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Club Triumph forum - Cars - TR7-8 - TR7 V8 - Fuel gauge not working
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"Stuart Wilson"
posts: 810
Pendle & Pennine group
joined on Wed 9th Nov 2011
 posted Wed 8th Jan 2014

The fuel gauge on my 7 doesn't work. I don't think it's teh sender unit as I got a new one and tried the wires on it and was just the same. I'm thinking it maybe the actual gauge.

Does anyone have any ideas before I pull the dash to bits

cheers

1982 TR7 FHC "Sprint"
Moss Roadster - upgrade now in progress
1985 Yamaha FZ750
1997 Vauxhall Calibra 2.5 V6 in need of a little TLC -- looking to sell it
2000 Porsche Boxster S -- mid life crisis?  
2004 Skoda Superb 1.9TDI 130 Auto
Vauxhall Nova 1.6 16v stage rally car - NOW SOLD
1988 Vauxhall Nova 1.2 merit NOW SOLD
You can never have too many toys!!
2012 RBRR  TR7 "Sprint" car 16 (completed)
2014 RBRR Moss Roadster car 72 (retired)
2016 RBRR Moss Roadster TR7 "Sprint" car 123 (completed)
2018 RBRR Moss or TR7 --- choices
Tags - TR7 TR7 Sprint TR7 V8 TR8
"LED Brown"
posts: 39
non member
 posted Wed 8th Jan 2014 reply 1 of 21

Could be the voltage stabiliser. It's mounted on the back of the speedo. On other cars this also feeds the temperature gauge, not sure about the 7 though.
Tags - TR7 TR7 Sprint TR7 V8 TR8
"LED Brown"
posts: 39
non member
 posted Wed 8th Jan 2014 reply 2 of 21

Not sure I got that right! I might have ment the low fuel warning relay
Tags - TR7 TR7 Sprint TR7 V8 TR8
"Beans"
posts: 5734
Netherlands
joined on Sun 5th Mar 2006
 posted Wed 8th Jan 2014 reply 3 of 21

From another forum, maybe this might help ...

Quote:
... decided to check out gauge and sender unit wired on the bench. readings as follows.
DC Power supply set at 13.9 Volts
Gauge reading full ...... 0.53 to 0.63 Volts
Gauge reading 3/4 ...... 2.71 to 2.75 Volts
Gauge reading 1/2 ...... 3.95 to 4.02 Volts
Gauge reading 1/4 ...... 4.88 to 4.97 Volts
Gauge reading Empty ..... 5.49 to 5.05 Volts
Variation read and recorded after many checks. hence the slight variations.
Full tank read 10 Ohms
Empty tank read 312 Ohms
Of course different gauges will vary slightly as will the variable resistor in the sender unit so figures for reference only.
All test carried out using calibrated test equipment so my figures can be trusted.
Just hope this will help someone in the future.
...


So easy to check the sender is indeed functioning properly (never take anything for granted)
Also check wiring for damage resulting in a short circuit somewhere.
And last check the low fuel delay unit mounted to the stop of the instrument binnacle.

The gauge itself seldom fails unless you have been welding on the car with electrics connected one way or another.

1976 TR7 FHC (currently undergoing some TLC ...)
1980 TR7 DHC (a.k.a. Kermette, my first car bought in 1988 )
1981 TR7 FHC (Sprint engined, a.k.a. 't Kreng)
http://tr7beans.blogspot.com/
Tags - TR7 TR7 Sprint TR7 V8 TR8
"Stuart Wilson"
posts: 810
Pendle & Pennine group
joined on Wed 9th Nov 2011
 posted Thu 9th Jan 2014 reply 4 of 21

