41 replies to this topic

[stevelane]

I have never had a working fuel guage, I know the guage work as I've joined the wires together and I know the sender works as I've tried more than one that worked elsewhere but have never had an accurate reading

I was advised to replace a voltage stabiliser behind the fuel guage but I've just taken it apart and there isn't even one there.

Have I bought the wrong part for the wrong guage? If not, where am I putting it?

If so, what else could be wrong?

[Austin mini 30]

what year of car is it? My 89 austin mini doesnt have a stabilizer and fuel gauge only reads over half way, doesnt register under that.  try shorting the sender wires together and see if the gauge goes to the very top. 

[stevelane]

It's 92 but it's been restored before so the gauges might not be what was 1st in there.

My guage only ever goes two thirds of the way up and then drops to nothing over only a few miles so I never know what I've got left

[stevelane]

Have shorted the wires before so I know the guage itself works

[Dan]

Minis from '88 on had the stabiliser integrated into the instruments rather than as a separate component. There is a thread in the FAQ section that will help you look into it.

[Austin mini 30]

Thats good then, rules out the gauge really. What can happen is the float in the tank can actually fill up with petrol, weigh it down making it read less than it actually is. not sure what else it could be apart fron the seander, but you know thats ok.

[stevelane]

Minis from '88 on had the stabiliser integrated into the instruments rather than as a separate component. There is a thread in the FAQ section that will help you look into it.

Oh excellent, thanks Dan, will give it a look

[stevelane]

Minis from '88 on had the stabiliser integrated into the instruments rather than as a separate component. There is a thread in the FAQ section that will help you look into it.

.

Just found it, brilliant thread, just what I need, couldn't see it before

[dklawson]

Keep in mind that where an electric temperature gauge is fitted, it is also powered by the voltage stabilizer.  If both the temperature and fuel gauges are reading incorrectly that suggests a voltage stabilizer problem.  If the temperature gauge reads correctly while the fuel gauge does not, that says the problem is not with the stabilizer but something in the fuel gauge circuit itself.

[stevelane]

Keep in mind that where an electric temperature gauge is fitted, it is also powered by the voltage stabilizer.  If both the temperature and fuel gauges are reading incorrectly that suggests a voltage stabilizer problem.  If the temperature gauge reads correctly while the fuel gauge does not, that says the problem is not with the stabilizer but something in the fuel gauge circuit itself.

Ok, but when I short the two wires it shoots to the top, as far as I know the temp guage is ok, so what other options do I have?

[dklawson]

If the gauge goes beyond full with the sender wires shorted that says that the gauge itself is functional.  Since the temperature gauge appears to be working properly, that says the voltage stabilizer is working properly.

 

In previous posts you said you have tried different sending units.  How long did you leave them in the tank and what year car did they come from.  According to Mini Spares, later cars (from '92) used a sending unit with a special bend in the float arm.  I have been told that if the wrong sender is fitted to those later tanks the float will not move up and down properly.  There is also the possibility that your sending unit float has a leak and is partially full of fuel as Austin Mini 30 said above.

[stevelane]

If the gauge goes beyond full with the sender wires shorted that says that the gauge itself is functional.  Since the temperature gauge appears to be working properly, that says the voltage stabilizer is working properly.
 
In previous posts you said you have tried different sending units.  How long did you leave them in the tank and what year car did they come from.  According to Mini Spares, later cars (from '92) used a sending unit with a special bend in the float arm.  I have been told that if the wrong sender is fitted to those later tanks the float will not move up and down properly.  There is also the possibility that your sending unit float has a leak and is partially full of fuel as Austin Mini 30 said above.

The others I used never went in the tank, I just hooked them up to the wires and moved them outside to simulate the tank filling and got exactly the same reading as I get all the time

[dklawson]

If I understand your post, you attached donor sending units to the sending unit wires and manually operated their float arms through their range of motion with the ignition on and you did NOT get full travel of the fuel gauge from empty to full.  However, the temperature gauge is working correctly.  Is that an accurate summary?

