GT6 fuel gauge and sender issues

[Dave the tram]

I know there have been many threads on this topic but just wanted other opinions on my specific problem.

- The fuel gauge reads just over half when full then seems to drop proportionally. It's been like this for a long time but I THINK it used to read full years ago, just didnt't fill it right up very often back then.

- The temperature gauge works correctly and shows halfway or just over when hot, goes higher of stood in traffic fir a long time when hot, so it can go higher.

- If I take the lead off the fuel sender unit and short it to earth, the gauge reads full. Am I correct in thinking this means that that the balance resistor is ok (I've already swapped to a new one anyway with no difference) and that the sender is faulty?

- I've taken the sender out and everything looks ok and the float works with no leaks.

- If I move the arm on the sender across its full range, out of the tank, while earthing it, the gauge ranges from empty to half. I blocked the tank opening very well for safety before reconnecting the battery to try this! I might try this again in steps across the range, leaving time for the gauge to settle for each position

But I think this already shows I need a new sender unit. Although the car is a fairly original late Mk 3, the sender looks like an earlier one, no pipes or breathers, just the arm and float etc. and 2 terminals. It has the lock ring fitting and the seal still looks good.

Has anyone bought a similar replacement recently that does the job? Rimmers lists one for earlier GT6s that I could try, that looks more or less the same as mine (as well as a different looking one specified for the Mk 3) but can't find any others.

Cheers

Dave

 

[AidanT]

Dave 

I had the exact same symptoms and changed the sender which can cause this but it made no difference to me

If I was to do it again, I would change the voltage stabilizer first as not only did it solve my problem it was also by far the cheapest part!

Aidan

 

[Pete Lewis]

In general if  the voltage stabiliser fails and gives out 12+volts instead of a steady 10.5v the gauges will read higher than they should

If you have a non stabilised gauge sender in a stabilised system  , fuel or temp  you will get some very odd results

They  cannot be mixed up

Ifnthe temp gauge reads about half but climbs a bit in traffic or whatever expect it to read a little more  this is about right .

Of you only get a half reading when moving the arm to full but  do get a full reading when shorting then its certainly points to a duff float sender.

All stabilised gauge  floats use the same resistance just the float arm changes to suit tank designs

Do check the float earth is earthing ok , 

Pete

[Dave the tram]

Well looks like I'm on a roll here, having fixed the steering and the gear linkages, I now discover that fuel sender units are maintainable! With nothing to lose if I need to buy a new one anyway, folded back the 3 metal tabs on the unit and lifted off the cover, cleaned the windings with a toothbrush and a dab of cellulose thinners, cleaned the contactor and bent it a bit to increase spring pressure and put it back together. Tested it out of the tank and, hey presto, works perfectly and reads accurately over the full range. 60 quid saved.

Cheers

Dave

[Ian Faulds]

Well done great job

[Pete Lewis]

Never underestimate the power of ....look see...

 

Brilliant 

Pete

[Bigfella70]

Great result and very satisfying to trace and repair the issue. I did similar once on a Jag XJC where the twin tanks had been plumbed in incorrectly and only one tank reading on the gauge. I'd also bet your original unit is far better quality than any available replacements these days!