Thanks for that, it will give me something to do on sunday

1982 TR7 FHC "Sprint"
Moss Roadster - upgrade now in progress
1985 Yamaha FZ750
1997 Vauxhall Calibra 2.5 V6 in need of a little TLC -- looking to sell it
2000 Porsche Boxster S -- mid life crisis?  
2004 Skoda Superb 1.9TDI 130 Auto
Vauxhall Nova 1.6 16v stage rally car - NOW SOLD
1988 Vauxhall Nova 1.2 merit NOW SOLD
You can never have too many toys!!
2012 RBRR  TR7 "Sprint" car 16 (completed)
2014 RBRR Moss Roadster car 72 (retired)
2016 RBRR Moss Roadster TR7 "Sprint" car 123 (completed)
2018 RBRR Moss or TR7 --- choices
Tags - TR7 TR7 Sprint TR7 V8 TR8
"Toledo Man"
posts: 2941
non member
 posted Thu 9th Jan 2014 reply 5 of 21

Try earthing the wire that's attached to the sender. If the gauge is working it will go all the way to the full mark. An easy way of testing the gauge.

Toledo Man

HCR 2006 & 2007 finisher
1972 Dolomite 1850 auto (NYE 751L - The rolling restoration), 2008 Citroën C4 Grand Picasso 2.0 HDi Exclusive (MA08 WCL - the modern), 1995 BMW 318i (M265 PNC - Project Bimmer), 1991 Toyota Celica GT (J481 ONB - the current project car)

Former stable of 5 Acclaims, 1 Toledo, 2 1500fwd, 1 1300fwd, 1 Dolomite 1300 & 1 Dolomite Sprint (that's just the Triumphs!)
I've still got some parts for sale...
Check out my Blog on http://triumphtoledo.blogspot.com/

"Think for yourself. Question authority." - Timothy Leary (1920-1996)
Tags - TR7 TR7 Sprint TR7 V8 TR8
"Beans"
posts: 5734
Netherlands
joined on Sun 5th Mar 2006
 posted Fri 10th Jan 2014 reply 6 of 21

Toledo_Man wrote:
Try earthing the wire that's attached to the sender. If the gauge is working it will go all the way to the full mark. An easy way of testing the gauge.

That indeed is much easier, but with a TR7 you do need an assistant as the connectors are underneath the car.

1976 TR7 FHC (currently undergoing some TLC ...)
1980 TR7 DHC (a.k.a. Kermette, my first car bought in 1988 )
1981 TR7 FHC (Sprint engined, a.k.a. 't Kreng)
http://tr7beans.blogspot.com/
Tags - TR7 TR7 Sprint TR7 V8 TR8
"Stuart Wilson"
posts: 810
Pendle & Pennine group
joined on Wed 9th Nov 2011
 posted Fri 10th Jan 2014 reply 7 of 21

If I manage to motivate myself on sunday to get in the garage I'll try the above, and report back

1982 TR7 FHC "Sprint"
Moss Roadster - upgrade now in progress
1985 Yamaha FZ750
1997 Vauxhall Calibra 2.5 V6 in need of a little TLC -- looking to sell it
2000 Porsche Boxster S -- mid life crisis?  
2004 Skoda Superb 1.9TDI 130 Auto
Vauxhall Nova 1.6 16v stage rally car - NOW SOLD
1988 Vauxhall Nova 1.2 merit NOW SOLD
You can never have too many toys!!
2012 RBRR  TR7 "Sprint" car 16 (completed)
2014 RBRR Moss Roadster car 72 (retired)
2016 RBRR Moss Roadster TR7 "Sprint" car 123 (completed)
2018 RBRR Moss or TR7 --- choices
Tags - TR7 TR7 Sprint TR7 V8 TR8
"Stuart Wilson"
posts: 810
Pendle & Pennine group
joined on Wed 9th Nov 2011
 posted Mon 13th Jan 2014 reply 8 of 21

well I chickened out on sunday, it was too cold or I'm getting soft. So nothing done to any of my cars

1982 TR7 FHC "Sprint"
Moss Roadster - upgrade now in progress
1985 Yamaha FZ750
1997 Vauxhall Calibra 2.5 V6 in need of a little TLC -- looking to sell it
2000 Porsche Boxster S -- mid life crisis?  
2004 Skoda Superb 1.9TDI 130 Auto
Vauxhall Nova 1.6 16v stage rally car - NOW SOLD
1988 Vauxhall Nova 1.2 merit NOW SOLD
You can never have too many toys!!
2012 RBRR  TR7 "Sprint" car 16 (completed)
2014 RBRR Moss Roadster car 72 (retired)
2016 RBRR Moss Roadster TR7 "Sprint" car 123 (completed)
2018 RBRR Moss or TR7 --- choices
Tags - TR7 TR7 Sprint TR7 V8 TR8
"tim_trinda"
posts: 79
non member
 posted Tue 14th Jan 2014 reply 9 of 21

My non-working gauge was simply a corroded connector at the sender end.

