70 Series Fuel Gauge anomalies

Joined
May 6, 2010
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340
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Vernon, Canada
Now I know there are others out there that have the gauge issues that I have, and I am wondering if anyone had found a right proper fix for it?

The issue to the uninitiated is this:
- Fill fuel tank up, guage reads full and normally
- For the first 1/4 tank the guage seems to work fine, but from 3/4 - 1/2 tank the guage tends to drop down near the empty for the whole last half the tank.

This would drive me crazy except for the one redeeming factor that the low fuel light (not sure if all 70's came with this) seems to work properly and come on around 15 or so litres of fuel left in the tank so I know when I really need to grab more fuel. I can also keep resetting the trip meter and I know I am getting low when I am around 600km travelled.

Still, if someone has replaced the sending unit in the tank or found some other verified fix, would you mind chiming in? I did several searches of the forum using the inherent search tool, but nothing came up for the fuel gauge.

Thanks all, and happy new year... :bounce2:
 
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Gun Runner 5

First and Final Warning!!
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Oct 22, 2009
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Now I know there are others out there that have the gauge issues that I have, and I am wondering if anyone had found a right proper fix for it?

The issue to the uninitiated is this:
- Fill fuel tank up, guage reads full and normally
- For the first 1/4 tank the guage seems to work fine, but from 3/4 - 1/2 tank the guage tends to drop down near the empty for the whole last half the tank.

This would drive me crazy except for the one redeeming factor that the low fuel light (not sure if all 70's came with this) seems to work properly and come on around 15 or so litres of fuel left in the tank so I know when I really need to grab more fuel. I can also keep resetting the trip meter and I know I am getting low when I am around 600km travelled.

Still, if someone has replaced the sending unit in the tank or found some other verified fix, would you mind chiming in? I did several searches of the forum using the inherent search tool, but nothing came up for the fuel gauge.

Thanks all, and happy new year... :bounce2:
First of all, when you use goofy words like “liters” it confuses us Americans and using terms like kilometers doesn’t help either. 😁
 
Joined
Jan 23, 2012
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Everett, Wa
I have a whole different problem. When full my tank only reads 3/4, then as it drops it catches up. There is not empty light on mine either (BJ73 from Spain) and I wish there was. I just use the trip counter to tell me when I should likely stop and refill. Interested to see the cluster with the empty light if you have a photo handy though.
 
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Whitefish/Bozeman, MT
My '91 LJ78 never reads all the way full (just under the top line on the gauge) and drops slowly until the halfway mark, then quicker after that. I usually fill up at around 650km when the needle reaches the E line, but rarely put more than 17-19 gallons in (64-72L). I have no empty light. Some time I want to put a 5 gallon jug of diesel in the back and drive until the tank runs out so I can see how much it takes to fill it all the way up; I'm not sure it can actually fit the advertised 90L.
 
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Calgary, AB
My '91 LJ78 never reads all the way full (just under the top line on the gauge) and drops slowly until the halfway mark, then quicker after that. I usually fill up at around 650km when the needle reaches the E line, but rarely put more than 17-19 gallons in (64-72L). I have no empty light. Some time I want to put a 5 gallon jug of diesel in the back and drive until the tank runs out so I can see how much it takes to fill it all the way up; I'm not sure it can actually fit the advertised 90L.
IIRC, I think @OGBeno once posted that the Toyota empty light turns on with 5 gallons left, which would mean 90L total.
 
Joined
May 6, 2010
Messages
340
Location
Vernon, Canada
I have a whole different problem. When full my tank only reads 3/4, then as it drops it catches up. There is not empty light on mine either (BJ73 from Spain) and I wish there was. I just use the trip counter to tell me when I should likely stop and refill. Interested to see the cluster with the empty light if you have a photo handy though.

Once in a while, my gauge will go back up a bit, usually after being stopped and started again (pressure in the tank releasing? Electrical reset on sending unit?) but for the most part the symptoms for me as are described above.

