Fuel Gauge and Temperature Gauge

[dross1]

Hey guys! When I bought my Ducati the fuel and temperature gauges weren't in working condition. Today was spent taking the bike apart, studying it, cleaning carb and jets, then putting it back together. Upon putting it together, I noticed this (what I believe to be the fuel sensor that tells when tank is empty) was disconnected. I connected it and there was no difference in the fuel gauge. However... the gas light came on telling me I was near empty or empty (even though I just filled the tank... silly me )
Then the light shut off, fuel gauge went to full, then sank back to empty. Could I have shorted something out by plugging in what needed to be plugged in? Granted I go by the miles per tank, I would like to get the fuel gauge working.

As for the temperature gauge... I had no luck with that. I noticed a disconnected wire, but traced it to nothing so I left it alone. Has anyone encountered these problems before or does anyone know how to fix this?

Note: I am not great with electrical work, though I haven't had a problem with any electrical work I have done... yet.

Thanks all,

Dustin

[jcslocum]

Dustin,

Grab a wiring diagran and try to follow your problems there. Cleaning the grounds is step #1 and there are a few of them. Undo them and sand the connections so that they make a good earth/ground. This can solve many issues right off.

[Fraser]

Dustin,

There are 3 wires (If I remember correctly) under the tank which plug into the wiring loom. These need reconnecting and crimped firmly into place, they often give a strange reading to the fuel gauge/light if loose.
The temperature gauge can take 1 hour before moving, depending on where you are riding and outside temperature. The gauge will not move after starting the bike and leaving it idle (unless you have very little oil!).
Cheers, Fraser.

[dross1]

Thanks!! I am going to work on it tomorrow; getting my new tire so I will have my day full of work on the bike. I won't mess with the temperature gauge then. I'll ride it for a while and see if it starts to move any (seeing as how most I do is 15 min of traveling between 30-45 mph).

[streetsurfer]

I'm picturing this scenario, if this is the first time you've filled the tank since purchasing and it sat empty for any amount of time.

Perhaps the float arm on the sending unit was stuck in the empty position. Fresh gas slowly dissolved any gum that had formed and freed it up, and your guage went from empty to full. Float may have a leak in it, and as it filled with gas it again sunk and showed empty. Could be why it was left unplugged--so previous owner would not rely on false reading.

You might drain the gas if needed and inspect that the sending unit's float arm is free to move within the tank without rubbing on the side, and is bouyant and not filled with gas.

[higgy]

plastic floats always leak,it is just a matter of time...............you can drain them and seal them if you have skills, or make your own.... a little brass from the local hobby shop and some solder and of course the time.it only needs to hold an equivalent volume of air or N2 and be of the same mass.

[dross1]

The man I bought it from said he had a problem with the float. So my friend and I took a look at it, since we were cleaning the carb out. Turns out it was in working order and that was when I noticed the unplugged wire. Though with the way it kinda flickered (the gas light), I assumed it could be the wires itself. I will take another look at the float and double check it. Worst case scenario is I have to fix it... just more work for me

Much thanks!!

[Mc tool]

Yeah Frazer is on to it . There are 3 wires , one is the earth and the other 2 are the wires for the low fuel light and the gauge itself.I spent ages dicking about with the float thing but I could never get it to tell the truth all the time . If I got it to read correctly at low fuel , upon filling I could ride over 100km's b4 the gauge started to drop ( plummet more like it ), or the other way it said empty at 1/3 tank. Ha , Once I tip toed down the west coast thinking I was dangerously low on fuel, stress ,worry .....rolled into Haast thinking I was lucky to make it ,and the -uckin' thing still had at least 6-7 litres in it

[Tamburinifan]

Not uncommon is that the part between float & wires (forgot its name...) is faulty.
When wires are connected, the fuel light is constantly ON.

[dross1]

I cleaned the wires and crimped everything back into place. When I have the tank at a 60 degree angle it reads about half tank. I watch the float move around and everything seems to work. Soon as I give it a slight move, back to empty it reads. I followed the wiring diagram and made sure everything was working, which it was. Though I am at a loss again. Float moves as the gas moves so that is doing its job.

There are 2 copper (at least to me they look copper) wires that run from the inside of the tank to the outside. They are attached to the float mechanism on the inside of the tank. Could this be my problem in that those wires have gone bad??

Much thanks!!

Dustin

[higgy]

Not uncommon is that the part between float & wires

It is a variable resistor(wire potentiometer) and sounds like it has a short and will need to be replaced,repair can be done but it not really practical. I have plans to take my spare tank apart and look into a reliable replacement if it is at all possible, they are made pretty cheaply.

[dross1]

How can you replace those? Is there an easier way to remove the system from the inside of the tank? I took off the gas cover and had enough to fit my one hand in. I figured I would wait till this tank runs dry and then mess with it.

Do you happen to know if there is a way to replace only those wires or is it too difficult to get them?

Thanks for the help!

Dustin

[streetsurfer]

The sending unit is mounted to the tank from underneath.
To remove it would mean removing the tank. Have you already addressed these under tank connections? Maybe it's a weak ground on the sending unit.




I would reach in through the top and operate the float arm while watching the light and gauge.
It hinges through the white plastic piece, I think. Swing it through it's full range, gently and repeatedly and see if the response of the gauge or light gets better. If so, maybe some contact cleaner sprayed internally around the sending unit would help clean the contacts in the rheostat or potentiometer and restore it's proper operation.
I haven't had the sending unit apart, only swapping it out in a tank change once, but my thoughts are, as it's up out of the gas in an idle tank, and unless the tank is regularly sloshed around, I guess it could be possible for varnish or corrosion to form on connections in there. Since it works sometimes or partially at least, maybe it just needs a good cleaning (and of course verifying good connections).

[dross1]

Thank you for the pics!! I am close to empty on my tank so work will be done within a day or two. I am wondering if corrosion caused it because sitting for a few years and never really having a full tank at times; perhaps something went wrong.

I will find out that's for sure!! :-D

[dross1]

After taking a few good looks at your pictures you posted and looking at my tank, I have realized that I did not clean the contacts very well on the underneath side of the tank. I am going to take it apart saturday, pull out the float and all, and see if there is something wrong internally (after I clean the contacts better). I have been slacking since I went back to college and being 4 hours away from the bike for this week is stalling my work phase. Hopefully I can try and solve this mystery saturday. I was upset... filled it straight to the top, went 2 weeks on the tank, and the guy I bought it from said he would get 150 miles to the tank. I was bone dry at 125 miles...

Needless to say I pushed the bike to the gas station (4 miles) and filled it up there. The man said it was a 4.5 gallon tank, but I filled it from bone dry to top in maybe 5.2 gallons? Does this sound right or did I overfill it???
I get nervous on it now when I reach 100 miles on a tank, because I have no idea whether I could make it 50 miles, 40, 20, etc...
Do you have a rough idea of how many miles your paso gets to the tank and to the gallon? I want to start using the paso for road trips because it is suppose to be better on gas than my truck is... but I can't stop and fill it ever 125 miles, 150 would be more ideal

Thanks everyone!!