Hello yotatech, while dropping the tank a several times in the past year I realized my fuel gauge isn’t accurate, well isn’t accurate after 1/4 and below. My fuel light usually kicks on at 1/4 tank and when I fill up it’ll take 12-13 gal at the pump. I have an aftermarket spectra premium tank that’s said to be 15g, but when I swapped it for my oem tank I had to cut and weld the fuel pump bracket to be about 1/2” shorter. Still took 15g to fill up so it’s around 15g.

Anyway after installing the first new tank and adding one gallon of fuel to the tank and starting it up the gauge never went below 1/8 tank and the light was nice and bright. It’s done this since I owned it and always figured it was how it was, but after talking to a buddy with a 3rd gen pickup he said his light doesn’t turn on till he hits 1/8 tank and the needle will go to E or below and he still has about a gallon of fuel in the tank. When I had to drop the tank again a couple months later I decided to ohm out my sending unit and it checked out in spec, no weird readings. So is it my gauge? Any way to check that? If it makes any difference when I fill up my tank till the first auto shut off from the pump the needle reads above full, about a needles width past F mark. Any ideas? Didn’t see anything in the FSM on how to check the gauge itself but I may just not be looking in the correct area.

1990 4Runner SR5
4x4
22re
5 speed trans

 

I'd pull the sending unit out of the tank and manually move the arm through the full swing and see what the gauge does. I've mentioned before just how little info the FSM has on gauge testing. You have to imagine a Toyota engineer sitting at a table with just a gauge, nothing else, and getting readings to establish parameters. Then imagine them a few hours later with nothing but a sending unit doing the same thing. None of their specs were determined with the components all connected together. it's why you get pretty much ohm specs and little else. This is where the EWD manual gives you SO much more diagnostic info over the FSM. It's not just diagrams.

The fuel gauge itself is a rare failure. Sending units themselves often went bad, and with your tank modification that adds a twist.
The low-fuel light typically came on when the tank was somewhere between 1/8-1/4. Even when your gauge needle hit the "E" it was common to have a few gallons still in the tank.

 

totally forgot to mention, the first time I had the tank out I zip tied the sender to the frame with the float dangling all the way down. Gauge never went below 1/8ish tank. But with the tank all the way full it goes pretty far past the full line. Almost like the entire sweep is offset. Also doesn’t drop and hit the full mark till about 50 miles after fill up.

 

The fuel gauges on many Toyotas took a while to start dropping after filled. The other common complaint was that it seemed to take a long time to reach 1/2, but dropped like a rock after that.

Maybe you have a mismatched sender and gauge? The sending unit replaced at one time with the wrong one? Can you gently pull the needle off the gauge and reinstall at a point you know is right, like completely full or empty? I’ve done that with my tach.

 

it’s the oem Toyota sender from 1990. Never changed that or any other sensors except the o2. I can try and pull the gauge needle off when it’s full and place it on the full mark? Never thought to try that, figured they would be affixed some how. I do need to split my meter to clean it, it’s got a lot of dust from last desert season. It does act like tou described. Takes quite a few miles to come off full, and once it gets to half it definitely does drop quickly. What’s funny is the light comes on by the time it hits quarter tank, even before one quarter mark if I’m climbing a steep hill. Like I said before I never knew this was weird till a buddy with a 90s pickup told me his actually gets to E when the light comes on.

 

The low fuel light should come on closer to 1/4, maybe halfway between “E” and 1/4. Coming on at “E” is useless knowledge.
Long hills did alter the readings.

 

[QUOTE=Jimkola;52489922]The fuel gauges on many Toyotas took a while to start dropping after filled. The other common complaint was that it seemed to take a long time to reach 1/2, but dropped like a rock after that.

Ain't that the truth. My 86 will take forever to drop to 1/2 full mark, then it drops like a rock. My empty light only came on once in 37 years and it was below the 'E' mark. Had 1-1/2 gallons left. At 'E' I have ~ 3 gals left. Been like that from new.

 

3 gallons remaining at E is about right. Customers often asked, but knowing their inclination to push made us always say 1-2 gallons remaining.
My low fuel light always came on at 1/8 of a tank.

one time I had a new Corolla towed in, the only problem was it was out of gas. The driver, a young college person who was clearly pissed, wanted to know why the light never came on to warn them. We explained that the base model Corolla, with its manual windows, manual mirrors, etc. didn’t have a warning light.
”Well, HOW am I supposed to know when I need gas!?
sigh…..

 

LOL. Bet you heard all kinds of stories. I am very OCD and have from day one reset my trip odometer with every fill up for 37 years. When it ht 275 miles around town i'd fill up. The numbers on the trip wheels have near faded away but I still reset it to this day. Crazy. Why Toyota didn't use the same number wheels as on the odometer as they are still like new.