Again, I am not sure when/what year they added the low fuel warning light, but generally speaking if I add fuel not long after that I can usually only get about 75 litres into the tank, which tells me there should be around 15 still in there.

here is a shot of my 2002 dash as per your request:
dash1.jpg


A little closer in, below the fuel gauge there is a rectangular panel where the low fuel light is . When it illuminates, it is orange in color. I had just filled it up, so I can't show you the dash with the light on.

dash2.jpg


This picture from the manual (sorry I do not read/speak or understand Japanese) shows where the low fuel light is:
dash3.jpg


At least this light has been consistent, unlike the gauge itself. That and the trip meter is what I use for sanity checks. So the gauge anomalies are more of an irritant than anything. I just don't want to replace the sending unit in the tank and have it act the same... I don't want to throw parts at it like the stealerships like to do. Hence the call out to the infamous 70's community of brethren to tap into the collective knowledge therein. 🤔
 
Joined
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Messages
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Vernon, Canada
My '91 LJ78 never reads all the way full (just under the top line on the gauge) and drops slowly until the halfway mark, then quicker after that. I usually fill up at around 650km when the needle reaches the E line, but rarely put more than 17-19 gallons in (64-72L). I have no empty light. Some time I want to put a 5 gallon jug of diesel in the back and drive until the tank runs out so I can see how much it takes to fill it all the way up; I'm not sure it can actually fit the advertised 90L.
From the sounds of it you are filling up just before the low fuel light (if you had one) would come on anyways. I would probable only be at around 500-550km at this point with mine. Though I do not get the same mileage with my 1hz that you get with your germapanese hybrid! For that, I just jump in the actual TDI jetta!

If anyone can read Japanese I can take a picture of my manual pages and we can see what it says about WHEN the actual low fuel light comes on. as stated by Ben, he says 5 Gallons... that seems to be right because I figured from my experience it is somewhere around 15 Litres fuel left when I fill up after it comes on.
 
Joined
May 6, 2010
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Vernon, Canada
Excellent suggestion! I downloaded the google translator app (I did not know they had a camera/scan option to their app)

Grammar aside, lol... the consensus from the factory owner's manual for my specific 76 series says the low fuel light should come on @ 12 Litres of fuel remaining. Allowing for some differences due to slope, etc, it may come on earlier than that.

Now, back to our earlier programming - hail one, hail all, hear ye hear ye.... Has anyone gone through the trouble of finding a fix, whether replacing the sending unit in the tank actually gives a consistent, normal reading on the gauge? Or any other fix I may not have heard of?

Thanks all!
 

GTSSportCoupe

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My gauge has issues too. Starts very slow, and then falls faster and faster as the tank level goes down. Full indicated is full, 3/4 indicated is 1/2, 1/2 indicated is 1/4, etc. Makes it seem like I'm getting good fuel economy for the first half of the tank at least, haha.
 

FJBen

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My gauge has issues too. Starts very slow, and then falls faster and faster as the tank level goes down. Full indicated is full, 3/4 indicated is 1/2, 1/2 indicated is 1/4, etc. Makes it seem like I'm getting good fuel economy for the first half of the tank at least, haha.

that's exactly how mine works. I get usually 350~400kms on a 1/2 tank, then only 250ish on the last 1/2. In the summer I got better, but for the life I've owned this 13BT, it's averaging right at 20mpg US
 
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May 16, 2008
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Hello,

It may be worth checking your fuel tank piping.

The tank gauge sensor requires a closed system to work properly.

A loose or worn pipe causes the fuel level sensor to behave erratically.

So does an aging fuel tank cap.

On the other hand, and perhaps due to the way Toyota does things, from Full to half the needle moves slowly. From half to Empty the needle moves faster. And yes, there are 5 gallons / 18.9 liters left when the light goes on.

I remember reading that the manual advises not to go below one quarter of a tank very often, because it may damage the fuel system.





Juan
 
Joined
May 6, 2010
Messages
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Location
Vernon, Canada
Thank for the suggestions Juan.

I do recall that all my other cruisers and for that matter most vehicles I have owned the top half of the tank lasts much longer than the last half. But I should point out that by the time I am at or even just before I have used half of the actual fuel, my gauge reads right down by empty, and will do so (with occasional fluctuations) for 300 or more km's

By occasional fluctuations, I mean it will occasionally vary between a quarter and just above empty for that 300km. The fluctuations usually occur when I have not used the Land Cruiser for a while, then start it up again. But it doesn't always do it. What is consistent so far is the low fuel light comes on when it really is nearing empty. My owners manual states that occurs when there is around 12 litres of fuel left.

