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Discussion Starter · #1 ·
Hi there, 2013 Daytona 675R. I'm running a fiberglass tank, so the guage isn't fitted. That gives a malfunction error for the gauge and consequently the fuel light stays on. I checked the resistance in the gauge and it's between 12 ans 112 Ohms full to empty. So, I thought 'I'll put a resistor in a wire to the gauge plug on the bottom of the pump'. Fitted a 68 Ohm resistor in series to the black wire. But the error code and light remain.


I'm wondering if I need to fit the resistor across the terminal that the gauge plugs in to? It plugs in to the pump. That's inside the tank in fuel though.


Can anyone help with ideas? Am I correct in my thinking? It's probably an unusual enquiry as not many people will be running alternative tanks.


Thanks anyway for any help.
 

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Try this...measure the voltage between the black/green wire and ground(black wire).

The voltage is important because this will allow us to calculate the power dissipated by the 68 ohm resistor. That's important because it will then allow us to size the resistor correctly (power wise).

When you have measured and posted that voltage we will move on to step two.

I believe the black wire is ground and as such wiring a resistor in between this wire and a plug (if I understood your post correctly) won't help you. I'm still not clear where the other end of this wire goes. It sounds like it plugs into nothing.
 

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Discussion Starter · #3 ·
Thanks for the reply. I'll measure the voltage tomorrow and post back. Is that with ignition on? Also, should I measure both with and without the resistor?

I didn't think it would matter which wire I used as it must complete a circuit? Part of the circuit must (I presume, go through the ECU, to check the resistance and display the fuel level on the dash and turn the light on when fuel is low). Bear in mind that electrics are my weak point (not that I have any strong ones! He he).
 

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Thanks for the reply. I'll measure the voltage tomorrow and post back. Is that with ignition on? Also, should I measure both with and without the resistor?

I didn't think it would matter which wire I used as it must complete a circuit? Part of the circuit must (I presume, go through the ECU, to check the resistance and display the fuel level on the dash and turn the light on when fuel is low). Bear in mind that electrics are my weak point (not that I have any strong ones! He he).
Yes, ignition on and bike handlebar switch set to run.

I would do the following based on my assumptions, which are included..

Assumptions:
There is a 2 wire connector going into the tank for the fuel level. There is nothing connected to the other side of that connector since you no longer have a fuel level sensor. One wire is green/black and the other wire is black. You cut the black wire and put the 68 ohm resistor in series with that wire before it reaches the connector.

Here is how I think the fuel level circuitry works. It's a simple voltage divider and the fuel level sensor changes voltage based on fuel level. The ECU reads this voltage and displays the voltage as a fuel level.

Easier if you draw a picture. Draw a horizontal line about 2" long. Name this line Vp(voltage from power supply). Draw another identical line 1" below the first. Name this line Vfl(voltage fuel level). Draw a third line 1" below the second. Name this line Gnd(ground).

Now draw a resistor between line Vp and line Vfl. The size of this resistor is X since we don't know what the size is. This is called a pullup resistor.

Now draw a variable resistor between line Vfl and Gnd. This is your fuel level sensor resistance that changes based on fuel level.

Vp goes to a power supply of unknown voltage.
One side of the Vfl line goes to the fuel sensor. The other side of Vfl goes into the ECU which reads the voltage on the Vfl line.

If you have connected the resistor as described above, then connect a wire across that connector, shorting the two pins. You should see a fuel reading. But don't stop there. We need to know the voltage across that resistor. You need to connect the red lead of your voltmeter on one side of the resistor and the black lead on the other side of the resistor and take a reading.

This will allow us to figure out the power being dissipated by that resistor. This is important because resistors have power ratings and we want to know two things. One is that the resistor can dissipate the power without burning up and the other is that the resistor won't get hot enough to start melting things like wires and fuel lines.

Although the following is not necessary for what we are trying to accomplish, you're there, so why not.... unshort the two pins in the connector. Then connect the red lead of your voltmeter to the G/B wire. Connect the black lead of the meter to the end of the resistor away from the connector (this will ensure that the resistor is not in the circuit). Note the voltage.

I will say that for this application, the higher the resistance of the resistor the better, within reason. 112 ohms is nearly twice 68 ohms so using a higher value resistor would be better for what you are doing. Let's worry about that after the tests above are completed.
 

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Could this be solved by a variable resistor?
I'm sure it could be, but I don't think we will gain anything since a variable resistor that isn't moving is the same as fixed resistor from the viewpoint of the ecu. A fixed resistor is more reliable and smaller, all things being equal, so likely is the better choice for this application.

The reason for the tests above is that I want to calculate the minimum power rating that the resistor should be so bad things don't happen.
 

