[Andygoodbloke]

Hi all
My fuel gauge doesn't work.
The tank has been changed and the sender unit with it I assume.
I have looked into the circuit diagrams and traced the wire to a Yellow with red stipe which should run from the tank sender right through to the dashboard.

I found a yellow with red wire around the area at the back of the vehicle where I would expect the wire to be- but can't confirm it the correct wire as when I earth it out I do not get any movement on the gauge on the dash board.

I have looked and found more yellow/red wires but think the are the rear break or indicators wires as that colour is red/yellow.

I run a new wire and plugged it into the terminal at the sender on the tank then under the vehicle and through to the dash. According to the wiring diagram it is the same wire which feeds directly into the guage on the dash. I was planning to find the at the back of the dash and cut and join. I cut and joined a yellow/red wire and the gauge still didn't move when tested. Before I cut the second wire of a similar colour at the back of the dash I thought I had better seek advise.

The wire I cut was on the right hand side plug (drivers side for a right drive vehicle) and about 3 wires down from the top. There is another but don't want to keep cutting and joining until the correct one is found.

Can anyone tell me the placement of the fuel sender wire where it plugs into the back of the dash on a SJ50?
If the fuel sender is not a standard one for the vehicle will it still work in the same way - or is this different for different senders? It looks the same as the old one out of the vehicle and mounted into the same hole with the same
If I take the tank down and remove the sender can I measure the resistance and check it is working? or how do you test the sender is working?
Has anyone used a cheap fuel sender unit off Ebay or Aliexpress - do they work as they should?
Any clues to help me would be greatly appreciated

Thanks Andy

[Andygoodbloke]

After doing more research I have been led to believe that the fuel tank sender must "match" the gauge on the dash, if it doesn't then it will either not work or give weird readings like running from over full down to half when empty.

How do you tell if it is a match or not? Obviously if it works correctly it is correct, but If it doesn't work how do I Identify the sender is correct or not? I have been led to believe if you measure the resistance of the gauge the correct gauge for a Seirra / Samurai SJ50 should measure 0 to 90 ohms when full? what are the other readings of the incorrect senders?
Is there a serial number or another way to check?
The issue with the fuel sender/ gauge I am having, it seems logical to check everything starting at the tank - It is a replacement tank so have a feeling this maybe the issue, if it is the correct sender then the wiring will be examined.
Any suggestions please
Cheers Andy

[Gwagensteve]

Your issue is (I think) you don’t have a factory service manual, which explains the circuit, how to troubleshoot it, and what “normal” resistance is.

I don’t have my FSM handy but that’s going to be the key.

[Andygoodbloke]

Thanks Steve but what is a "FSM" is it a full service manual?
Where would I get one?

Thanks Andy

[Brenno]

Factory service manual

[Jezzer]

I can’t help with how to check them. But I can tell you. I tried one of the new ones off eBay from India (came with a new fuel tank) and it didn’t work. From memory a full tank only showed it to be a 1/4 tank on the gauge.
I dropped the tank and put the original back in and it seems to be operating accurately.


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[Andygoodbloke]

Thanks all for responding.
I have come up with a plan. Drop the tank and replace the sender in tank with the one which was in the bits box amounst radiator hoses, spare door handles and indicator lenses and other stuff I would regret if I threw it out, hopefully it is the original one

I did pass the multi meter across the old sender from the bits box, it didn't suggest there was anything apart from no connection. I proceeded to take the thing apart and found the metal arm which is meant to rub against a coil of copper for a reading was not touching. After bending I re tested the resistance and got readings at different spots from 0 to 110 ohms on a screw hole to the positive terminal. If I tested from either side of the coil it would read about 27 to 90 from empty to full
Next step is to get the tank back out and check if the resistance is anything like this one. before replacing if needing replacement.

Next step will be to try it with the gauge on the dash. - thanks Jezzer

[Andygoodbloke]

After testing I found it worked and got a reading so the next job will be to replace the sender unit in the tank this one. I was happy It was the first time the fuel gauge said anything which wasn't below empty in the off shut down position.

[Andygoodbloke]

After replacing the fuel sender and the bolts holding the unit as the last monkey rounded every screw off on the M5 bolts with either a posi or JIS I also added an additional earth wire from one of the bolts holding the sender to a good earth point. I tried the sender and got a signal/reading at the dash.
The down side is the sender is saying the tank is half full and can say there is not half a tank in there since I lifted it down and back in, I would guess a 1/4 at the most or even less.

any suggestions now as an unreliable gauge is just as bad as no gauge.

I have not driven the thing far enough yet to work out how much fuels gets you so far and Don't just want to fill it up just to see the gauge position
I do not know if the replaced tank in place is the same as the original or if it has increased volume
- how many litres is a standard tank?
- If it was a bigger tank I would think it would under read rather than over read
Thanks Andy

[Gwagensteve]

Stock tank is 40 litres.
Empty on the gauge generally leaves about 7 litres in the tank

[fordem]

Andygoodbloke wrote:

- If it was a bigger tank I would think it would under read rather than over read
Thanks Andy

This would depend on the design of the tank and the design of the sender - so to speak, whether the sender is "matched" to the tank - the sender doesn't know (or care) what the size (capacity) of the tank is, it just measures the level of fuel (float) - low (empty), half (half), high (full).

As an example, the "new Gen 4 Jimny" comes with a 40 liter tank, Long Ranger does an 80 liter replacement and supplies it with a new float arm that adapts the OEM sender to match the increased height of the replacement tank allowing the gauge to indicate the fuel level correctly.

Problems arise when people try to "mix'n'match" without a clear understanding of how the pieces interact - your "reading inaccuracy" could be either the gauge sender not right for the tank, or not right for the gauge, it could also be a problem with the sender, the gauge or the wiring.

If you remove the sender from the tank and move the float arm by hand, can you get the gauge to indicate both a full & an empty tank?

[Andygoodbloke]

Thanks Foredom and Steve
Can you purchase a required set being the dash gauge and sender to match - if so please advise me where to get them otherwise it will be a mix-match.

I added fuel to the tank and the fuel was a 10l tin then with idling and running to check wiring I would guess 7-8 litres - so be Steve's reckoning it should read empty or close to it.

I have just stuck the thing in yesterday and did not measure the full and empty positions - I was just happy to get a signal - but I may have to follow your advice and remove the tank again and not rush the testing.

Please advise where you can get both the gauge for the dash and the sender to match without going for an external additional gauge unless I have to.

Thanks Andy

[Gwagensteve]

I'm not really sure how to answer that. They're "matched" inherently because the stock sender and stock gauge work as a set.

Here is the troubleshooting section of the FSM for the circuit and the sender.



That's everything you should need to determine which bit isn't working properly.

[Andygoodbloke]

Thank you so much Steve

I now have something to say what it should be.

You and I may not agree on a few things, such as K&N filters, but I appreciate the information provided.

Cheers Andy