FZRSupport: the FZROnline Archive

I burned threw the fuel sensor again. What am I doing wrong?


I hooked it up like the beautiful drawing above with a 10 amp fuse in between. The first time after switching the power on, the fuel sensor (out of the tank) starts to smoke and the light comes on, light on is good, smoking not so much. But then after I switch the power off and on again the light never comes on anymore, probably because it burned. I connect the + wire to a switched line and the light is in between ground and the sensor.

This is the sensor:

What am I doing wrong that the sensor just starts smoking and doesn't work after anymore?

from what i've discovered, the sender uses the fuel as a coolant.. therefore if it's not submerged in fuel, or something of equal viscosity/gravity, then it'll get too hot?

Pr1ngle wrote:from what i've discovered, the sender uses the fuel as a coolant.. therefore if it's not submerged in fuel, or something of equal viscosity/gravity, then it'll get too hot?

Yes...but it is designed to work like that.
When no fuel to cool then reserve is emulated....
As it heats ...the bi metal/diode switch inside makes/breaks the circuit...

I have put up pics of one cut open (courtesy of Chris Reed/Creed) loads of times.


Its quite a complicated set up...there is a resistor fitted on the 1000 model that acts as a heat sink...
Also if you want to fit a warning light you need a 5V LED ...nowt else works.
Too tired to explain properly now but google "5 volt LED mod "and you should find the info that describes the circuit.

So does it basically mean that the sensor is working on 5v and not 12v?

@willandrip

fuel system appears to be something that is popping up frequently, how about creating a master post with everything you know so that us newbies have a place to read up?

Pr1ngle wrote:@willandrip

fuel system appears to be something that is popping up frequently, how about creating a master post with everything you know so that us newbies have a place to read up?

Well...much as I would like to.....time or lack of it really prevents this scenario.

I no longer actively research or post on m/cycle forums to the extent I previously did.
In fact I rarely have time to even enter my own garage where 16 m/cycles are languishing in varies states of abandonment.

I only post on here through "habit" with what info I can recite from memory> search the web...the info is out there and easily sourced.
Join here..."Stig's" site (he is a member on this forum too) and someone will point you to all the info on the subject.
http://www.exup1000.co.uk/

N.B. The fuel level sensor system is virtually identical in operation on all models fitted with that circuit.. some components do differ but only in fitment not circuitry/operation.

I know that feeling all too well mate, apart from the 16 motorbikes... I've only ever had 5 on fleet at one time haha!
...infact come to think of it, i'm on four at the moment when the other half's Cagiva 500 returns from the engine transplant shop

...was just a thought, i'm sure I wouldnt be the only one eternally grateful for it

Grateful don't pay the bills...Lol.

lecoen wrote:I burned threw the fuel sensor again. What am I doing wrong?


I hooked it up like the beautiful drawing above with a 10 amp fuse in between. The first time after switching the power on, the fuel sensor (out of the tank) starts to smoke and the light comes on, light on is good, smoking not so much. But then after I switch the power off and on again the light never comes on anymore, probably because it burned. I connect the + wire to a switched line and the light is in between ground and the sensor.

This is the sensor:

What am I doing wrong that the sensor just starts smoking and doesn't work after anymore?

You have it wired backwards, use the Brown signal wire as the warning lamps positive, connect the warning lights negative to the fuel senders Green/White wire, tap the fuel sender units Black wire into the fuel pumps Black wire.

Job done.

viewtopic.php?f=64&t=6536&start=15

Read that I think it also describes how to use a LED as a low fuel warning lamp.

It says TK posted the solution. It was me, some glitch I suppose. If you need further assistance feel free to contact me

Pr1ngle wrote:from what i've discovered, the sender uses the fuel as a coolant.. therefore if it's not submerged in fuel, or something of equal viscosity/gravity, then it'll get too hot?

Bullshit. I'll explain why. So your riding happily along you run low on fuel, you then run out of fuel but your tank is still full of explosive gasses. ......

The OP has his set up wired up back to front, killing/frying the diodes in the fuel sender unit. Wire a diode incorrectly, it will get hot and burn out.

mawler666 wrote:Wire a diode incorrectly, it will get hot and burn out.

Only if the reverse voltage rating is exceeded. LEDs have some pretty fluffy ratings, but why would they use a diode that would be vulnerable in this application? If it's just guarding a bimetallic strip, use a frickin' 1N4007 and be done with it!

mawler666 wrote:viewtopic.php?f=64&t=6536&start=15

Read that I think it also describes how to use a LED as a low fuel warning lamp.

It says TK posted the solution. It was me, some glitch I suppose. If you need further assistance feel free to contact me

Hi Mawler...would I recall your name from posts way back....looks like you had to re-register...?

Good to see you keeping an eye out anyhow....

You are quite correct in stating that a fuel sensor will not burn out if un- submerged...it's how they operate by temp opening/closing the circuit. They do get warm to the touch , though not exactly toastie hot.

thanks for calling me out on that bro ::thumbsup

...it was a theory... I didn't mean Chernobyl-hot, i meant tepid warm and that there was a resistor (diode) stopping it from getting "too" hot.
I apologise pal, i'm still learning