PDA

View Full Version : TR2/3/3A TR3A gas gauge stuck in "Full"



TR3AD
08-16-2007, 01:35 PM
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
08-16-2007, 01:42 PM
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
08-16-2007, 01:52 PM
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
08-16-2007, 02:03 PM
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
08-16-2007, 02:46 PM
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
08-16-2007, 02:57 PM
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
08-16-2007, 03:29 PM
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
08-16-2007, 03:50 PM
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
08-16-2007, 06:28 PM
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.

TR3AD
08-16-2007, 07:04 PM
All sage advice. I'll try everything and let you know. Thank you!

TR3AD
08-22-2007, 07:59 PM
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
08-22-2007, 08:11 PM
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
08-22-2007, 11:22 PM
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
08-22-2007, 11:28 PM
[quote=TR3AD]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
08-23-2007, 04:56 AM
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
08-23-2007, 05:49 AM
On a TR3, the only gauge you have to switch the wires on when changing polarity is the ammeter.

dklawson
08-23-2007, 07:16 AM
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
08-23-2007, 07:35 AM
[quote=TR3driver 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.[/quote]

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
08-23-2007, 09:50 AM
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
08-23-2007, 09:53 AM
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

TR3AD
08-24-2007, 05:09 PM
No, the car is still positive ground and no wiring changes have taken place since I've owned the car.

TR3AD
08-26-2007, 10:28 PM
Mystery solved. The guage finally did come down after burning through more fuel in the tank. However, the gauge did not move from "full" for almost the first 70 miles of a full tank. By 100 miles the guage read halfway. 160 miles, guage read 1/4 tank. Near empty at 180 miles, then I filled it with 11 gallons. So, the guage seems to now be working properly and I am getting around 16 mpg/city. Thanks for all the advice/suggestions.

Bill
08-27-2007, 07:21 AM
<div class="ubbcode-block"><div class="ubbcode-header">Quote:] However, the gauge did not move from "full" for almost the first 70 miles of a full tank. By 100 miles the guage read halfway.[/QUOTE]
Mine does exactly the same thing.I get around 200 miles to a tank, about 19-20mpg around town, and about 24 on the highway.
I read something a while back about Triumph doing mpg tests and only got a little over 30 with wheel fairings a single Brookland screen and a hard tonneau cover.
I keep mine well tuned but do run heavy oil (20-60 Redline) due to the heat here, so I'm happy with 20.
I guess you could pump the tires up to 50psi, take the wind screen off, put flat hubcaps on steel wheels and run 5w30 oil. All of this might get you an extra 1-2 mpg around town or 3-4 on the highway.

bmurphy7369
09-03-2007, 10:47 AM
I guess I learned something I should have known.. All of these years I was under the impression that all TR3's were NEG ground cars, my first was I am sure. Was it a conversion? I thought the MGA was the only POS ground vehicle I have had! Or do I have it reversed?
On the fuel tank reading, I recall having to bend the sending unit to adjust the guage reading by hand, and I also believe this was the recommended procedure from the factory. As you can see, don't trust anything I say from memory on the TR3's however!

Twosheds
09-03-2007, 10:53 AM
I guess I learned something I should have known.. All of these years I was under the impression that all TR3's were NEG ground cars, my first was I am sure. Was it a conversion? I thought the MGA was the only POS ground vehicle I have had!

Even though this is a Triumph Forum, it's not nice to call an MGA a POS.

Anyway, TR3s are positive ground. Unless they have been converted.

TR3driver
09-03-2007, 11:07 AM
All of these years I was under the impression that all TR3's were NEG ground cars, my first was I am sure. Was it a conversion? I thought the MGA was the only POS ground vehicle I have had! Or do I have it reversed?Both TR3 and MGA were originally positive ground. However, it's very common (and easy) to convert them to negative ground, with several advantages and only non-originality as a disadvantage.

Friend of mine with an MGA learned the hard way about the advantages. He installed a -gnd CB radio (obviously this was some time ago) by insulating the unit and connecting the wires with the right polarity. Worked fine at first, but somewhere between Indianapolis and Cocoa Beach, his rusty rear bumper finally made electrical contact with the rest of the car. Seems he didn't realize that the antenna clamped to the rear bumper was grounded through the set ! The resulting electrical fire almost caused a serious accident; and we finished the trip with jumper leads for the ignition and headlights. The wiring harness was a total loss.

For the TR's, the factory change to negative ground came between TR4 and TR4A. Which is kind of odd, since they didn't start fitting an alternator until the TR5/250.

Randall

bmurphy7369
09-03-2007, 11:04 PM
Mine were both converted then, the two 1959's that is. I haven't even got a wiring harness on the 1957 yet, or picked it up after a year of storage with the seller (may not even have the car at all now come to think of it....)
I know that the '57 MGA was POS earth, and when I bought the car it had already been converted to one 12-volt battery. I really was sure that all TR3's were NEG originally.. thanks for the lesson and clarification. /bcforum/images/%%GRAEMLIN_URL%%/thirsty.gif

PS - I really need to get the flatbed out and haul the TR3 home... It is basically a rolling tub restoration project, but I decided I wanted to start ground-up and body-off on this one. By the way, I only mentioned the "A" for the sake of comparison, I always preferred the TR's, although the A's had beautiful lines. The TR's are by far the better driver's car, the power from the old Ferguson block and the dependability and simplicity of the build is impeccable!