• The Roadster Factory Recovery Fund - Friends, as you may have heard, The Roadster Factory, a respected British Car Parts business in PA, suffered a total loss in a fire on Christmas Day. Read about it, discuss or ask questions >> HERE. The Triumph Register of America is sponsoring a fund raiser to help TRF get back on their feet. If you can help, vist >> their GoFundMe page.
  • Hey there Guest!
    If you enjoy BCF and find our forum a useful resource, if you appreciate not having ads pop up all over the place and you want to ensure we can stay online - Please consider supporting with an "optional" low-cost annual subscription.
    **Upgrade Now**
    (PS: Subscribers don't see this UGLY banner)
Tips
Tips

How to test and adjust a fuel gauge

bugimike

Yoda
Offline
That is awsome Jack! the definitive word, I would say! Did you test and set yours? How does it work?
 
OP
jlaird

jlaird

Great Pumpkin
Country flag
Offline
Not yet. Been working on a few other things to get it driveable.
 

PeterC

Jedi Warrior
Offline
Careful, there are at least 2 styles of fuel gauges on Spridgets. I know the early wont work with the later sender, and vice versa. I'm not certain whether Barney's MGA is the same type as Bugeye or as later Spridgets.

If pressed I could get more details.
 

DrEntropy

Great Pumpkin
Platinum
Country flag
Offline
Peter, that gauge is the early unstabilised one. Induction coils and a gimballed movement. The stabilised one is a bi-metal affair.
 
OP
jlaird

jlaird

Great Pumpkin
Country flag
Offline
Beleive me, that is a Bugeye gauge. Mine has all those parts, hehe.

Now if I can just get it figured out. Think I will need some resistors, Radio Shack??
 

Morris

Yoda
Offline
Cool article.

You should be able to get those resistors at Radio Shack no prob.
 
OP
jlaird

jlaird

Great Pumpkin
Country flag
Offline
Next time I am up town I will do so. I am just persistant enough to fight it through.

Look how the case also needs to be grounded for the gauge to work properly, intresting.
 

regularman

Yoda
Country flag
Offline
I have the later model, but I calibrated mine the old fashioned way. filled the tank adjusted for full. took half out of the tank, adjusted. took all out but about 1/2 gallon adjusted for empty. I kept pouring gas in and taking it out and playing with the zero and span until I got it where I thought it ought to be.
 

PeterC

Jedi Warrior
Offline
DrEntropy said:
Peter, that gauge is the early unstabilised one. Induction coils and a gimballed movement. The stabilised one is a bi-metal affair.

OK... then tell me about the "stabilized" one I have in my Mini..... never reads anything. How to test?

Peter
 
OP
jlaird

jlaird

Great Pumpkin
Country flag
Offline
Man Peter, you ask some hard questions. I just found this with help this morning and now you want to know about stabilized ones. Tis my understanding the stabilizer supplys 10 volts rather than 12, shrug. Suspect it might be about the same.
 

regularman

Yoda
Country flag
Offline
If its a mini just give it a roll. I was in two mini rollovers in the UK. The last one was in a round a bout that had black ice in it. Three of us in it and it rolled over. We rolled it back and the top was a mess but the gas gauge worked and it had never worked until then. Week later that one was at the bone yard cause the windshield was coming out /bcforum/images/%%GRAEMLIN_URL%%/lol.gif
 

Sarastro

Obi Wan
Silver
Country flag
Offline
For what it's worth, below is a copy of my project notebook comparing the resistances I measured from the Bugeye fuel gauge to the MGA. I don't remember how I determined that the sender resistance was 0 to 90 ohms; probably measured 90 ohms when the tank was full and assumed it would be zero, like the MGA, when empty. So, take it with a grain of salt.

If you use resistors to cal the gauge, remember a couple things. First, you should get 1-watt resistors, because that's about how much power will be dissipated in them. Half watt (and smaller) are easier to find, but might get stunningly hot or even burn out. Second, resistors are available only in standard values. Some 'standard' values are not commonly encountered, though. So, assuming that the sender is linear (a BIG assumption), you want the closest standard values to 22.5, 45, and 67.5 ohms. These are 22, 47, and 68 ohms, and should be available at Radio Shack. Again, check the resistance of your sending unit to be sure I'm right on the 0-90 number.

I do wonder why LBCs all seem to use this funny arrangement of three coils instead of a simple, one-coil meter movement for the fuel gauge. I suspect it is some clever way to make it less sensitive to the system voltage, which, as we know, varies a lot. But it can't be perfect, since later cars have that profoundly bizarre bimetallic voltage stabilizer, which, I suspect, works about as well as high-heeled sneakers.
 

dklawson

Yoda
Offline
The early non-stabilized gauges are easy to identify as the DR mentioned above. They are "fast acting" when any resistance changes happen, the bimetallic ones respond SLOWLY. I'm sure there were different ranges used on the non-stabilized gauges, but every one I've seen was set up to work with senders that operated from 0 Ohms empty to 90 Ohms full. This is also the range used with a lot of GM sending units from the 1960s.

The stabilized gauges operate at 10V as mentioned above and the fuel sending unit operates in the opposite direction with a wider range. The typical, nominal range is 240 Ohms empty to 33 Ohms full.

