Gas - Petrol - Fuel GUAGE reads full

[PM7]

Hi everyone does anyone have any ideas about these?

After a winter lay up my fuel gauge reads full all the time, i have cleaned the contacts at the sender end but nothing changed.


Many thanks Patrick.
1981 TR7 DHC
1980 TR7 Premiun x2

[jclay (RIP 2018)]

Either the gauge is stuck (Probably not!), the sender is stuck, (try disconnecting the wires at the sender and turning on the power), the tank has filled up with water,

Or there is a short in the Green/Black wire from the sender. Also, the Printed circuit board on the back of the instrument pod has been rubbing on something and the fuel gauge circuit shorted to ground.

Disconnect the Green/Black wire from the sender and turn on the power. If the gauge reads full, there is a short.

Remove the [url="http://web.me.com/jclaythompson/Technical/Replacing_Tech.html"]facia from the instrument pod[/url], loosen the screws and pull the pod out about an inch. Turn on the power. If it reads full, then the wire is probably the culprit, if the gauge functions normally, the the circuit board is suspect.

Clay

[url="http://web.mac.com/jclaythompson/Site/Welcome.html"]My Triumph Site[/url], [url="http://web.me.com/jclaythompson/Technical"]Technical Stuff[/url], [url="https://docs.google.com/?hl=en&tab=wo&authuser=0&pli=1#all"]Download Page[/url], [url="https://public.me.com/jclaythompson"]My Public Folder[/url], [url="http://web.me.com/jclaythompson/tr8/Welcome.html"]My TR8 Site[/url]

[PM7]

Many thanks Clay i will give it a go at weekend also i forgot to mention that the low fuel indicator light still works, and at the right time.

Patrick.
1981 TR7 DHC
1980 TR7 Premiun x2

[jclay (RIP 2018)]

Then the sender is not stuck. The Float Lever sets on a metal rest when the tank gets close to empty, completing a circuit, which sends current to the delay unit mounted above the instrument pod, then to the low fuel light.

So, it's either a shorted wire, shorted printed circuit board. Does the gauge go down when the power is off? If so, then it is in the wire from the sender.

Clay

[PM7]

Hi Clay, yes the guage goes up and down when power on and off, must be that wire then!


Many thanks Patrick.
1981 TR7 DHC
1980 TR7 Premiun x2

[jclay (RIP 2018)]

Patrick,

The first place I would check is under the car, right where the rear bulkhead meets the drive shaft tunnel. There is a metal cover held on by two bolts that protects the wires from the drive shaft.

If not there, pull the console storage box and lift the carpet, the wires going to the fuel gauge are right on top.

Clay

[url="http://web.mac.com/jclaythompson/Site/Welcome.html"]My Triumph Site[/url], [url="http://web.me.com/jclaythompson/Technical"]Technical Stuff[/url], [url="https://docs.google.com/?hl=en&tab=wo&authuser=0&pli=1#all"]Download Page[/url], [url="https://public.me.com/jclaythompson"]My Public Folder[/url], [url="http://web.me.com/jclaythompson/tr8/Welcome.html"]My TR8 Site[/url]

[PM7]

Hi Clay,

thanks for all the info, i will hopefully sort this out now.

Many thanks Patrick.
1981 TR7 DHC
1980 TR7 Premiun x2

[nervousnewowner]

still got that job to do on mine,,,lol, been redoing the wiring from the back to the front, just got as far as the seats so fuel guage next, bought a second hand binnacle off ebay, picking it up on weekend, and replaced the unit in the tank about two yrs ago....mine reads full and goes down ..... i think..... when power off so wiring will get replaced in next weekend or two....


the project at birth, watch it evolve...I hope...

[PM7]

...Yea i think im going to have further electrical issues with my 1981 DHC, when you dig into the wiring it looks like every man and his dog has had a go!!!
But on the other hand the last premium i bought,(which had been stored for 15 years)is like when you lift the carpet the last man that was there was at the factory. Awesome!!

Patrick.
1981 TR7 DHC
1980 TR7 Premiun x2

[martin rowsell]

Hi, i have the same problem, guage reads full when turned on and empty when off! idisconected the green and black wire and it reads empty when switched on, would you suggest a faulty sender? it is only 2 years old, so thinking it couldn't be faulty i changed the guage but to no avail, look forward to your comments,
Martin

[jclay (RIP 2018)]

Sender is either stuck in the up position or has a short to ground. Replace the sender.

Clay

[url="http://web.me.com/jclaythompson/Site/Welcome.html"]My Triumph Site[/url], [url="http://web.me.com/jclaythompson/Technical"]Technical Stuff[/url], [url="https://public.me.com/jclaythompson"]My Public Folder[/url], [url="http://web.me.com/jclaythompson/tr8/Welcome.html"]My TR8 Site[/url]

[martin rowsell]

Thanks, thats what i thought but wanted someone else's opinion before i ended up drenched ip the flamable stuff!!
Cheers,
Martin.

[martin rowsell]

Help!! replaced sender, replaced guage,ran new wires to the pod, still reads full when the power is on,
any suggestions appreciated!!
Martin

[FI Spyder]

With the sender out, if you move the arm the resistance between ground and fuel gauge tab will vary. This can be measured by an ohmmeter. The voltage to the gauge will correspondingly change varying the needle position. If the supply wire was shorting out you would have no/little needle movement. I suspect there has been some wire bodging done where the gauge is getting a constant 12 volts rather than the variable voltage from the sender. Running a test wire directly from the sender to the hot terminal on the gauge will confirm this. It won't tell you where the problem is though, only a tracing of the wire from sender to the gauge will reveal what has really happened. Alternately just disconnect the current hot wire from the gauge and connect the new wire and forever entomb another wiring bodge to what has been done before. It will work but not recommended (by me anyway).


TR7 Spider - 1978 Spitfire - 1976 Spitfire - 1988 Tercel 4X4 - Kali on Integra - 1991 Integra - Yellow TCT

[martin rowsell]

Hi F1 Spyder, Thanks for your input, i have tried the sender and i get varying voltage and resistance, the wires dont seem to be shorted out, i also get varying voltage at the guage end, i have also removed the guage and sender and wired them up on the bench but still no luck!! i have 2 gauges and both do the same, ifind it hard to belive that both are shot! the origonal one that was in the car worked fine untll a winter lay up then when i went to get her ready for the road again it just decided i had a full tank (if only)any other ideas?
Martin.