Please Help - Fuel level?

[Dreamtool1]

Hi everyone! Hope there is some electical genius here that can help me!

This is the case... My Yamaha fz6 was parked for the winter and all was fine, but the day when I should start it in the spring the battery was dead (so I replaced it) and when I got the bike running I recond that the fuel gauge has gone crazy!

When i filled the whole tank up full it shows almost full (one unit from full), and when the tanks goes towards 3/4 full the tank meter drops to nothing and "empty tank" is blinking with no steps in between)

So sensor fault? I took it out from the tank and measured Ohms and got from 23-Ohms to 140-ohms (steplessly), wich i guess are a good sign??

So what can it be? Have anyone had any similar problem?

 

[FinalImpact]

Hi everyone! Hope there is some electical genius here that can help me!

This is the case... My Yamaha fz6 was parked for the winter and all was fine, but the day when I should start it in the spring the battery was dead (so I replaced it) and when I got the bike running I recond that the fuel gauge has gone crazy!

When i filled the whole tank up full it shows almost full (one unit from full), and when the tanks goes towards 3/4 full the tank meter drops to nothing and "empty tank" is blinking with no steps in between)

So sensor fault? I took it out from the tank and measured Ohms and got from 23-Ohms to 140-ohms (steplessly), wich i guess are a good sign??

So what can it be? Have anyone had any similar problem?

Excellent troubleshooting there.... However, If i had to guess, its the wires that got pulled from the connector or something like that.

In this electrical section is a sticky for places to order parts and in the tech section a how to troubleshoot and repair. Take a look here.

FUEL TANK, FUEL PUMP, AND FUEL GAUGE

The black wires are common ground to both the pump motor and fuel gauge. They should measure as a short or Zero ohms between them (see white and green connectors). Look at that thread, post up if ya need a hand.

[ame="http://www.amazon.com/dp/B00JDIDQN8"]FZ6 Fuel Pump[/ame] and Fuel Sender Connections:
The WHITE connector w/ Green/white trace is for the fuel level sensor and the GREEN connector w/ Red/Light Blue trace for the fuel pump (larger gauge). Black wires are chassis ground on both connections. Use your OHM meter to verify ground is ground. Inspect both wires for strain damage. If you have a variable resistor (see link above), place it between the sensor conductors and see if the fuel gauge reads empty and full when adjusted. ((Roughly the same VALUES the stand alone meter reported))..

 

[Dreamtool1]

Hmm interesting! I can surely admit that the cables are a bit short when you flip up the tank... and when the battery was dead, there was a lot of lifting and i guess putting strains on those cables... And if i even remember correctly the white one is the shortest of those two!
Will definitively check ground tomorrow... Is there any other easy accessible "orher end" of that white cable where i can plugin the resistor so i eliminate any fault/cuts in the wire?

Thanks so much for now... Will update on my progress!

 

[TownsendsFJR1300]

Agreed with the fuel gauge wire likely being pulled and a poor connection.

If you can, leave the rear fuel tank hinge bolt in (remove the front inner fairings for clearance) and you'll be much less likely to pull those wires and have more control lifting the tank.

Either a piece of wood or a paint mixing stick works well at holding up the tank (tighten up the rear hinge bolt ith the tank up to keep the tank from flopping back and forth)..

Please post back what you find..

 

[Dreamtool1]

Ok update...

So this is what the cables looked like... I don't know, but i think they seam quite good actually. I can't tell If there is any damage to them anyway.
View attachment 56537
View attachment 56538

I also measured the black wires (green and white connector) for any resistance and that gave me a short circuit value of 0.4 Ohm due to bad connection to ohm meter else it seams like a good short. (also measured the connection between them and it gave me a 1.0-clear connection)

Moving on... I then followed up by connecting some oms in the white connector and got an confusing results...

At low resistances
22-60 omhs I got flashing empty tank OR flashing fault in wireing. (8 flash empty/full)
~100 Ohms gave a clear "reserve fueltank" left. (flashing low)
100-138 ohms gave me Nothing! Just wireing fault (8 flashes empty/full)
(How i attatched my resistances)
View attachment 56544
I didn't have a 140ohm, so that is 100+22+15 soldered together and measured with ohm meter.