The sender also has a separate ground connection ... check that too.

If you have a digital multi-meter check the voltage (not sure what it should be ~12V?) on the wire coming from the gauge at the sender end ... if it reads zero then you have an dodgy connection between the gauge and sender.

Another gotcha is the gauges are held in with weird security type screws (well mine are) ... I had to grind a hollow on a flat bladed screwdriver to get them out.

Good luck!
Tags - TR7 TR7 Sprint TR7 V8 TR8
"Stuart Wilson"
posts: 810
Pendle & Pennine group
joined on Wed 9th Nov 2011
 posted Sat 18th Jan 2014 reply 10 of 21

Update........

silly me, the gauge is actually reading full all the time.

today I disconnected the green/black wire from the sender, gauge went to empty. Disconnected the wire from the multiplug on the back of the dash, then connected a length if wire from the sender to the gauge. Exactly same result, gauge reading full. Got out the new sender I bought a while ago, connected that up postioned the float in the empty position.  Low level light comes on but gauge still reads full, this is with both the original car wire or my length of wire.

This makes me think it is the actual gauge at fault.

Any thoughts on this???

1982 TR7 FHC "Sprint"
Moss Roadster - upgrade now in progress
1985 Yamaha FZ750
1997 Vauxhall Calibra 2.5 V6 in need of a little TLC -- looking to sell it
2000 Porsche Boxster S -- mid life crisis?  
2004 Skoda Superb 1.9TDI 130 Auto
Vauxhall Nova 1.6 16v stage rally car - NOW SOLD
1988 Vauxhall Nova 1.2 merit NOW SOLD
You can never have too many toys!!
2012 RBRR  TR7 "Sprint" car 16 (completed)
2014 RBRR Moss Roadster car 72 (retired)
2016 RBRR Moss Roadster TR7 "Sprint" car 123 (completed)
2018 RBRR Moss or TR7 --- choices
Tags - TR7 TR7 Sprint TR7 V8 TR8
"AnthonyF"
posts: 9
Southern group
joined on Thu 23rd Feb 2006
 posted Sat 18th Jan 2014 reply 11 of 21

Stuart, the green/black wire carries power FROM the gauge to the sender unit in the tank, the float arm operates a potentiometer. When the tank is full (= the float arm is at it's highest point) the potentiometer gives full earth to the current via the black wire & the gauge reads full. To test the gauge turn on the ignition, disconnect the green/black from the sender, the gauge should read empty (like yours does). Now touch green/black to a good earth & the gauge should swing to full. If it does not, or only moves part way, then the gauge is faulty.

Having tested the green/black wire, normally I would suspect the sender arm to be stuck or the potentiometer faulty however your experiment today with a replacement sender does suggest that the gauge is faulty. I think you are going to have to try a replacement gauge.
Tags - TR7 TR7 Sprint TR7 V8 TR8
"Stuart Wilson"
posts: 810
Pendle & Pennine group
joined on Wed 9th Nov 2011
 posted Sun 19th Jan 2014 reply 12 of 21

Are gauges still available or will I need to be looking for a 2nd hand gauge or dash?

1982 TR7 FHC "Sprint"
Moss Roadster - upgrade now in progress
1985 Yamaha FZ750
1997 Vauxhall Calibra 2.5 V6 in need of a little TLC -- looking to sell it
2000 Porsche Boxster S -- mid life crisis?  
2004 Skoda Superb 1.9TDI 130 Auto
Vauxhall Nova 1.6 16v stage rally car - NOW SOLD
1988 Vauxhall Nova 1.2 merit NOW SOLD
You can never have too many toys!!
2012 RBRR  TR7 "Sprint" car 16 (completed)
2014 RBRR Moss Roadster car 72 (retired)
2016 RBRR Moss Roadster TR7 "Sprint" car 123 (completed)
2018 RBRR Moss or TR7 --- choices
Tags - TR7 TR7 Sprint TR7 V8 TR8
"Stuart Wilson"
posts: 810
Pendle & Pennine group
joined on Wed 9th Nov 2011
 posted Sun 19th Jan 2014 reply 13 of 21

Just checked Rimmer site, gauge no longer available.  Looks like a phone call to S & S this next week, see if they can help out.

