MY PROBLEM...

"I have a 99 SR5 4Runner. Yesterday, I noticed the fuel gauge was reading more fuel than what was actually in there. Filled it up, gauge went to full and plunged to empty a few seconds later. Drove it about 10 miles with it reading empty and the low fuel warning flashing. I turned it off when I got to where i was going. When I turned it back on, gauge was reading full again. After driving 50 miles, it is still reading full, not moving at all. I see no fuse issues in the drivers compartment. Any suggestions for a fix to this? I appreciate any feedback from anyone who has dealt with a similar issue or may have knowledge to what it might be. I appreciate your help."

So it will be the fuel level sensor? i was reading that maybe is the whole system, that i should use an aftermarket system...

what do you think?

Most likely it's the fuel level gauge sending unit in the tank.
They get quirky.

thats what i was thinking, i found the sending unit at autopartswarehouse website, by a chance where else can i buy the part online?

tks. Nice Hilux!

I'm having the same problem with my 99 fuel gauge. After filling up the tank, the fuel gauge reads F for a few seconds, then drops to E and the low fuel light starts flashing. This typically happens as soon as I put it in gear and start moving. If the tank is not full, the needle reads F all the time.

The problems started a few weeks after having the gas tank dropped by the welder who was repairing my rusted frame. The connector looks OK and fits snugly on the tank. Gently tugging on the wires does not change the behavior.

I followed the FSM procedure to test the sender and gauge:

1) Unplug wiring harness and turn ignition on. Fuel gauge reads E and low fuel light comes on (not flashing). Seems to behave as designed.

2) Connect pins 2 and 3 on wiring harness with a 50 Ohm resistor. (FSM recommends using a 3.4W [~42 Ohm] bulb but I didn't have one handy.) Fuel gauge slowly moves upwards. Sometimes it behaves normally, sometimes the gauge drops suddenly to E after a few seconds and the low fuel light starts flashing again.

3) Measure resistance between 2 sets of connections on back of fuel gauge assembly. I have not done this step yet since it requires taking the entire dash apart and I don't have the time/desire (or a driveway to work in for that matter).

4) Measure resistance between pins on sender. Pin 2-3 = ~50 Ohm, pin 1-3 = ~150 Ohm, pin 1-2 = ~200 Ohm with approximately 3/4 of a tank.

Any ideas what the flashing low fuel light indicates? I can't find any mention of the flashing behavior in the FSM.

I've been tracking my miles with the odometer so I don't run out of gas, but I'd rather have the gauge working again. I don't want an aftermarket product like the Scan Gauge.

This happened to me a couple years ago, so bear with me for the lack of specific details I can give...

Mine developed this issue after connecting an improperly wired trailer!
The first time i pressed the brake pedal, it blew the taillight fuse. Replaced the fuse several times, to no avail until I disconnected the trailer plug... All of the sudden my fuel guage would drop to empty after putting the truck in gear and the low fuel warning light would start flashing. This was NOT a fuse issue, but WAS related to my taillights... I was so confused!
I spoke with two Toyota wiring gurus who both said "the fuel guage doesn't share any wiring with the taillights so it couldn't be related"... I was stumped to say the least because this all started after the trailer incident.
One thing lead to another and i decided to dive into it myself knowing they HAD to be related. While inspecting my trailer wiring harness, I noticed the ground wire had gotten hot and the wire was somewhat melted from the inside... I added a larger guage ground wire for my taillight/trailer wiring harness and low and behold, the fuel guage now functions as it should and have had no further issues since that day.

Long story short: Check the chassis grounding point behind the left rear cargo panel (in front of your left taillight) and check for loose connections or possibly a slightly melted wire. Your issue may be farther down the chain somewhere, and could have been pulled loose from the tank/sending unit during the removal process.?.

GOOD LUCK WITH YOUR SEARCH! Feel free to P.M. me if you have specific questions.

Nate

I know this is an old thread, but I'm having the exact same problem on my 99 SR5 4Runner. I'm hoping Nates_NW4Runner is still receiving updates on this...

I noticed my trailer ground wire was frayed (pinched under the hitch). I hooked it up anyway. When we were testing lights, my wife said, "they seem really dim."

Started driving and after 10 minutes or so, the gas gauge needle dropped to the bottom of the gauge and the low fuel level light started blinking. It stays like this until I shut off the engine.

When I turn the engine back on, the gauge works for a little bit, then inevitably drops and blinks again.

Mine still happens, though, when the trailer is not hooked up. It happens faster on a warm engine, so I'm assuming the trailer light wires are warming up, increasing resistance??? and that's why it doesn't happen right away after sitting for a while.

Question for you, Nates_NW4Runner, was it occurring for you when the trailer was not attached, right? And the wire you replaced was on the 4Runner? Where does that wire ultimately lead to? and is it run inside the frame channel irons?