Though I know that if I fill the tank up with fuel and connect the tank meter it should show one unit from full. (have done this for the past 3 tanks) which makes me confused.
Why doesnt the gauge react the same to my resistances as it does with the OEM fuel meter? In My world 140 ohms through the fuel sensor or 140 ohms with resistance is the same! But apparently not...

I then continued to measured the volts of the fuel gauge which gave me 12.02v which i guess are the correct signal voltage...

So... I'm stranded again.
I hope this is solveable since i have a trip to Isle Of Man TT in a month and it would be a pain in the ass to refuel at every gas station for 3000km

 

[FinalImpact]

Re: Please Help - Fuel level? // +1 for level of confusion!

Although you have valid ohm values (resistors) and readings, I still have to wonder if the wires strands are compromised.
- Do you have a 12V test lamp? Unlike an ohm meter a small test lamp can verify the wire can carry current. Place one lead to Battery Positive and the other to the senders black ground wire. Lamp should light. This would tell us the ground is intact!

The green sensor wire is a voltage source from the gauge cluster. That said, unplug the gauge cluster and ohm the green wire from Cluster to Sensor! Be sure to do a wiggle and pull test. It should handle a small strain and not pull apart or change values.
- Also, there is an intermediate plug in the fairing. Verify its not corroded at either point or compromised. If the bike is stored outside, I've repaired a gauge cluster from damage. The whole connector was compromised - SO THIS DOES HAPPEN!

If both of wire section check out, you might need to pass current through the GREEN WIRE using the same principal as the ground wire test. Be very careful selecting the green/white trace wire ONLY ((UNPLUG ECU TO BE SAFE))!! Isolate wire at both ends (unplug). Ground one end of green wire to battery. Insert 12V Test Lamp in the other end and connect the other lamp lead to +12V Battery. Lamp should light if wire conducts energy. EDIT: You could use a flash light battery and bulb for this test too!

My fear is the wire strands are broke while the wires sheath or jacket is whats holding yours together. Lamp Test will verify this! As for the readings: The resistor values used should work unless they introduce an intermittent connection.

If need be, you can remove the conductors from the connectors. Look inside and you should see a tiny tab to depress on the female conductor (not sure which side, it may be covered by rubber plug).
If not a tab to depress, sometimes a small brass tube can be slid over the conductor body to depress the lock which allows the conductor to be removed from the connector housing.
You're doing a great job TS and I can see why you'd be shaking your head!

 

[Dreamtool1]

Re: Please Help - Fuel level? // +1 for level of confusion!

Ok, looks like I will take a look at this after work! Will have so search for that green/white/striped wire behind the gauge cluster then, hope it's pretty easy accessible on the S1 model too.
But this "Also, there is an intermediate plug in the fairing" I guess you are talking about something under the right fairing by the seat with the fuses? My bike is currently stored inside but in a cold garage with high humidity and variating climate... Batteries often gets corroded to the point that cars do not start in this climate so that part is intressting! ... What exacly is it i should be looking for? A relay?

This is worth gold... To have someone that have such great knowledge helping fellow riders out, can't stress this enough!

 

[Motogiro]

...Since the supply current for these reading will be relatively low(sensor in fuel) I wonder if the sensor supply voltage could be diverting to ground through the tank. This might account for discrepancy with final gauge readings even though resistance tests are in the norm... Measure for resistance to the tank? Also the wiper assembly is submerged in fuel. Could there have been a conductive contaminant?

Sent from Moto's Motorola

 

[Dreamtool1]

Re: Please Help - Fuel level? // +1 for level of confusion!

Although you have valid ohm values (resistors) and readings, I still have to wonder if the wires strands are compromised.
- Do you have a 12V test lamp? Unlike an ohm meter a small test lamp can verify the wire can carry current. Place one lead to Battery Positive and the other to the senders black ground wire. Lamp should light. This would tell us the ground is intact!

The green sensor wire is a voltage source from the gauge cluster. That said, unplug the gauge cluster and ohm the green wire from Cluster to Sensor! Be sure to do a wiggle and pull test. It should handle a small strain and not pull apart or change values.
- Also, there is an intermediate plug in the fairing. Verify its not corroded at either point or compromised. If the bike is stored outside, I've repaired a gauge cluster from damage. The whole connector was compromised - SO THIS DOES HAPPEN!

