15 replies to this topic

[mkw]

Hello, 

 

I've had a problem recently with the above.

 

The details are centre binnacle speedo, other gauges work fine. The fuel gauge reads correct when the car is stood, full-empty and everything in between but drops to around a 1/4 when driving.

 

I've checked the earth on the sender unit, nice and clean and tight. I've bridged the wires and the gauge shoots up to full. I've lifted the float and there is no fuel stuck in there so that seems ok.

 

I noticed when i went for a drive yesterday at one point the rev counter dropped to 0 for a split second then didn't have any issues again after that, i don't think it's related but thought i'd mention it.

 

The car is 1991, 998cc.

 

I'm a bit stumped, if the temp gauge was iffy as well i'd think voltage stabiliser or something like that.

 

Any ideas?

[andyapanel]

My Grandfather's Allegro did that.

The cause was the middle of the sender was being wiped too much, wearing it out.

Why? Because he was too "careful" to ever put a full tank in, and he maintained that as half a tank weighed less than a full one, he improved his fuel economy.

When I inherited it, I had to remember when the fuel gauge dropped to zero, whether it WAS zero, or just halfway.

Good luck sorting it out.

Edited by andyapanel, 27 August 2019 - 02:56 PM.

[mkw]

Do you think changing the sender would do anything? I’ve got another car I could take it off and swap round when the fuel is low enough to remove. Is it worth a try or just wasting time?

[cal844]

You could always drain the tank and just leave a small amount of fuel in there, changing a sender is very easy.

I have swapped a sender with a used spare(you can check that the 'New' sender works by hooking the wiring and manually operate it) the hardest part was getting the sealing ring tight enough as the 'ramp angle is fairly steep and short, so you can bend the lock tabs on the ring.

Take care and don't be silly when doing this task

Edited by cal844, 31 August 2019 - 01:28 PM.

[mkw]

I'm bringing back an old thread but I've been making do with the dodgy gauge for a bit.

 

Finally got around to changing the fuel sender unit but it is still the same, you can manually operate the sender and gauge appears to respond (although slowly) but when driving the fuel level drops again.

 

The temp gauge in the centre binnacle works fine so I can't imagine that its the voltage stabiliser, or is that possible?

[mkw]

Still on going issues with this, i'm wondering now whether to change to a solid state voltage stabiliser to see if that helps it and also for reliability long term.

 

If this doesn't work is it likely that the fuel gauge is faulty? Is it common for these to go? I didn't think there was much to them really.

 

I have done the various resistance tests listed on other posts, changed the sender, re-earthed the voltage stabiliser and traced other earths along the way - still the temp gauge works fine! :S

[sonscar]

Is the temp guage electric?Could be the voltage regulator as the car voltage could be higher when driving,Would this make it read high or low?Ido not know but the regulator may be a easy fix.Steve..

[mkw]

Is the temp guage electric?Could be the voltage regulator as the car voltage could be higher when driving,Would this make it read high or low?Ido not know but the regulator may be a easy fix.Steve..

Yes the temp gauge is electric, it’s the old smiths 52mm gauge which requires 10v from the stabiliser.

I replaced the stabiliser for a solid state one, tested and 12v goes in 10v comes out. Filled with fuel and went for a drive but still have the gauge dropping to 1/4 full when driving so I have no idea now! 🙁

[Quinlan minor]

It'd be a bit of a fiddle but, since you've tried so many things (my money was on the sender, as I'd had similar: dropped to below a 1/4 when it still had about half a tank), fit a resistor of an appropriate value (eg. 1/2 tank resistance as measured from the sender) to the sender end of the wiring. Test drive. If you get the same symptoms, disconnect wire from the gauge and connect the resistor there. Test drive. That should rule out any problem with the wiring between the sender and the guage.

Good luck!

Edited by Quinlan minor, 04 December 2020 - 08:26 PM.

[Spider]

As well as that suggested by Quinlan above, connect a meter to the Sabaliser Output and check the voltage there while you drive.

[cal844]

I agree with a 'live' voltage check whilst in use. Could it possibly be the floats too?

[Dnaryam]

Bringing thie topic back up, as i have the exact saame problem with both fuel and temp, and the stabilizer is working perfectly with constant 10v output. Have you ever solved your problem?

[mkw]

I’ve never fully cured the problem, I bought a Spiyda Gauge Matcher and that seemed to help but not fully solve the issue. If you end up fixing the issue, let me know!

[Spider]

If I can suggest, check the Earth on the Voltage Stabaliser.

[mkw]

I checked mine, re-ran a new one just in case and replaced the stabiliser and sender.