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TR2/3/3A TR3A gas gauge stuck in "Full"

TR3AD

Freshman Member
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TR3A gas gauge stuck in "Full"

I thought I was getting spectacular gas milelage on my 1960 TR3A, until I realized that the fuel guage is consistently registering full, even when the tank is near empty. (Guage registers empty when ignition is off) Is there an easy way to determine what's wrong without removing the guage, fiddling with wires or messing around with the sending unit? Could the float just be stuck? I'm reluctant to shove a stick into the gas tank for fear of breaking something. Thanks for any suggestions...
 

Tomster

Jedi Knight
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Re: TR3A gas gauge stuck in "Full"

Bend a hook on the end of some wire (Clothes hanger) hook the float rod when looking thru the filler cap (should be real easy to see it) and GENTLY swing it up and down while watching to see if the dash gauge moves. Check for wire continuity next
 

Twosheds

Darth Vader
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Re: TR3A gas gauge stuck in "Full"

My gauge sticks on F when the tank is full, but a knuckle rap on the gauge glass frees it.

NOTE: This post is serious.
 

Tomster

Jedi Knight
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Re: TR3A gas gauge stuck in "Full"

An old friend yelled at me a long time ago "Never be bangin' on dem gauges ya fool! Be bangin' on the mounts themstead!"
I caught the drift "Rap the dash, not the gauge"
 

Adrio

Jedi Knight
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Re: TR3A gas gauge stuck in "Full"

I remember back in the stone age when I as a student, we were told to rap beside the gauges on the aircraft rather then on the glass. I think they must have had some hammer knuckled students with big rings that cracked the glass in the past. To this day I still do the same thing and have never brocken a glass face.
 

Twosheds

Darth Vader
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Re: TR3A gas gauge stuck in "Full"

Adrio said:
I remember back in the stone age when I as a student, we were told to rap beside the gauges on the aircraft rather then on the glass. I think they must have had some hammer knuckled students with big rings that cracked the glass in the past. To this day I still do the same thing and have never brocken a glass face.

I guess I was absent the day the instructor gave that lesson!

Some aircraft have instrument panel shakers that prevent the gauges from sticking.
 

NickMorgan

Jedi Knight
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Re: TR3A gas gauge stuck in "Full"

I don't think that you gauge is "stuck" as it returns to zero when the ignition is switched off. I suspect that you have a wiring fault. I would guess it is the wiring to the back of the gauge, as if it was a bad earth or break in the wiring the gauge would read zero all of the time.
 

TR3driver

Great Pumpkin - R.I.P
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Re: TR3A gas gauge stuck in "Full"

NickMorgan said:
I would guess it is the wiring to the back of the gauge, as if it was a bad earth or break in the wiring the gauge would read zero all of the time.
Well, at least I'm not the only one that got tripped up on that /bcforum/images/%%GRAEMLIN_URL%%/smile.gif

The TR2-3 fuel gauge works backwards to the later gauges, it will read full (or past full) if the wire to the tank sender is open or the sender isn't grounded.

https://mgaguru.com/mgtech/electric/fg_01.htm

Could still be a bad ground to the gauge, or the gauge itself has failed, but I'd check the wire to the tank first. One easy first check might be to temporarily ground the 'T' terminal on the gauge (the one with the green/black wire to the tank) and see if it now reads empty. If so, the gauge is working and the problem is farther down the line. Next ground the terminal on the sender, if that doesn't send the gauge to empty then it must be the wire.
 

Geo Hahn

Yoda
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Re: TR3A gas gauge stuck in "Full"

Tomster said:
Bend a hook on the end of some wire (Clothes hanger)...

Maybe I'm overly cautious but I use a length of 12ga copper wire for this purpose.
 
OP
T

TR3AD

Freshman Member
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Re: TR3A gas gauge stuck in "Full"

Tried pushing down the float inside the take and the guage did indeed go down, but only halfway when pushed to the bottom of the tank. So it seems the guage is reading information, but perhaps incorrectly. Tank now registers a little above half full after 100 miles driven on a full tank, so I am thinking this may be fixed, but I will wait until more fuel is burned before I determine if the gauge is misreading the tank. Question: About how many miles can you expect from a full tank on a TR3A? (Don't want to get stranded with an dry tank and a fibbing fuel gauge!)
 

dklawson

Yoda
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Re: TR3A gas gauge stuck in "Full"

Since you've learned that the system is working, visit the MGA Guru link above and read up on the magnetic gauges. I don't remember if he mentions this or not, but the GAUGE itself also needs a good ground, not just the sending unit. Before attempting to re-calibrate your gauge as described at MGA Guru, make sure that BOTH the sending unit and the gauge have good ground connections. When I'm working with the older gauges I run a separate ground wire from the case (or mounting stud) directly to the car's chassis.
 

TR3driver

Great Pumpkin - R.I.P
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Re: TR3A gas gauge stuck in "Full"

TR3AD said:
Question: About how many miles can you expect from a full tank on a TR3A? (Don't want to get stranded with an dry tank and a fibbing fuel gauge!)
Unfortunately varies considerably. With the stock 83mm liners, overdrive and everything just right, mostly freeway miles at 60-70 mph, you should be getting close to 30 mpg giving 300 miles or more from a 12 gallon tank.

With my modified engine, short tires, etc. and driving about a 50/50 mix of city & freeway, I average about 20 mpg, meaning about 200 miles/tank.
 

DNK

Great Pumpkin
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Re: TR3A gas gauge stuck in "Full"

TR3driver said:
TR3AD said:
Question: About how many miles can you expect from a full tank on a TR3A? (Don't want to get stranded with an dry tank and a fibbing fuel gauge!)

That is a trick question. After the first mile the tank won't be full anymore /bcforum/images/%%GRAEMLIN_URL%%/devilgrin.gif
 

RB

Freshman Member
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Re: TR3A gas gauge stuck in "Full"

Has the car been converted to negative ground?
If so that might be the problem. I'm not sure if you have to switch the wires on the gauge when converting.
 

martx-5

Yoda
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Re: TR3A gas gauge stuck in "Full"

On a TR3, the only gauge you have to switch the wires on when changing polarity is the ammeter.
 

dklawson

Yoda
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Re: TR3A gas gauge stuck in "Full"

The gauge system (pre-stabilizer as here... or post stabilizer on later Triumphs) is not dependent on the polarity of the car. You do not need to change the gauge wiring when you switch the car's polarity.
 

Adrio

Jedi Knight
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Re: TR3A gas gauge stuck in "Full"

TR3driver With the stock 83mm liners said:
Is that 30 miles to the AMERICAN gallon on the highway?? If so I have some tunning and work to do on my TR3 as the best I have got is 24 miles to the CANADIAN gallon
 

TR3driver

Great Pumpkin - R.I.P
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Re: TR3A gas gauge stuck in "Full"

Adrio said:
Is that 30 miles to the AMERICAN gallon on the highway??
Yes, although perhaps not with the gasohol we now have to burn. Never did that well myself (except maybe going down a mountain /bcforum/images/%%GRAEMLIN_URL%%/smile.gif ), but I have a friend that does. He's also a much more conservative driver than I am; doesn't try to set records for 0-60 times /bcforum/images/%%GRAEMLIN_URL%%/jester.gif
 

TR3driver

Great Pumpkin - R.I.P
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Re: TR3A gas gauge stuck in "Full"

martx-5 said:
On a TR3, the only gauge you have to switch the wires on when changing polarity is the ammeter.
/bcforum/images/%%GRAEMLIN_URL%%/iagree.gif
 
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