If both of wire section check out, you might need to pass current through the GREEN WIRE using the same principal as the ground wire test. Be very careful selecting the green/white trace wire ONLY ((UNPLUG ECU TO BE SAFE))!! Isolate wire at both ends (unplug). Ground one end of green wire to battery. Insert 12V Test Lamp in the other end and connect the other lamp lead to +12V Battery. Lamp should light if wire conducts energy. EDIT: You could use a flash light battery and bulb for this test too!

My fear is the wire strands are broke while the wires sheath or jacket is whats holding yours together. Lamp Test will verify this! As for the readings: The resistor values used should work unless they introduce an intermittent connection.

If need be, you can remove the conductors from the connectors. Look inside and you should see a tiny tab to depress on the female conductor (not sure which side, it may be covered by rubber plug).
If not a tab to depress, sometimes a small brass tube can be slid over the conductor body to depress the lock which allows the conductor to be removed from the connector housing.
You're doing a great job TS and I can see why you'd be shaking your head!

Update!!

Ok, so today i took the headlamp off and measured the wire... first with ohm, (0.4ohm/1.0 Clear connection) which was fine.
Any corrosion that could have been in the connector was scraped of the best i could, though I really don't think there was enough corrosion in there to cause any problem just some sand and dirt that fell in when i took the connector appart. Anyway, this is what the connectors in both the male and female contact looked like (both ends of the cable)
View attachment 56558

Moving on... I connected a 12v lamp to the wire in one end and battery positive in the other and the lamp lit up just fine (couldnt get any pictures cause I had way to few hands) I couldnt tell any difference in ammount of light between battery -->Lamp -->GND OR Battery -- > Fuel sensor wire --> Lamp -- GND.
The pulling and pushing on the wire did no difference nither.

So back to square one... I'm really starting to wounder if my gauge cluster took any damage when the battery went dead in the motorcycle in the winter. Soon that's is going to be the only thing left.

But where is the connector that was "located under the fairing"? Is there one more connector in the S2 model inside the gauge? Cause the S1 only looks like this...
View attachment 56559

Just a thought...Since the supply current for these reading will be relatively low(sensor in fuel) I wonder if the sensor supply voltage could be diverting to ground through the tank. This might account for discrepancy with final gauge readings even though resistance tests are in the norm... Measure for resistance to the tank? Also the wiper assembly is submerged in fuel. Could there have been a conductive contaminant?

Sent from Moto's Motorola

Good thinking there... I looked this up, and found out that Petrol actually have a conductivity of about ~320pS/M which actually makes it a low partial conductor. but that shouldnt be enough to have a noticable difference to the ground itself. I also measured the resistance from sensor meter in the tank --> Tank itself and it gave me no resistance and no clear connection. Even the connection from Ground in bike to ground in tank was quite bad (430 conection value, not a good conductor) due to rubber bushings i guess.

Though I talked to my local Yamaha repairshop and they said that the fuel can cause some ohm differences when measuring the sensor meter. I.e submerged in fuel may not read the same as it would in dry conditions due to short distances between resistors in the meter. Though this doesn't seam to be the problem in my case.

 

[TownsendsFJR1300]

Just curious, was the fuel tank full over winter or ?

I ask in that is it possible for corrosion to build up on the electronic, in tank unit causing a bad connection?

Might not be a bad idea to pull the tank and pump and check the float switch directly. (you could also clean out any crap that does accumulate in there over time).

 

[Dreamtool1]

Just curious, was the fuel tank full over winter or ?

I ask in that is it possible for corrosion to build up on the electronic, in tank unit causing a bad connection?

Might not be a bad idea to pull the tank and pump and check the float switch directly. (you could also clean out any crap that does accumulate in there over time).

The tank was about 1/4 full when I placed it in the garage for the winter, or that is how much it was in the tank this spring anyway. The sensor and pump was the first thing i disassembled cause that's usually what goes wrong. And cause Sweden acually have a really high cleaning standard of fuels everything looked like new, and could not see any corrosion or crap built up in nither sensor or connectors. Everything acually looked really clean even the fuel filter was perfect... The sensor anyway read clear 23-140ohms outside tank which it should.

 

[TownsendsFJR1300]

I suspect you have the tank back together...

I was going to suggest plugging in the fuel sending unit (W/O the tank), turn on the ignition and see how the gauge re-acts with float arm movement.

