mine then it's practically worthless.


x2
I went to check this access panel and yeah its about big enough to fit my fist in (and I don't have the largest hands here)
So inevitably you would have to drop the tank to change out anything.
The 1st gens got luck and that panel is pretty much the size of the back seat. iirc

bamachem
03-21-2008, 11:08 AM
hell, i just may take a cutoff wheel to it and then just tack in some strips of sheet metal to re-attach the enlarged access panel. that would be easier than dropping the tank IMO.

Seanz0rz
03-21-2008, 09:11 PM
just dont cut into the tank! haha.

bamachem
03-27-2008, 06:09 PM
Ok, decided to try the easy route and so far it's paid off...

I put a bottle of Chevron Techron along with a full can of seafoam in about 1/8th tank of gas. I drove it around a bit - pretty hard - to "slosh" the fuel around a bit with the detergents in it's most-concentrated form. I then went and put about 10 gallons in it, so it was at 3/4 tank. That way, the sending unit was covered in fuel, but there wasn't so much fuel in there that the detergents were overly diluted.

Anyway, two days later and the gas gauge issue is gone.

It initially started after I had driven about 200 miles on gas that I bought at a discount store while traveling. After reading up on the issue, I found that some think that sending unit failures could be caused by high-sulfur content causing corrosion on the rheostat coils on the sending unit. Apparently, that was the cause, and now it's back to working 100%.

I'll post back up here if I notice anything else weird w/ it.

bamachem
04-01-2008, 12:29 PM
ok, still have some weirdness going on. it was cured for a while, but now the gremlin is back...

04 Rocko Taco
04-01-2008, 12:39 PM
didn't you VIN fall within the TSB?

bamachem
04-01-2008, 01:43 PM
yes, but w/ 142k, i'm a little bit over the 36k mile warranty!

04 Rocko Taco
04-01-2008, 01:59 PM
Ah, that would do it. :(

YotaFun
04-01-2008, 04:34 PM
What is your weirdness now?
Still the same?
Wasn't there a thread on TOF about a gas gauge issue similar to yours for the 99&00?
And they had the propper remedy by using the trip button for the OD?

bamachem
04-01-2008, 07:19 PM
it will still fall "dead" and the gas light will blink, but now it's random and fairly infrequently compared to every time i cranked it up a week ago.

better? yes.

cured? no.

BruceTS
04-01-2008, 07:35 PM
dropping the tank only takes about 15 minutes.......

I ended up replacing my sending unit and no more guage problems.....

YotaFun
04-01-2008, 07:44 PM
I could have swore there was a simple fix with this and now i can't find it
(like always)

bamachem
04-01-2008, 07:57 PM
sending unit is only about $60, so that's more than likely what i'll do.

MTL_4runner
04-02-2008, 05:45 AM
I ended up replacing my sending unit and no more guage problems.....


Given what you've experienced, that would be my suggestion as well.

bamachem
05-03-2008, 05:26 AM
in the last 4 weeks, i have used only name-brand fuels - no cheap gas. i have added another can of seafoam (early on) to one tankfull, and i actually did one tank of premium.

over the last 4 weeks, my gauge has been less and less erratic. this last week, it has acted perfectly normal. i'm thinking it was some type of deposit on the sending unit that has gradually dissolved with the use of fuels with high detergents and the addition of the seafoam.

it's beginning to look like it was high-sulfur gas at a cheap station that caused all this! :chair: