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Richie72

Fuel Meter Problem

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Hi All,

I have problem with my FUEL METER on my 94 LS400 won't go up until I have drove it for a long while. And it won't go all the way up to full either; eventhough, I just filled up my tank. if anyone have any idea how to fix this issue, please help. Thanks

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I have the same problem on another car... I've tried using fuel system cleaners..chevron w/ techron, Shell, Seafoam but the needle still moves extremely slow but it does get to full.

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Hi All,

I have problem with my FUEL METER on my 94 LS400 won't go up until I have drove it for a long while. And it won't go all the way up to full either; eventhough, I just filled up my tank. if anyone have any idea how to fix this issue, please help. Thanks

It is highly likely that you have the following problem;

http://us.lexusownersclub.com/forums/index...?showtopic=5822

If not then it could also be the fuel sender, which is the sensor that determines the fuel level in the tank by sending a variable resistance signal back to the combination meter (instrument panel). The way to check is to access your fuel tank and carefully disconnect the 3 pin connector (from the '92 manual is connector F21) which has the Green with white stripe, Yellow with Black stripe and violet wires. Take a resistance reading between the two terminals that are connected to the yellow/black and violet wires (have a look at the attached file, it also shows which terminals are 2 & 3)

F21 FUEL SENDER

Continuity between terminals 2–3;

APPROX. 3 ohms AT FUEL FULL

APPROX. 110 ohms AT FUEL EMPTY

Unfortunately neither is easy to check!

fuel_sender.bmp

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Actually, I had similar symptoms and the cause was pretty simple for me to fix.

I have a '90 LS400 with over 300k on it and the gauge started giving me random readings sometimes. Often not reading full when filled, or falling extremely quickly then reading empty at times. The cause was dirt/grime on the end of the arm of the fuel level float.

The directions to fix this are from memory, but it was pretty straightforward. When my tank was well under half full, I pulled out back the lining at the back of the trunk revealing a circular cap or sorts on the gas tank with a couple connectors coming out of it. I then removed the cap, took out the float and orange warning light sensor and carefully took apart the end of the fuel level arm that it pivoted from. Inside of this is a printed circuit that varies the resistance as the fuel level changes. I carefully cleaned it off closed everything back up and the problem was fixed. It is important to make sure that you do not bend the small piece that makes contact with the printed circuit or you will get no reading at all (if you bend it away) or your tank's readings will no longer be as accurate.

Alternatively, a new mechanism is not the most expensive part ever if you can determine that this in fact the problem (and not the instrument gauge, etc).

Good luck.

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The fuel gauge on my '94 LS instrument cluster started to act up a little over a year ago, and after reading all the threads on this common problem, I sent the cluster to Jim Walker, who is mentioned frequently here. He provides the cluster removal instructions-it's not too hard to remove it, even for a fumblefingers. I got the cluster back in a week, and couldn't be happier. The cost was $225 US total, so that's a real bargain for those overseas, since you-know-who has proceeded to make the US dollar worthless. I recommend this overhaul, since Jim also replaces all the other capacitors and such, and as a result, other cluster lighting future problems are also remedied.

Best of luck.

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-=93 LS400=-

I too also have a weird case of fuel level management. I swapped clusters in mine because the original one was flickering on and off too much so I installed one from a donor car. The old cluster was showing about a 1/4 tank. When I swapped them out, the replacement cluster was nice and bright, all the needles glowed like they should, no flickering, and I gained another 1/4 tank of fuel!! So I thought!! Turns out My gauge never drops below 1/2 tank even when its out of Fuel!! I found out the hard way. I put in 5 Gallons of fuel and the gauge goes up to a Full Tank!. How could this be??

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-=93 LS400=-

I too also have a weird case of fuel level management. I swapped clusters in mine because the original one was flickering on and off too much so I installed one from a donor car. The old cluster was showing about a 1/4 tank. When I swapped them out, the replacement cluster was nice and bright, all the needles glowed like they should, no flickering, and I gained another 1/4 tank of fuel!! So I thought!! Turns out My gauge never drops below 1/2 tank even when its out of Fuel!! I found out the hard way. I put in 5 Gallons of fuel and the gauge goes up to a Full Tank!. How could this be??

The stepper motors used in the early Lexus gauges had lots of problems... They are hard to calibrate and easily fail :(

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-=93 LS400=-

I too also have a weird case of fuel level management. I swapped clusters in mine because the original one was flickering on and off too much so I installed one from a donor car. The old cluster was showing about a 1/4 tank. When I swapped them out, the replacement cluster was nice and bright, all the needles glowed like they should, no flickering, and I gained another 1/4 tank of fuel!! So I thought!! Turns out My gauge never drops below 1/2 tank even when its out of Fuel!! I found out the hard way. I put in 5 Gallons of fuel and the gauge goes up to a Full Tank!. How could this be??

The stepper motors used in the early Lexus gauges had lots of problems... They are hard to calibrate and easily fail :(

so how do I reset it to match the resistance being sent by the sender? Is there a Calibration procedure for matching the Gauge with the sender?

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Wow, an issue that I have actually not had?! I am going to pat my LS400 on the hood. lol. Yeah, I have read alot of this issue, but strangely mostly on the 1993-94 models. I didnt have the problem on my old 1990 LS or my current 1991 LS. I kinda always thought it was the actual gauge itself - I thought perhaps they had done something differently with the panels on the 93-94 models since they were different than the 90-92 models. Guess not, as it seems like its the meter in the tank itself.

However, with both of my LS400s, it did (90) / does (91) take it a couple of minutes to go up to full when I fill it up, but both were like that since day 1 when I bought them.

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