Its kinda odd for that to fail just sitting...

 

[Dreamtool1]

One step ahead of you I actually just forgot to type that... Since it was such a pain to get the pump out if the tank I tried all possible scenarios. I could not read the ohms while i was testing it with the ignition on that was not really crucual...

W/O tank with the sensor attatched and ingnition on there was just the same results as there was when I put fuel in the tank and drove.

With fully lifted sensor arm (full tank) the meter showed 1 unit from full...
Lowering the arm slightly gave me 2 units from full
Then there was no steps in between that and empty (flashing reserve tank)
And lowering the arm towards the bottom stop the tank went for "electirical fault flashing" (8 flash full/empty)

Though the strange thing is that I can not replicate full tank with my resistors (137ohms)
it just flashes for "electrical fault" but when meter is attached i get 1 unit from full... Strange...

Edit. My next step will be to go buy some fuel and refill the tank so the tank is full again to measure the ohms of the sensor in the tank once again when the sensor is submerged in fuel i guess. And see if I can get the "one unit from full" senario replicated.

 

[TownsendsFJR1300]

With fully lifted sensor arm (full tank) the meter showed 1 unit from full...
Lowering the arm slightly gave me 2 units from full
Then there was no steps in between that and empty (flashing reserve tank)
And lowering the arm towards the bottom stop the tank went for "electirical fault flashing" (8 flash full/empty)

Though the strange thing is that I can not replicate full tank with my resistors (137ohms)
it just flashes for "electrical fault" but when meter is attached i get 1 unit from full... Strange...

Edit. My next step will be to go buy some fuel and refill the tank so the tank is full again to measure the ohms of the sensor in the tank once again when the sensor is submerged in fuel i guess. And see if I can get the "one unit from full" senario replicated.

Electrical, is NOT my strong point. However from what you post above, you get a signal (one notch down from full), then another notch, then nothing then another signal once the arm is bottomed out.

The one notch down could simply be the float arm bent slightly on the low side.

***Can you see, when you initially turn the key on, the actual dash LEDS for the fuel level come on? IE, several LEDS not working?

That would confirm all the LEDS good in the dash.

If that works, you can rule out the dash. I'd be leaning towards that actual gauge as your getting a signal from the fuel gauge albiet, its not fully correct.

The tank, as noted above is rubber mounted so all your wires have your ground included. I don't know if there's a frame ground and if so, where.

Just some thoughts to kick around. Good luck.

 

[Motogiro]

The tank, as noted above is rubber mounted so all your wires have your ground included. I don't know if there's a frame ground and if so, where.

Good thought! ^^^^ FinalImpact also said to check this in post #2

Could it be that the ground (black wire) in the sensor is not at full ground? In other words could the black wire be electrically floating above full ground? To prove this out run a jumper from the the sensor black wire to the negative lead on the battery and redo your float range test. If it cures the problem there is a poor ground either to the chassis/engine or at some other point.

 

[TownsendsFJR1300]

I, way back, bought a new 1989 red Corvette. At times the A/C stopped working, arghhhh.

Turned out to be the self tapping screw, FOR THE GROUND WIRE self tapping screw INTO THE FRAME, for the A/C WASN'T TIGHTENED DOWN fully.

The Wire end would float up and down on that bolt, sometimes grounding, sometimes not. Easy fix once they found it. Someone was lazy on assembly back then..

 

[TownsendsFJR1300]

Good thought! ^^^^ FinalImpact also said to check this in post #2

Could it be that the ground (black wire) in the sensor is not at full ground? In other words could the black wire be electrically floating above full ground? To prove this out run a jumper from the the sensor black wire to the negative lead on the battery and redo your float range test. If it cures the problem there is a poor ground either to the chassis/engine or at some other point.

Probably not related (same train of thought) but Yamaha outboard engines, especially wiring thru to sensors, the ECU etc, will ALWAYS have 12 volts to it.

It'll adjust say the idle sensor(ICV), etc with the ground. Same for oil pumps (2 strokes) high pressure FI fuel pumps, etc.

 

[Coltczt]

Old thread! But i have exactly same problem and have looked every where and looked with ohm meter, and its something inside my dash that is the problem.. Gonna live with that and use tripmeter. Its so frustration to see it blinks after 90km or something!