3TJ Reserve fuel mode not working?

[JonathanCox]

Yo

my 3TJ is nearly done, I'm trying to get the reserve mode working but I can't seem to

The engine should drop one or more cylinders to imitate the effect of running out of fuel. when fuel goes below the sender unit inside the tank as we know

I've just got a resistor off ebay after realising I needed one, that's plugged in

Bought a brand new genuine reserve switch, plugged in.

The wiring loom I remade myself as the one on the bike was hacked about badly. Everything is going to the right places.

I have the sensor outside of the tank to test. The bike doesn't change note at all when the sensor is submarged in fuel or not. and switches on both modes..

I can only think that this system only works when the bike is in motion? and not stood idling? I'm going to put the sensor back in the tank, get it on the road and see if it'll work then

Kinda annoying me now :/ Any thoughts?

[willandrip]

Any part of that system that has failed/does not work or is missing /not plugged in and the bike will act exactly as
you have described.

The system is so designed as to if there is any problem it will run in the default setting which is the same as if the fuel level has gone below the sensor AND the switch has been set to reserve.

The system is exactly the same as the 1000 unit and many have ran out of fuel with this fault.

The movement of the bike has nothing to do with the sensor acting up.
The sensor is very hard to test when not immersed.
There is a very good mod using a 5v LED as a low fuel indicator.

viewtopic.php?f=37&t=38611&hilit=+fuel+sensor

viewtopic.php?f=37&t=39192&hilit=+fuel+sensor

Some of the links from the above are now dead unfortunately.

[JonathanCox]

Thanks for the reply. after playing around I've managed to get it working. However it works differently to what I thought.

I felt the fuel pump when normally running, and the pump pulsates every few seconds, with the sensor taken out of the tank the diode got a little warm, not hot

with the sensor immersed in my external fuel tank hanging from the bike, the fuel pump was still pulsating once every 4 seconds or so.

When I removed the sensor, after a minute or so, the fuel pump stopped pulsing. So I can imagine after a short distance actually riding the bike would choke a little

I then put the sensor back in, it made the sound of something hot going into cold liquid, so it was operating, the fuel pump then pulsated as normal.

Flicking the switch to reserve made the fuel pump pulse no matter what, which would of ran the tank dry
So in all, perhaps I expected it to cough and change engine note straight away, but it takes time.

I wanted to post this in case anyone comes across this post in the future, I'm always finding old 400greybike posts from 2008 and they've solved what I was looking for

[willandrip]

As stated in previous posts;
The thermal sensor takes time to heat and indicate that the low fuel level is reached by switching off the fuel pump and further time for the carb bowls to be emptied.

The resistor is included to prevent the sensor from overheating when exposed; the system runs (in the default setting)with it broken or bypassed/missing but the sensor will overheat and eventually fail.

[JonathanCox]

Yep, I thought that the ignitor would cut a cylinder or two streaight away, so I'm glad thats cleared up

I did buy a new tank sensor and swapped the stalk over so its at the correct height, however this was before I got the resistor, so i must of burned it out. I soldered my old thermal diode in and its working

happpy dayssss