 

If that is correct, perform a test on the temperature gauge just to make sure it really is OK.  Borrow or buy an infrared thermometer and drive the car for a while to get the engine up to operating temperature.  Open the bonnet and take temperature readings on the thermostat housing, top hose, and the header tank at the top of the radiator.  Compare the highest reading you get with the thermostat rating and what the car's temp gauge is showing.  On Smiths gauges, the needle pointing straight down into the "N" range is typically about between 180 and 190 oF (85 oC).  I don't know for a fact but I assume the later Nippon Seiki gauges would be calibrated about the same... others will have to confirm this. 

 

If there is a significant mismatch between the temperature shown on the gauge and that measured on the t-stat housing, hose and radiator and the temperature gauge is reading significantly low, that says the voltage stabilizer is at fault (for both gauges).

 

If your temperature gauge shows a temperature close to what you measured with the infrared thermometer that confirms that the voltage stabilizer really is working correctly and the problem with the fuel gauge is likely to be the fuel gauge or the gauge wiring.  Since you said the gauge is reading low, it could be excess resistance from some very, very dirty connections either at the gauge, the sending unit, or the earth connection (far end) of the black wire at the sending unit.

[stevelane]

If I understand your post, you attached donor sending units to the sending unit wires and manually operated their float arms through their range of motion with the ignition on and you did NOT get full travel of the fuel gauge from empty to full.  However, the temperature gauge is working correctly.  Is that an accurate summary?
 
If that is correct, perform a test on the temperature gauge just to make sure it really is OK.  Borrow or buy an infrared thermometer and drive the car for a while to get the engine up to operating temperature.  Open the bonnet and take temperature readings on the thermostat housing, top hose, and the header tank at the top of the radiator.  Compare the highest reading you get with the thermostat rating and what the car's temp gauge is showing.  On Smiths gauges, the needle pointing straight down into the "N" range is typically about between 180 and 190 oF (85 oC).  I don't know for a fact but I assume the later Nippon Seiki gauges would be calibrated about the same... others will have to confirm this. 
 
If there is a significant mismatch between the temperature shown on the gauge and that measured on the t-stat housing, hose and radiator and the temperature gauge is reading significantly low, that says the voltage stabilizer is at fault (for both gauges).
 
If your temperature gauge shows a temperature close to what you measured with the infrared thermometer that confirms that the voltage stabilizer really is working correctly and the problem with the fuel gauge is likely to be the fuel gauge or the gauge wiring.  Since you said the gauge is reading low, it could be excess resistance from some very, very dirty connections either at the gauge, the sending unit, or the earth connection (far end) of the black wire at the sending unit.

Thank you for all your help on this, makes a lot of sense

The gauge will go up to three quarters full and then drop to almost nothing and then stay there for ages

I have hot the parts from maplins to do what you suggest in the other thread so I'm tempted to try it anyway, that way I will find out if the temp gauge is as accurate as I think it is

I presume I wouldn't be doing any damage that I can then reverse by doing that?

If it works then great, if not, nothing lost and I can start investigating the other areas

[dklawson]

Well there are some other less intrusive things you could try before making the external voltage stabilizer conversion.  

 

First, try a mechanical inspection.  Shine a flashlight in the tank to see if the float is floating.  If it is not, you know there is a mechanical issue to sort out (binding arm, perforated float, etc).  

 

If the float appears to be floating, add some resistors to your Maplin order.  Buy a small quantity of 5%, 1/2 Watt resistors rated at 33 Ohms, 130 Ohms, and 240 Ohms (or close to these values).  These will be used to simulate the sending unit.  Disconnect the two wires at the sending unit.  With the ignition switch in the run position, insert the 240 Ohm resistor in the two wire terminals making sure the resistor leads are making good contact with the terminals.  The gauge should read close to empty but the needle should be up off its bottom position.  Replace the 240 Ohm resistor with a 130 Watt resistor.  After a few moments the fuel gauge should go somewhere near 1/2.  Finally try the 33 Ohm resistor.  The tank should read close to full but not be pegged all the way to the top.  If you don't get the empty-1/2-full results with these tests, repeat the tests by inserting the resistors in the green/black sending unit wire terminal and connecting the other resistor lead to a wire that you run directly to the battery (-) terminal.  If you get the correct empty-1/2-full results connected directly to the battery terminal, the black sending unit wire has an earth problem.  If neither test method makes the fuel gauge read correctly then you have cause to try the external voltage stabilizer conversion.