1982 TR7 FHC "Sprint"
Moss Roadster - upgrade now in progress
1985 Yamaha FZ750
1997 Vauxhall Calibra 2.5 V6 in need of a little TLC -- looking to sell it
2000 Porsche Boxster S -- mid life crisis?  
2004 Skoda Superb 1.9TDI 130 Auto
Vauxhall Nova 1.6 16v stage rally car - NOW SOLD
1988 Vauxhall Nova 1.2 merit NOW SOLD
You can never have too many toys!!
2012 RBRR  TR7 "Sprint" car 16 (completed)
2014 RBRR Moss Roadster car 72 (retired)
2016 RBRR Moss Roadster TR7 "Sprint" car 123 (completed)
2018 RBRR Moss or TR7 --- choices
Tags - TR7 TR7 Sprint TR7 V8 TR8
"Beans"
posts: 5734
Netherlands
joined on Sun 5th Mar 2006
 posted Sun 19th Jan 2014 reply 14 of 21

4576 wrote:
... silly me, the gauge is actually reading full all the time ...

Did you disconnect all wiring when you bypassed the wiring loom?
That fact that he gauge is working sort of would lead me to think there's a wiring short.

1976 TR7 FHC (currently undergoing some TLC ...)
1980 TR7 DHC (a.k.a. Kermette, my first car bought in 1988 )
1981 TR7 FHC (Sprint engined, a.k.a. 't Kreng)
http://tr7beans.blogspot.com/
Tags - TR7 TR7 Sprint TR7 V8 TR8
"Stuart Wilson"
posts: 810
Pendle & Pennine group
joined on Wed 9th Nov 2011
 posted Sun 19th Jan 2014 reply 15 of 21

Only disconnected the green/black as that is the one between gauge and sender and replaced, fault the same. The earth and low level light wiring left on and warning light working correctly, so the earth wire and green/orange wire ok.So to me points to the gauge.
I'll have to bring my multi meter home from work to double check.

1982 TR7 FHC "Sprint"
Moss Roadster - upgrade now in progress
1985 Yamaha FZ750
1997 Vauxhall Calibra 2.5 V6 in need of a little TLC -- looking to sell it
2000 Porsche Boxster S -- mid life crisis?  
2004 Skoda Superb 1.9TDI 130 Auto
Vauxhall Nova 1.6 16v stage rally car - NOW SOLD
1988 Vauxhall Nova 1.2 merit NOW SOLD
You can never have too many toys!!
2012 RBRR  TR7 "Sprint" car 16 (completed)
2014 RBRR Moss Roadster car 72 (retired)
2016 RBRR Moss Roadster TR7 "Sprint" car 123 (completed)
2018 RBRR Moss or TR7 --- choices
Tags - TR7 TR7 Sprint TR7 V8 TR8
"AnthonyF"
posts: 9
Southern group
joined on Thu 23rd Feb 2006
 posted Tue 21st Jan 2014 reply 16 of 21

Yes I would try another gauge. A used one should not cost much - I bought a complete instrument panel for a few pounds just to have a spare set of gauges! AFAIK the fuel gauges are all the same except that late cars had the ISO fuel symbol on the gauge.

The gauge has 3 internal coils, with the magnetic bar through the middle having the dial indicator needle attached. Two of the coils have an almost constant current but the current to the third is varied by the tank sensor, thus making the magnet bar rotate & move the dial needle. If that 3rd coil is faulty it may simply register full current all the time making the gauge read full.
Tags - TR7 TR7 Sprint TR7 V8 TR8
"Stuart Wilson"
posts: 810
Pendle & Pennine group
joined on Wed 9th Nov 2011
 posted Wed 22nd Jan 2014 reply 17 of 21

Might have a 2nd hand gauge sorted. Someone is going to have a look and see what they have lying about. Hopefully it will sort it.

