Need Advise: Fuel Gage Reads Incorrect Quantity

[LexusPete]

I recently purchased a 1993 Lexus LS400, and soon discovered some nagging problems (one of which is the fuel gage). The gage does not read the proper quantity of fuel. When the tank is topped off, the gage max out at less than 3/4 tank. The gage is also very slow to respond (takes 30 minutes or more to register approximate quantity). Everything else on the instrument cluster works fine, so I don't suspect the cluster.

I suspect the Sending Unit or a "Gremlin", but I want to be sure since Lexus parts are so !Removed! expensive. How do you effectively troubleshoot a sending Unit? Anyone out there who knows the scoop on this problem, please respond. I would be grately for any suggestions.

Signed:

First-time Lexus owner who is now convinced that Lexus is the largest producer of lemons.

[90LS400Lexus]

The "s l o w" movement of the fuel gauge is typical of 80s and 90s Toyota-Lexus cars. My old late 80s Camrys, as well as my recently sold 1993 Toyota Camry LE V6 (similar to Lexus ES300) also had slow registering fuel guages. Also too- my 93 Camry would not go all the way to "FULL" when I filled the tank up. It would be just below the "F" line. Very irritating I know.

My 90' Lexus LS400 is also a little slow to register compared to my Buick, but not as slow as my old Camry, nor does it take 30 minutes to properly register and it does go to "F" when full. I think it takes about 2 minutes to go to full.

Thirty minutes definitely seems excessive for a guage to register and then it should go to full. One good thing about my 92 Buick, is that it instantly registers, but the General Motors fuel guages are bad for excessive fluctuations. It could read 1/2 tank and then show 1/4 tank as you round' a curve.

I suspect you may have a problem with your sending unit or guage?

Good luck.

[SKperformance]

It is a common problem with the gauge cluster.

DO a search and you might find the fix.

[obergc]

Others have reported to have fixed the inaccurate and slow fuel gage reading by replacing some electrolytic capacitors on the powersupply board in the instrument cluster.

Curt O

[LexusPete]

Curt,

I guess I would need a schematic to identify this power supply board. Any ideas where I could obtain one without buying a Repair Manual?

Pete

[obergc]

Pete,

The schematics for the instrument cluster are not in the repair manual. There has been an extensive amount of info on this subject written in this forum and at clublexus.com. Unfortunately a lot of the good info in this forum was lost recently. You can go to clublexus.com and search for ( 'instrument cluster circuit board is bad $1000 bucks!!!) I have the jist of this thread in the attached document. If you are handy with a soldering iron you can probably fix your problem with the info here.

Curt O

Instrument_Clust_Fixr.doc

[obergc]

Pete,

Here is a link to the most comprehensive info on the subject of instrument cluster problems, including an erroneous gas gage.

Curt

http://www.clublexus.com/forums/showthread...15&pagenumber=6

[LexusPete]

Curt,

I really appreciate the info brother. Thanks! :)

[90LS400Lexus]

I filled up my car today and checked the guage and it seems fine to me. It took it less than a minute to go to full. It went all the way to the line at the "F" and stopped. I had less than 1/4 tank in it. It held 16.6 gallons. $23.50 was the total @ 1.40.9 per gallon. The supermarkets gas station has a special on Fridays, where you can get premium gasoline @ mid-grade prices. Last Friday it was $1.35 per gallon for premium. Now that I know exactly how many gallons I put in- I am going to check my MPG.