Peter, to test your gauge and it's sender is fairly simple. Rather than repeat all the steps here, download my PDF on the stabilizer. It has troubleshooting steps in it.
https://home.mindspring.com/~purlawson/files/SmithsVoltageStabilizer.pdf

If your gauge is the non-stabilized type (on Minis your car would be built before September 1964), you'll find additional information relative to that system on the MGA Guru link at the start of this thread. PM me if you need additional help.

EDIT:
Sarastro, the non-stabilized systems weren't unique to the LBC world. They were on a lot of US cars prior to the 1960s. As you suggest, the bridge arrangement was fairly immune to variations in the car's operating voltage. They do bounce around a lot though and calibrating them is a little touchy.
 
OP
jlaird

jlaird

Great Pumpkin
Country flag
Offline
Boy is that a nice write up.
 

PeterC

Jedi Warrior
Offline
Beautiful, Doug.... I think your test is .. shall we say, less "intrusive", than Kim's!

We're supposed to get above freezing this weekend, so I might revisit the gauge. The stick and spare gallon routine gets old. I do have a stabilizer, and have looked and tested stuff back there, but there is evidence of some smoke having leaked at some point in the past.

Thanks again. Peter
 
OP
jlaird

jlaird

Great Pumpkin
Country flag
Offline
That durn smoke again. We gona need a fix for that.
 

DrEntropy

Great Pumpkin
Platinum
Country flag
Offline
Just got back here and caught up. Thanks again Doug, for your article. And again: It's the best written gauge document I've seen. Anyone fussing with Smiths instruments needs to have it on-hand. Ya oughta get "royalties"! /bcforum/images/%%GRAEMLIN_URL%%/cheers.gif
 

dklawson

Yoda
Offline
Thanks all. If you didn't notice... I like gauges. I think the best document out there is the one written by Anthony Rhodes on the Jaeger and Smiths speedometers. For the early gauges and electrics, the MGA Guru site is the best I've seen.
 

drooartz

Moderator
Staff member
Gold
Country flag
Offline
I've got this thread bookmarked. Lots of good info here, and I've got all sorts of gauge work to do this year (Tunebug's only working gauge is the oil/water gauge). It's not too expensive, and I can do it inside the warm house!

Of course, like always, I've got very little idea what I'm doing, but at least y'all do and I can sponge up the knowledge. /bcforum/images/%%GRAEMLIN_URL%%/grin.gif
 
Similar threads
Thread starter Title Forum Replies Date
petnatcar Compression Test Record Form Austin Healey 0
kodpkd Compression Test Results Austin Healey 1
M Overdrive Pressure Test Austin Healey 2
RJS General TR Oil Pressure Gauge - Test Triumph 11
JohnGone MGB Help getting my 1980 MGB to pass CA smog test MG 19
PAUL161 T-Series 5 Speed Road Test MG 25
Rob Glasgow First Test Austin Healey 6
K TR2/3/3A Test Triumph 0
glemon Test FORUM Navigation Questions 4
AUSMHLY HD8 drop test time in seconds Austin Healey 3
AUSMHLY Compression test results Austin Healey 17
HealeyPassion EFI AH Initial Test Day... Austin Healey 6
Michael Oritt Every ride is a test ride Austin Healey 9
roscoe Leakdown test [long read] Austin Healey 11
Y Passing the smog test MG 17
KVH General TR Overdrive Pressure Test Triumph 17
Jeepster BJ8 Servo/ brake booster test Austin Healey 1
D Test image post FORUM Navigation Questions 1
D Lilly test runs Austin Healey 4
F TR2/3/3A Compression Test Triumph 13
M Carb emission test Austin Healey 5
RJS General TR Head Gasket Test Fit Triumph 5
Tinkerman TR2/3/3A SU H6 Rebuild Bench Test Triumph 3
KVH General Tech Leak Down Test Triumph 17
T TR2/3/3A How do I test overdrive relay diode jumper? Triumph 2
T TR2/3/3A SU Piston Drop Test Triumph 4
Steve1970 TR6 Carb air piston test, still results in stall even when adjusted rich Triumph 11
toysrrus TR2/3/3A How to test fuel gauge & sending unit? Triumph 10
T TR2/3/3A 4th Test drive Triumph 12
S TR4/4A How to test Overdrive out of the car Triumph 45
P TR6 Latest compression test Triumph 11
RickB 1980 MGB on test drive suddenly loses electrics and dies - what to look at? Spridgets 46
gbtr6 TR6 Test starter system with engine out? Triumph 16
NutmegCT Memory test Other Cars 9
J TR6 Test 75 TR6 Hazard Switch? Triumph 12
S TR2/3/3A Test an overdrive trans. Triumph 6
T TR6 TR6 compression test Triumph 12
D LSR test run Racing 2
T Wedge Riddle me this guys | TR8 SMOG test issue Triumph 13
C High test or regular gas? Jaguar 4
C How to test shocks? Austin Healey 7
M Compression test results Austin Healey 11
NutmegCT TR2/3/3A Sports Cars Illustrated TR3 road test Triumph 17
J MGB Smog test fail MG 11
B Smiths RVI Positive Ground Tachometer Bench Test ? Austin Healey 24
Lukens TR2/3/3A Is there a subforum that I can send "test" posts? Triumph 3
NutmegCT General Tech Condenser test? Triumph 38
B test a wiper motor? Spridgets 13
R TR6 How does one test the voltage regulator in th late TR6? Triumph 2
G TR4/4A tr4a vacuum test Triumph 13

Similar threads

Top