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98 Ls400 Fuel Indicator - Improper Indication


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I have a 98 LS400 with approx 198K miles. About a month ago, I filled my car up with gas and the needle went beyond the full mark that it never been before. I thought that was strange, so after driving 130 miles, the fuel indicator still indicated FULL. That's when I figured I had an issue. I still have the issue. I monitor my fuel by approx. miles on the instrument panel. Anyone have ideas on how to fix this problem??

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If this happened after you filled up with gas it may be that the sender unit float has stuck and has not fallen as the level in the tank drops,you could opening the trunk and giving the tank a thump to see if this will make the sender float drop down again.

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If this happened after you filled up with gas it may be that the sender unit float has stuck and has not fallen as the level in the tank drops,you could opening the trunk and giving the tank a thump to see if this will make the sender float drop down again.

I will try that. When my tank is empty, the fuel indicator is at the half tank mark. Like I said, I'll try that and see what happens....

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Normally if you take the sender wire off the sender unit the fuel guage should read empty and f you earth/ground the wire it should read full.If this happens it would suggest the sender unit in the tank is faulty.If the guage still acts up it would be more likely to be the guage/instrument pod causing the problem

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If the sender does need replacing, the attached TSIB provides information about its location and how to get to it.

Thanks for the info. The trunk slamming and the knocking on the fuel tank didn't fix the problem. I will look into the sender unit. I am having various issues all at the same time with this car. I still love it, but working on each problem....

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Normally if you take the sender wire off the sender unit the fuel guage should read empty and f you earth/ground the wire it should read full.If this happens it would suggest the sender unit in the tank is faulty.If the guage still acts up it would be more likely to be the guage/instrument pod causing the problem

I took the green wire off and I think that goes to the pump perhaps? I say this because the car was about to cut off and I reconnected it. I'm assuming the other wire goes to the sender unit for proper indication.

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Normally if you take the sender wire off the sender unit the fuel guage should read empty and f you earth/ground the wire it should read full.If this happens it would suggest the sender unit in the tank is faulty.If the guage still acts up it would be more likely to be the guage/instrument pod causing the problem

Here's what I did a few minutes ago. I disconnected the sender unit wire that goes to the fuel indicator, then I started my car. It indicated like it should since I don't have much gas in it and the refuel soon light came on. When I reconnected the wire it still indicated as such, but when I turned the car off and restarted the car, the indicator went back to half tank reading....

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Replace the sender or if you don't want the expense use the trip meter to tell when to refuel. Reset it everytime you fill up and then once you hit say 300 miles or so refill. Maybe for a '98 that is too much of a bandaid but if it were a '90 with 250k+ miles I would not bother fixing the sender.

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The sender is less than $60 from http://lexus.sewellparts.com with a car forum discount. Is it harder to replace than it looks? Or I guess you could pretend that it's a 1950's VW Beetle that didn't come with a fuel gauge and use a stick to check fuel level.

As it appears, it's not hard to replace, but once I begin the maintenance, I'll see.

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  • 2 weeks later...

The sender is less than $60 from http://lexus.sewellparts.com with a car forum discount. Is it harder to replace than it looks? Or I guess you could pretend that it's a 1950's VW Beetle that didn't come with a fuel gauge and use a stick to check fuel level.

As it appears, it's not hard to replace, but once I begin the maintenance, I'll see.

Replacing the sending unit isn't hard at all. You just have to disconnect two electrical wires and remove 6 bolts and washers. I've replaced the sending unit, but the problem still exists. I purchased a used fuel sending unit and the person I bought it from said it was operational. I either try more troubleshooting with another part or purchase a new fuel sending unit. Any suggestions?????

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  • 2 months later...

All the needles are acting up on the instrument panel. The temperature is reading above normal ops temp, the speedometer sticks at zero until I drive for a while as well as the tachometer needle. It sticks at zero for a few seconds or so then it jumps up. Same problem exists with the fuel needle gauge as before. When the tank is empty, the needle is a little below half-tank. I'm thinking it's the instrument panel. Any inputs and if it's the panel, anyone have instructions on how to remove it?

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I'm thinking it's the cluster too because the temp gauge needle is higher than normal, RPM gauge sticks sometimes for minutes, the speedometer needle sticks sometimes for minutes, as well as the crazy fuel gauge needle not accurately measuring the fuel inside the tank. Any info on how to remove and replace the cluster, get a new one, etc.???

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  • 6 months later...

Well, I finally installed a brand new fuel sending unit and the fuel indicator still reads improper. I disconnected the connector and of course when I switch the key on, the needle is reading close to empty (approximate mileage indicator shows low fuel). I guess next I will focus towards the cluster........ :wacko:

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wow. you went all winter with this condition? You certainly have more patience than do I.

What I would suspect is a bum connection to the instrument panel. Intermittent power/ground or such. Have you tried tapping (somewhat gently) on the instrument cluster or rapping on the dash to set up vibrations. Good vibrations of course. ^_^

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  • 2 weeks later...
  • 4 weeks later...

In the past when this problem occurred, I removed the meter, but didn't open it. I thought maybe it would have been a connection problem, so I removed it and reinstalled it. I even tapped on it lightly. I'm going to be very happy when I ever figure this out. For the last month or so, I haven't been working on the issue. Maybe something or someone will shed some light soon....

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  • 5 years later...
On 6/9/2012 at 6:13 PM, Lexus79 said:

In the past when this problem occurred, I removed the meter, but didn't open it. I thought maybe it would have been a connection problem, so I removed it and reinstalled it. I even tapped on it lightly. I'm going to be very happy when I ever figure this out. For the last month or so, I haven't been working on the issue. Maybe something or someone will shed some light soon....

My 1998 LS400 had fully functioning fuel gauge until one day this past week I noticed it stayed full beyond what it should have. Towards the end of the tank it dropped to half. I just replaced the fuel sender with a brand new OEM and the fuel marker stayed at half even though the tank was mostly empty. I am puzzled and frankly not sure what to do anymore. I don't want to spend a fortune fixing the instrumentation cluster and see the problem still persisting. Fortunately the trip computer seems to be working so I have a good idea when the gas tank is getting low. Actually a little annoyed cause the original fuel sender is probably working fine.

fuelsender

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