Thanks in advance.

Nate, this is what happened to me. I connected a trailer and zap! I smelled the burnt wire. I thought the smell came from behind the dashboard. I hope your location is where I have the problem. Easier to get to. I will post my results. Thanks!!!!!!!!!!!!!!!!!

Steve

So far I have been using rockauto, they seem to have to best pricing so far.

I did as promised a few days ago and checked the brake bulbs. Before I started, gas gauge was inop and brake lights worked fine. One bulb looked a bit corroded inside; once I put it all back together it stopped working. Replaced both with new 7443s from Autozone.

I was probably around half a tank at the time. Gauge wandered a bit at first between trips but no more of the needle drop and blinking gas light. Stabilized after 2-3 days and read normally. Just added 16.5 gallons with gauge showing 1/4 tank, needle is back above F and held there for the 10 miles I've driven since then. If something changes I'll report back, but replacing the brake lights seemed to reverse whatever gremlin popped up when the battery ran down a few weeks ago.

Weird.

Alright T4R, lemme explain what's going on and maybe someone can chime in to what my problem is...

Yesterday, my gas gauge started acting up. When I started my 4Runner, it showed the correct gas level for about 20 seconds and then it would instantly drop to empty and the fuel light would flash. It did this every time I started it afterward. After reading a few different threads, it seemed like my issue was more electrical rather than the sending unit because the gas needle doesn't wander, it's either perfectly accurate or not working at all.

Seeing as the tail lights were a common culprit, I decided to check them. All the tail lights worked like normal, but after further inspecting the bulbs, one of the bulbs was black and filament between the two lead wires was kinda dangling and not really connected. Ahaa! There it is. I replaced the bulb and started it back up. Drove for about 30 seconds and the fuel level drops to empty.

I realized I forgot to re-calibrate the fuel level. After following the instructions and re-calibrating, I took it for another drive. I drove it for about 2 minutes and the fuel level is reading where I expect it to, about 3/4 of a tank. YES! I thought I might have finally solved the issue. After 2 minutes though, it instantly drops back to empty again. WTH!

A little background on my 4Runner that might give a little insight: I just installed a lift. The lift has left some rake to my 4Runner. The rear sits at about 1.5" higher than the front. I haven't gotten around to adjusting the front coilovers yet to the proper height. I drove it for 3 days after installing the lift with no gas gauge issues, and then took it in to a shop to weld on a Panhard Correction Kit (from eimkeith) yesterday. I drove it about 20 miles, parked it for 3 hours, started it and about 20 seconds later the fuel level drops. Everytime I've started it up since, it does the same thing. I checked all wires that could've been damaged when it was welded, including the trailer light wires, and nothing is out of the ordinary.

Could the rake from the lift or the weld have something to do with this? Since the burnt tail light replacement and re-calibration didn't work, I'm kinda at a loss of what it could be.

Any thoughts??

Does the fuel pump and sending unit have different electrical connectors even though they are both par of the same assembly?

Seems we all have similar problems but not identical which makes it confusing. Since I bought my 3rd gen a few months back it has been amazing but even during the test drive the gauge reads empty and the fuel level light flashes. I didn't think this was a big deal for the purchase price. I am assuming the sending unit is bad but I have learned that the sending unit and the fuel pump are the same assembly so replacing the one would mean replacing the other and having to drop the tank to do so. When I start my truck the fuel gauge spikes up to FULL then pauses for about 2 seconds and drops to empty and the fuel indicator light starts flashing. So I know the gauge is getting power. I know the fuel pump/sending unit assembly is working, otherwise I wouldn't be going anywhere. Before I start trying to locate an electrical issue in some random location I will try these simple tasks first. Check grounding cable behind left taillight area and check the light bulbs in the back...? This sounds silly but I have worked on old VW's before so nothing surprises me anymore. Other than what this thread recommends, does anybody else have any other ideas pertaining to my specific issue? Thanks.

I just recently bought a 99 Limited and the gas gauge would always show empty with the gas light blinking. Last night I added a new ground for the wire and now the gauge just reads full with no gas light. I'm not sure what to do next. Maybe I need to replace the whole gauge cluster? Please help!

I have been having this problem for years. In 2017 I posted saying that I thought that I might have had a bad tail or brake light bulb and that it was fixed. It didn't stay fixed very long. I gave up and used mileage to keep up with fuel quantity. Today I noticed that the brake light on the top of the hatchback was out. When I removed the bulb I noticed that the inside of the socket was black and burned on the inside. The socket needs to be replaced. Without the bulb installed the fuel gauge is working perfectly. I have ordered a new socket and will keep you updated as to whether it still keeps working correctly when the new socket is installed with a new bulb. Hopefully the burned socket is what is causing the short.