Thanks for all the help/advice so far

1982 TR7 FHC "Sprint"
Moss Roadster - upgrade now in progress
1985 Yamaha FZ750
1997 Vauxhall Calibra 2.5 V6 in need of a little TLC -- looking to sell it
2000 Porsche Boxster S -- mid life crisis?  
2004 Skoda Superb 1.9TDI 130 Auto
Vauxhall Nova 1.6 16v stage rally car - NOW SOLD
1988 Vauxhall Nova 1.2 merit NOW SOLD
You can never have too many toys!!
2012 RBRR  TR7 "Sprint" car 16 (completed)
2014 RBRR Moss Roadster car 72 (retired)
2016 RBRR Moss Roadster TR7 "Sprint" car 123 (completed)
2018 RBRR Moss or TR7 --- choices
Tags - TR7 TR7 Sprint TR7 V8 TR8
"Stuart Wilson"
posts: 810
Pendle & Pennine group
joined on Wed 9th Nov 2011
 posted Sun 15th Feb 2015 reply 18 of 21

I know it's been a while.
I've got round to doing some more with this.

I've connected a wire to a spare sender unit and direct to the plug on the clocks, disconnecting the loom wire, tried a separate earth. The fault was the same.

Then this morning I tried wiring up another gauge and sender, completely separate from the car. I got the same fault, gauge reading full.

So any ideas what could be wrong, or have I got another duff gauge?

1982 TR7 FHC "Sprint"
Moss Roadster - upgrade now in progress
1985 Yamaha FZ750
1997 Vauxhall Calibra 2.5 V6 in need of a little TLC -- looking to sell it
2000 Porsche Boxster S -- mid life crisis?  
2004 Skoda Superb 1.9TDI 130 Auto
Vauxhall Nova 1.6 16v stage rally car - NOW SOLD
1988 Vauxhall Nova 1.2 merit NOW SOLD
You can never have too many toys!!
2012 RBRR  TR7 "Sprint" car 16 (completed)
2014 RBRR Moss Roadster car 72 (retired)
2016 RBRR Moss Roadster TR7 "Sprint" car 123 (completed)
2018 RBRR Moss or TR7 --- choices
Tags - TR7 TR7 Sprint TR7 V8 TR8
"Beans"
posts: 5734
Netherlands
joined on Sun 5th Mar 2006
 posted Mon 16th Feb 2015 reply 19 of 21

Presuming you checked the sender is working properly ...
You sure you wired everything correctly  :-/

1976 TR7 FHC (currently undergoing some TLC ...)
1980 TR7 DHC (a.k.a. Kermette, my first car bought in 1988 )
1981 TR7 FHC (Sprint engined, a.k.a. 't Kreng)
http://tr7beans.blogspot.com/
Tags - TR7 TR7 Sprint TR7 V8 TR8
"Stuart Wilson"
posts: 810
Pendle & Pennine group
joined on Wed 9th Nov 2011
 posted Mon 16th Feb 2015 reply 20 of 21

Same result with the new sender in the tank, yes wired as it would be in the dash. Just have to do what I did on the RBRR in 2012, make sure I fill up every 200 miles or so

1982 TR7 FHC "Sprint"
Moss Roadster - upgrade now in progress
1985 Yamaha FZ750
1997 Vauxhall Calibra 2.5 V6 in need of a little TLC -- looking to sell it
2000 Porsche Boxster S -- mid life crisis?  
2004 Skoda Superb 1.9TDI 130 Auto
Vauxhall Nova 1.6 16v stage rally car - NOW SOLD
1988 Vauxhall Nova 1.2 merit NOW SOLD
You can never have too many toys!!
2012 RBRR  TR7 "Sprint" car 16 (completed)
2014 RBRR Moss Roadster car 72 (retired)
2016 RBRR Moss Roadster TR7 "Sprint" car 123 (completed)
2018 RBRR Moss or TR7 --- choices
Tags - TR7 TR7 Sprint TR7 V8 TR8
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