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Discussion Starter · #7 ·
Ok, back again. I get 5V at the connector. Have attached a couple of pics of my resistor set up. The picture of the pump is a Sprint one for ref. It has a ball/cock gauge not the tube type. But you can see it has it's own wee connector that goes on to the pump body, so inside the tank and fuel. If I assume correctly; there is also some kind of circuit/gizmo in the pump and coupled to this circuit we're looking at, that operates the low level fuel light. Which I believe is independant of the gauge.


As mentioned in my first post, I'm wondering if I just make up a resistor/plug that plugs into the body where the gauge plugs in? It would have to totally fuel proof though, which is my main concern.


Thanks again.
 

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Ok, back again. I get 5V at the connector. Have attached a couple of pics of my resistor set up. The picture of the pump is a Sprint one for ref. It has a ball/cock gauge not the tube type. But you can see it has it's own wee connector that goes on to the pump body, so inside the tank and fuel. If I assume correctly; there is also some kind of circuit/gizmo in the pump and coupled to this circuit we're looking at, that operates the low level fuel light. Which I believe is independant of the gauge.

As mentioned in my first post, I'm wondering if I just make up a resistor/plug that plugs into the body where the gauge plugs in? It would have to totally fuel proof though, which is my main concern.

Thanks again.
Check your PM.
 

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Ok, back again. I get 5V at the connector. Have attached a couple of pics of my resistor set up. The picture of the pump is a Sprint one for ref. It has a ball/cock gauge not the tube type. But you can see it has it's own wee connector that goes on to the pump body, so inside the tank and fuel. If I assume correctly; there is also some kind of circuit/gizmo in the pump and coupled to this circuit we're looking at, that operates the low level fuel light. Which I believe is independant of the gauge.


As mentioned in my first post, I'm wondering if I just make up a resistor/plug that plugs into the body where the gauge plugs in? It would have to totally fuel proof though, which is my main concern.


Thanks again.
Ok, back again. I get 5V at the connector. Have attached a couple of pics of my resistor set up. The picture of the pump is a Sprint one for ref. It has a ball/cock gauge not the tube type. But you can see it has it's own wee connector that goes on to the pump body, so inside the tank and fuel. If I assume correctly; there is also some kind of circuit/gizmo in the pump and coupled to this circuit we're looking at, that operates the low level fuel light. Which I believe is independant of the gauge.


As mentioned in my first post, I'm wondering if I just make up a resistor/plug that plugs into the body where the gauge plugs in? It would have to totally fuel proof though, which is my main concern.


Thanks again.
Manxkiwi,
I just got the error code you mentioned on my triumph sprint. It seemed to be related to the same issue you had in the fuel level. Did putting the resistor in the fuel gauge electrical line work in eliminating there error code?

If so, would you be able to send anothe pic (I cannot see the line) and the resistor for you used. I see the pic you originally posted, but I couldn't tell how you connected it.

TIA
CH
 

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Discussion Starter · #10 ·
Manxkiwi,
I just got the error code you mentioned on my triumph sprint. It seemed to be related to the same issue you had in the fuel level. Did putting the resistor in the fuel gauge electrical line work in eliminating there error code?

If so, would you be able to send anothe pic (I cannot see the line) and the resistor for you used. I see the pic you originally posted, but I couldn't tell how you connected it.

TIA
CH
Hi Crazyhorse. The inline resistor didn't work, well didn't stop the light, so didn't do what I wanted. I ended up making what you see in the attachments, I think it's a 68 Ohm resistor and it seemed to survive in the tank/fuel. I scored a lightly damaged spare tank, so I'm running that now with fuel gauge fitted, so as stock. I sold the glass tank.

If I recall correctly? This stopped the error light, but you obviously have no gauge and (I think) the low fuel light didn't work. Though I'm not 100% on that as it was some time ago and I don't really remember. It was fine on the track bike as you're always checking and topping up fuel through the day.

Hope this helps? Is your gauge broken?
 

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Manxkiwi,

Thank you for the reply.

Yeah, It was running fine, then I guess I let them fuel run low. I registered it and it came on after the cooling fan started.

The fuel gauge isn't broken. What happens is the check engine light illuminates when the cooling fan kicks in. This in turn makes the fuel gauge go to empty. Once the fan stops, the fuel gauge goes back to normal, but then the check engine light remains until I reset it with the odb.

Frustrating

CH
 

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Discussion Starter · #12 ·
Hmm, sounds like an odd fault. Could be difficult to nail down, but if not letting the fuel get too low stops it happening, then thet will probably be your task from now on; to not let it get too low..
 

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Discussion Starter · #13 ·
Oops, read that wrong. Seems it's the fan kicking in causing the issue, not low fuel level.
Good luck finding the problem anyway..
 
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