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Fuel Gauge showing wrong level


Paul H
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Hi, my fuel gauge is at 75% when full in my Vitesse . Looking to correct this if possible . I have another 2 spare petrol gauges . How can I check if it’s the sender or the guage . The voltage stabiliser is a solid state version . 

Previously I had issues when the needle slowly dropped to zero and climbed back after 10 mins or so . A bit disconcerting when this happened first time 😱.

When it was working it was accurate . Changed to solid state stabiliser and the zeroing stopped but with 25% error 

Paul 

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Has this always been the case? Mine ran at full, and the temp gauge at half way, for many years but last summer took a sudden and dramatic lurch to the left as I drove along, so that the fuel tank now reads about 75%, and the temp gauge points to a third, not half. I suspect the stabiliser, which is solid state from the early 2000s, but as the car is running well enough I just left it as is.

Does the gauge stay at 3/4 for a long time then start to move, or does it start to lower quite soon, but stay at the bottom for a long time without running out? (Carry a can of fuel just in case!)

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22 hours ago, johny said:

Not a problem with the float not moving far enough is it? First I would take it out and manually move it to the full position to see if you can get the correct reading...

Didn’t fancy siphoning the fuel , hoping there are further tests before dropping the fuel

Paul 

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21 hours ago, NonMember said:

Try shorting the sender to earth. If the gauge climbs past the full mark then it's a sender problem. If it only reaches 7/8 then suspect the stabiliser or the gauge.

Is there a way of testing the gauge ?

Paul

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25 minutes ago, Chris A said:

Am I missing something obvious? To check the stabiliser just put a voltmeter across it, the reading should be 10v surely?

I await to be corrected by my betters 🙊

I think that means having to remove the gauges to access it... so maybe a few other options to test in situ might be easier / lazier / my sort of thing.

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1 hour ago, Chris A said:

Am I missing something obvious? To check the stabiliser just put a voltmeter across it, the reading should be 10v surely?

I await to be corrected by my betters 🙊

Not across the stabiliser but across earth and the output of the stabiliser or the incoming connections onto either gauge. Obviously when doing this the senders should all be connected normally...

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2 hours ago, Chris A said:

To check the stabiliser just put a voltmeter across it, the reading should be 10v surely?

The output of the stabiliser, relative to earth, will be 10V if it's a modern solid state type. If it's an original bimetallic one then it's chopped 0-12-0-12 and it's very hard to tell whether it's right.

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Shouldn’t the voltage with the wire removed at the sender be stabilised ie 10volt as the fuel gauge is fed first then earthed at the sender.

just read N-M comment re bi-metallic stabiliser but didn’t I read at beginning it’s a solid state replacement stabiliser.

My Sprint had inconsistent gauge readings when the float was holed not empty but sometimes 3/4 or even 1/4 full bounced all over within minutes the float was not full of petrol when removed, cause was the wire arm to the float was sharp where it had been snipped in manufacture and over 40 years wore thro the float.

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I was driving along the A5 when the fuel gauge suddenly fell to empty event though I knew the tank was nearly full.  A little while later the gauge started to read again and worked perfectly from half full to nearly empty when I refilled.  The problem was that the resistive element in the sender had worn down so no longer made contact over the sector 1/2 to 3/4 full. Presumably previous owners had kept the fuel mainly in this range so it suffered the most wear as the fuel slopped about  as the car drove over bumps.  Replaced the sender but now it only read 3/4 full even when the tank was nearly overflowing.  Eventually diverted the wiring from the solid state 10V regulator so as the gauge was supplied with 12V and now it is fairly accurate although as yet I have never tested it to see what it reads as I run out of petrol! The temperature gauge continues to operate from the 10V supply.  So perhaps a replacement sender in your car has been calibrated to run from a 12V supply as the person placing the manufacturing contract failed to explain  the correct operating environment to the Asian factory.

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Yes I think that could be the problem. Perhaps you could get the level down below the sender hole, remove it and replace the float with something the same size that doesnt float. Then reinstall the sender and check you gauge reading, if not showing empty keep bending the float wire until it does. Even if the full reading doesnt end up perfect at least the most important one will be correct....

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Hi just setting testing the 3 fuel gauges I have to see if that is the weak link . I found a spare stabiliser , the one on the Vitesse is a digital version . The voltage out put from the mechanical stabiliser was pulsing from  5 to 10 ish , difficult to read as pulsing was fast . Is this what should be happening . With the stabilised voltage I can test the 3 gauges to see if this is the issue   On the pic one of the terminals is painted red , I’ve assumed this is positive input or doesn’t it matter ? 
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Paul 

 

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3 minutes ago, Pete Lewis said:

as marked on the face     B is battery    I is instruments    

the case must be earthed 

you will have fun getting the vice behind the dash  !!!!!   

Pete

Thanks Pete didn’t see the B and I 😱

Paul 

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