I will inspect the piping, and pickup a new filler cap as suggested. Thanks!
 
Joined
Jun 27, 2021
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Chatham Islands
I have a (new to me) 2007 V8 diesel single cab and am chasing similar gauge issues, but after pulling out the sender unit yesterday I'm confused by references to fuel tank pressure, fuel cap integrity, pipework and their potential impact on the fuel gauge accuracy.

Can anyone shed light or point me to a link that explains this please?

I saw (when I removed the sender) a cylindrical device which I assume is the low fuel level warning light float switch (my light doesn't seem to work so make not be fitted), but the fuel gauge sender operation seemed to be a simple triangular float attached to a variable rheostat (or something like that).

Is there more to the puzzle than the sender and gauge?
 
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I found out that my HZJ77 has the low fuel light when it came on once. Never seen it in the FJ73 or PZJ70 I had. I usually fill up way before I get that low.
 
Joined
May 6, 2010
Messages
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Location
Vernon, Canada
I have a (new to me) 2007 V8 diesel single cab and am chasing similar gauge issues, but after pulling out the sender unit yesterday I'm confused by references to fuel tank pressure, fuel cap integrity, pipework and their potential impact on the fuel gauge accuracy.

Can anyone shed light or point me to a link that explains this please?

I saw (when I removed the sender) a cylindrical device which I assume is the low fuel level warning light float switch (my light doesn't seem to work so make not be fitted), but the fuel gauge sender operation seemed to be a simple triangular float attached to a variable rheostat (or something like that).

Is there more to the puzzle than the sender and gauge?
When under use, the tank can become pressurized, and I would have to think the engineers at Toyota worked this into the mechanics and electronics of their vehicles. Having a fuel cap that does not seal properly can affect emissions and (potentially) the behavior of the float in the tank while driving. Now your 2007 with the V8 is probably all controlled by an ECU, so not sure if it will be the same issue or not.

I have yet to grab another fuel cap, I was waiting until I had a few things to order all at once, and I would prefer to get an OEM one.
 
Joined
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Vernon, Canada
I found out that my HZJ77 has the low fuel light when it came on once. Never seen it in the FJ73 or PZJ70 I had. I usually fill up way before I get that low.
Nice find! At least it is nice to know you have one.

I was on my way home on the weekend, pulling my 12ft enclosed trailer when my fuel light came on... I only had around 30km/18.5 miles to town so I just kept motoring. When I got to town and filled up, it is the most I have ever put into it... 84 litres, and the tank is supposed to be 90. 😦 Of course, when the needle reads down by the E for the last 300kms, it is hard to tell when I should actually fill it up.

I usually fill up before the light comes on too...
 
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Vernon, Canada
Ok, so I thought I would post back here with what seems to have corrected this odd behavior.
A shout out goes to @JuanJ for his suggestion for a NEW FUEL CAP.

I put one in last weekend, and the gauge worked much more normally and consistently. You can definitely see on the old cap the seals are rock hard. I just went into a generec automotive parts shop and got a default Land Cruiser fuel cap and it fit well and it obviously seals up properly as when I went to fuel up yesterday and loosened the cap it sucked air (there was a good vacuum seal).

Hopefully this helps out someone with a similar issue!
 
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May 16, 2008
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Ok, so I thought I would post back here with what seems to have corrected this odd behavior.
A shout out goes to @JuanJ for his suggestion for a NEW FUEL CAP.

I put one in last weekend, and the gauge worked much more normally and consistently. You can definitely see on the old cap the seals are rock hard. I just went into a generec automotive parts shop and got a default Land Cruiser fuel cap and it fit well and it obviously seals up properly as when I went to fuel up yesterday and loosened the cap it sucked air (there was a good vacuum seal).

Hopefully this helps out someone with a similar issue!
Hello,

I am glad your fuel system behaves as it should now.





Juan
 

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