Fuel Gauge

[g4zur]

Hi All
I have read several posts on forum regarding the fuel gauge. I have a bit of a dilemma, Under inspection when gauge didn't work at all, I found broken wires to the tank sender unit. I replaced connections with new. Now the gauge is showing full all the time. Needle all the way over.
Could this be just the gauge itself? Or have I got a sender unit problem. 34 year old tank and worried about removing unit.
Any help would be much appreciated.
Regards
Gareth

G.P.Albrighton

[dursleyman]

Gareth, the fuel gauge in my project car had the same fault when I bought it so it always read full. The previous owner had already fitted a new tank unit to try and fix it so the wiring was suspected.
The wiring and connections all looked OK and tested fine to me when I put a "new" tank in but the fault stayed.
I changed the gauge yesterday and its now working perfectly.

Russ

1980 TR7 Sprint DHC
Dursley
UK

http://tr7russ.blogspot.co.uk/

[RJS]

Ordered a new sending unit for my car yesterday.

[FI Spyder]

With the fuel low, pull the sender unit. Put an ohm meter across the sender terminals (not the low fuel one) and measure the resistance as you physically move the lever. It should change the reading on the meter as you move it. If it changes smoothly your sender should be good. Not sure of the actual readings as I didn't record them. Not likely the sender as it would somehow have to have shorted out to cause full gauge. If it's not that it must be the gauge.





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

[g4zur]

Thanks for replies to all. Will try a new Gauge first I think. I understand the testing of the variable resistor on sender unit. Still worried about the locking ring removal on an old tank and re-sealing.
Hope its the same problem you had Russ, Trust you enjoyed the holiday in the sun Russ.
Regards
Gareth

G.P.Albrighton

[g4zur]

Russ did you remove dash to change gauge or from underneath.
Thanks
Gareth

G.P.Albrighton

[FI Spyder]

<blockquote id="quote"><font size="1" face="Century Gothic, Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by g4zur</i>

I understand the testing of the variable resistor on sender unit. Still worried about the locking ring removal on an old tank and re-sealing.
<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">

The trick is to tap it off with a punch by hitting it near the base of the tabs (3) so you don't bend them over. Same when you are tapping it back on.

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

[dursleyman]

<blockquote id="quote"><font size="1" face="Century Gothic, Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by g4zur</i>

Russ did you remove dash to change gauge or from underneath.
Thanks
Gareth

G.P.Albrighton
<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">

Gareth, you can do it without removing the instrument cluster but you need to remove clear screen and the mask to get access to the gauges.
You have to take off the drivers side top of the dash and the column shroud. There are several "hidden" screws so have a look at your manual to find them. When those are off there are three funny headed screws that hold the clear screen, the mask lifts out and the instruments are right there. A couple more of those funny screws hold the gauge which is just pushed in with three terminals.
I did it originaly to change the bulbs to LED's and then again to fit an oil pressure gauge in place of the clock and now just done the fuel gauge. It gets easier each time!

Russ

1980 TR7 Sprint DHC
Dursley
UK

http://tr7russ.blogspot.co.uk/

[g4zur]

Thanks again Russ. Bet if you whistle now your dash comes out lol.
Speedo cable change today, Fuel gauge next.
Regards
Gareth.

G.P.Albrighton

[g4zur]

While I was under the dash with head torch on replacing speed cable (thanks for the tip hasbeen) noticed no wires connected to the petrol gauge, Three connections, Gets even more intriguing. no wires connected yet the Gauge shows full when ignition on, Further investigations during the week, Will update as and when.
Regards
Gareth

G.P.Albrighton

[g4zur]

Hi
Could someone please let me know the layout with regards to wiring to the petrol gauge tank sender unit. Do the wires run underneath the car or enter the cab and run beneath the carpets, going to check the wiring before I swap the gauge.
Many thanks.
Regards
Gareth.

G.P.Albrighton

[saabfast]

Can't really remember from the last time I had the instrument panel apart but I don't think there are separate cables to the gauge, it is fed via the printed circuit.
The wiring generally all runs inside the car, having said that I can't remember where it exits to the sender. Age is a terrible thing....

Alan
Saab 9000 Stg 1
Saab 9000 2.3 FPT Auto (now gone that others might live)
Saab 9000 2.3 LPT Auto
'81 TR7 DHC

[TR Tony]

I think you will find that the wires from the sender come into the car at the rear of the transmission tunnel, and join the loom further up. The wires do not connect directly to the gauge, everything goes through the two flat multipin plugs that connect to the printed circuit at the back of the instrument pod.

At the sender your connections should be Green/black wire to terminal T; Green/orange wire to terminal W, Black wire to earth terminal. Green/black is the wire for the gauge - power goes from the pod to the sender, when the float arm is at it's high point the potentiometer gives full current to ground, as the level drops the resistance changes & alters the gauge reading. If you have a short to earth in the green/black wire the gauge will show full all the time.

Tony

<font size="1">1981 TR7 FHC Cavalry Blue
1980 TR7V8 DHC Jaguar Regency Red - sadly sold!
1977 TR8 FHC EFI Factory development car Inca Yellow</font id="size1">

[g4zur]

Many thanks to Saabfast and TR Tony. I understand now, will further investigate when time allows and advise here on progress.
Regards Gareth.

G.P.Albrighton