Fuel Tank Sender Unit

[4129R]

Can anyone confirm that a Smiths TBS 1514-003 fuel tank sender unit for a Triumph Herald/Vitesse will fit a TC tank? It also has the reference 215846, and is available from Rimmer Bros.

Is it the right length? An MGB AHU 1027 is the right sender, but the arm is too short, and rather than attach a longer arm from the original, I thought the TBS 1514-003 looked the same as the original.

[Dilkris]

Can't help with the question but my original sender (TCS) is out and readily accessible if you need dimensions or a any photo's. 

[4129R]

Can't help with the question but my original sender (TCS) is out and readily accessible if you need dimensions or a any photo's.

Thanks, but I have 2 rusted ones as patterns.

I have ordered the Herald one on eBay. I will report if it is the same length and fitting.

They must have got it from some normal car. They did with nearly all the other parts.

[4129R]

I have just measured the travel of the fuel tank sender unit.

Its full travel in 12", whereas the tank is 21" tall.

So for 9" of fuel level change, the sender unit will not register any movement.

That means it is only actually measuring 57% of the fuel movement, and for 43% of the time, it is not moving at all.

No wonder it stays full for a while, then empties quickly, then still has quite a lot of fuel left as the sender is not recording any movement.

I suppose that is what happens when you use a tall tank and a sender that describes only a small arc.

[Dilkris]

Does this mean that when the fuel tank gauge reads "E" - you still have (for a TCS) 9"of fuel in each tank?   

[4129R]

Does this mean that when the fuel tank gauge reads "E" - you still have (for a TCS) 9"of fuel in each tank?

I have not measured where the float is at its lowest point. I will do that when I fit the new sender, after I either run the fuel level low, or drain the left tank.

[4129R]

I managed to take some measurements.

The sender is central to the tank, so 10.5" above the bottom.

The float bottoms out 7.5" below its centre, so when it is reading empty, there is still 3" of fuel in the tanks = 1/7th full.

If the full travel of the float is 12", the float will be 15" above the bottom, so it will still read full when you have used 6" of fuel = 2/7th.

Since the US/UK cannot agree about the size of a gallon, (or even the spelling of litre), the fuel tank capacity is supposed to be 57 litres.

So when it first reads empty, you will have 1/7th of 57 litres = say 8 litres left.

It will still read full even after you have used around 16 litres.

So I believe the gauge measures from 8 litres to 41 litres in its full travel so it measures only 33 litres from empty to full, so 1/4 full would be 8 + 8.25 = 16.25 litres, half full would be 8 + 8.25 + 8.25 = 24.5 litres, and 3/4 full would be 88 + 8.25 + 8.25 + 8.25 = 32.75 litres. 

E = 8 litres or less.
1/4 = 16.25 litres
1/2 = 24.5 litres
3/4 = 32.75 litres
F    =  41 litres or more.

(If the scaling of the gauge is accurate !!!)

[Dilkris]

I admire your tenacity and thoroughness - the data is good to know - I for one will file it away for future reference.