Fuel level sensor

[Mang]

Can anyone tell me if the tank is empty should the sensor wiring be open or closed. If closed then if you run the bike with the tank off (tank on shelf and long fuel line) do you need to put a jumper across the reserve sensor wiring on the harness. My sensor is not working so I need to be sure.

[willandrip]

When fuel level is below sensor then circuit closes causing TCI to cut supply to ignition imitating running out of fuel.
Putting electric switch to res position then overides this circuit imitating turning on reserve tap.
The sender is a diode thermal switch-fuel keeps it cool.
When either the switch or sender fails reserve is selected by default.
You cannot test sensor unit accurately on bench with meter.
You do not need to do anything except ensure fuel supply if using a remote tank..
If any further reading on sensor is required go to www, fzr 1000 forum=there is loads on there about it. (same system and components). Especially look for the 5Volt LED mod.
Have you removed sensor and inspected feed wire for break (goes brittle over time being immersed in fuel) and can be re soldered.? Switches play up also but can be usually fixed by WD40 spray and vigorous off/on positions to clean copper contact corrosion.Sensors are not refurbishable=they are tiny diode inside the canister. R series are the same sensor but on a different stalk,no reason not to unsolder and resolder to fzr stalk but the FZR 1000 one is a direct fit (usually £10 used) might be a different level though!!!

[Mang]

Thanks for your help Willandrip.

So to get this right the tank is off and the wiring is disconnected. I assume that only when the fuel level drops to reserve does the sensor issue any signal, so having the tank off and disconnected does not stimulate the TCI to think its on reserve. sooty to be so pedantic.

Mang

[willandrip]

If the switch breaks,the wiring is disconnected or the sender fails or is disconnected the TCI and pump runs the tank dry. This is the default setting and is why many run out of fuel;their system develops a fault they do not know about,the bike stutters.they switch to reserve but fuel has already been used up=tank is bone dry.
The sensor runs 12 volts when submerged -when it is exposed it reduces voltage to 7volts=this sends altered signal to tci which makes pump stutter,this is why a 5volt LED must be used for an indicator if desired (5+7=12)
12 v LEDs wont work.
You could pipe pump up to a petrol tanker without any wiring and it would run perfectly till every bearing in the engine failed ie forever nearly. The sensor or wiring does NOT need to be fitted for bike to run correctly. Only when all parts and wiring is intact does the "reserve" system come into operation.
I presume you are trying to diagnose a misfire problem and suspect it is the reserve system that is causing it !.
Am I correct?
Have you inspected sensor wiring by removing it .? It usually breaks where soldered to base plate. If not broken wire then thermo diode is u/s.Also on the pump is a ceramic resistor that stops system overheat if running continiously with reserve system fault or for people who leave switch on reserve permanantly (1000r,s definate but as I have not access to 400 with electric reserve can only speculate).
You would be very worried how hot that sensor gets when working correctly and not submerged but being sloshed by fuel and fumes! IIRC its about 80 celcius.