Many of us suffer from the dreaded fuel gauge problem; up, down, fast, slow…it seems that the symptoms can vary from one vehicle to another. On my rig, the tank shows full for 20 miles or so, then drops like a rock to just above halfway, where it remains until 100 miles. Then it does a normal “descent” to E, or about 230 – 250 miles.

Well, as I dropped my tank to install my Walbro 190 fuel pump the other day (in anticipation of my supercharger install), I figured it would be a perfect time to look at the sending unit and see if I could spot the problem.

This first picture is the fuel pick-up unit in its entirety (with the Walbro 190 installed already). It is obviously upside down. The sending unit is that gray open “box” bolted to that arm. In addition, you can see that little metal arm with a small bend going out of the picture to the float. The sending unit is what we will be concentrating on. Because the unit is upside down in this picture, the sending unit is maxed out on “full.” So keep that in mind.




Now, here is the money shot. Sorry it’s blurry. You can see how the contact piece travels up and down the points in relation to the float level in the tank. Again, this is upside down, so it is on full. Do you see the black on the points between full and just above halfway? Well, that is exactly where my problem is on the gauge itself. Coincidental? I think not.




I am no electrical engineer, but I know a thing or two about how things work. I am pretty sure this is our problem. Unfortunately, I don’t have a solution, nor did I have time to mess with mine. My gauge does not bother me much, so I didn’t want to make it worse. I can see why the dealer just replaces the unit as a whole. It is possible that it cannot be fixed anyway. So there you have it, my theory as to why the fuel gauge problem exists.

 

Good work Christian!!! btw...I hope that's not blood on those towels?

I don't have this problem now, thank god...but my 99 Tacoma did.

 

Thanks! actually, it's K&N oil (from the cone filter on our Accord).

 

it may just be the angle, but couldn't you use some cleaner, maybe acetone or something and clean the connection points?

 

I don't know, but I sure as heck aint pulling that tank again if I can help it!

Maybe an eraser to a pencil would work

 

Yes, an old pencil eraser would be the best way to clean those contacts (use a new pencil, erasers get crusty after time and don't work as well). You might also have the pull the contact arm off and clean it too to make it work 100% again. It is just a big potentiometer (variable resistor), no worries there.

 

was the tank difficult to pull out?

 

With air tools it took me about 4 hours from start to finish. And that's with the FP install in between.

 

There are two independent issues:
1) Low fuel light comes on with 4-5 gallons left, instead of the 2 or so where it should. Caused by the sending unit being miscalibrated. Fixed by replacing sending unit.

2) Fuel gauge reads erradic. Caused by a faulty levelling circuit on the #3 dash panel PCB. Fixed by replacing this PCB. Somewhere I've read that the levelling circuit can be hacked and the gauge work properly, although the details of what precisely got hacked are vague. If you remove the dash panel, the levelling sensor itself is the white plastic thingy mounted on the back side with 3 small wires connecting to the gauge PCB.

It could be that if the sensor were disconnected, and the gauge recalibrated via TSB EL010-99, then the gauge might work ok. I didn't try this when I replaced mine, but since I still have my old PCB, I might.

 

Good point about the light coming on. I don't have that problem, so I didn't look into that further. I only have the screwy fuel gauge problem. It would be interesting to see if someone with both problems could fix or possibly alleviate the issues.

Anyone know how much a properly functioning sending unit costs? I guess if you have the dang thing pulled then you might as well replace the whole darn thing if the cost is within reason.

 

I have the fuel ligh coming on with 4-5 gallons left problem. I think the sending units are pretty expensive, I guess I'll just live with mine.

 

<96 Runner> if you are discussing your 96, I don't think these things apply. TSB EL010 applies to 99 and 00 4Runners. Your 96 may very likely just have a sending unit problem, not a levelling sensor circuit problem.

Anyways:

The sending units are about $80 or so I think, so they are cheap enough. It just takes the time to R&R the tank.

The pick-up tube assembly is another $80, but you don't need it. The difference between the old pick-up assembly and new one is that the new one has a shorter vent pipe, allowing the tank to fill a little more quickly as it approaches being full. No reason why you can't hacksaw your pipe an inch or so, using the photo below as reference.

See this thread and photo of pick-up tubes

 

Too bad you didn't take a multi meter to the sending unit output and measure resistance as you move the float arm up and down. All you would need to do to correct the guage reading (assuming the potentiometer is working.....ie varies linearly) is to add the proper value of resistor inline on the sender (this could also be done at the PCB where the sender input comes in). Then it would read correctly. If you were unsure which value of resistor to put in, you could solder a pot in line, vary the resistance to make the sender read correctly for the amount of fuel in the tank and then remove the pot, measure the resistance and then solder in the proper resistor value.

 

i didn't read every post exactly

but walking through advanced auto parts one day to get some fuel injector cleaner.... I saw a bottle in w/ the cleaners that was called fuel sensor cleaner. You pour it in ur tank like fueld injector cleaner and fill the tank and it's suppose dto clean up the sensor.. I forget who made it but i know it has a picture of a fuel sensor on it (like the little array of lines.

I am gonna go back to advanced next week and check it out... maybe pick up a bottle, b/c i am having some fuel guage problems.

--Jared

 

Heres a TSB I found on Alldata,

Electrical EL010-99 99 & 00 4Runner

Vehicle has to be sitting on a level surface with an inclination of +/- 0.5 degrees.

1.With the ignition switch in the Off position, press and hold the trip speedometer reset button.
2. Continue pressing the reset button while turning the ignition switch to the On position.
3. Within 5 seconds of turning the ignition switch On, release the trip switch, press trip switch 3 times and on the 3rd press, hold the switch for 5 seconds. The buzzer will sound for 1 second at 800HZ.
4. After the buzzer stops, release the trip switch.
5.Press the trip switch one more time and hold for 5 seconds. Once more the buzzer will sound for 1 second at 800HZ.

Worked like a charm on mine, hopefully it will work on yours too!

 

Seriously though, I wish there was something like that for 96-98 4runners.

 

Is this for real? I've never heard of anything like that?

 

Call your dealer and ask about TSB [ Technical Service Bulletin ]

EL 010-99

It is about the fuel gauge problem.

Worked great on my drop like a rock gauge.

 

Ringmaster-

Do you have the replacement circuit board mentioned in the TSB? I thought the code only worked with the replacement, not the original (defective) circuit board. If it works with the defective one, I am trying the code tonight!

Thanks-
Scubaduck

 

Scubaduck, nope same old board. I thought I'd try it and see, and it works.