Fuel tank sender voltages

[MarkWebb]

Drove the Canam for the first time today!
The car has a motec SDL dash and the first thing I noticed was that the fuel readings are complete rubbish. Bearing in mind the strange shape of the tank has any body actually measured the voltage on the sender with various levels of fuel in tank? The Motec and many other electronic guages would be able to use this data to give accurate fuel remaining figures.

[DHGTR]

Hi Mark

The fuel sending information is actually a resistance measuring in Ohms.
Each set up will be slightly different so i dont know if the readings i input to my SPA dash would be any good for your car.
The most accurate way would be to empty your tanks and add a certain amount of fuel whilst measuring the resistance reading on the sender. The amount of readings would depend on how many segments you dash needs. Eg if your dash will handle 5 segments then if each tank holds 35 litres, you need to add 7 litres take the reading, then add seven more, take the reading, etc etc etc ...... also dont forget you need an empty reading as well.

Dave

[MarkWebb]

Thanks Dave. I would agree that the reading should be ohms. (I am an electriciian) I am not sure how your display works but the Motec has a calibration chart where you can input data to correspond to the levels. This data is then shown as a calibration curve. The more data you input the more accurate the curve is. Presently it seems to be measuring a voltage and the calibration seems to have been input as a full reading and an empty one. I guess I need to talk to somebody who knows Motec stuff.
Not sure (having not built the car) what type the fuel senders are etc or if they need any adjustment when fitted (some do) but the differences that you talk about will also be present between the two tanks in my car. I can only use one calibration chart so some compromise will be required.
Yor data would certainly be a starting point.

[rduart]

Please see emails attached below. Message from Richard. I had the same question.

• ***********************8

Ted/Richard can you tell me the ohms readings for the fuel level sender when empty and full. I need to program my dash display. I ended up going with RacePak.

Please advise,

Thank you,

Randy

• **********************

Hi Randy,

Full 2.1ohm
Empty 71.9ohms

Happy New Year from all of us at Ultima.


Best Regards


Richard

• **************

Thanks,

Randy

[MarkWebb]

rduart. Thank you that is a start. however those 2 figures will produce a linear tank reading between thode 2 readings. because the tank is a non linear shape you will not get correct readings between those points.

[MHunter]

I'm having a problem with the fuel gauge. When the ignition is off, the needle lies below the zero mark, as it should. When I turn the ignition on, the needle moves a bit, but doesn't pass zero. I checked the resistance for both tanks, and got 54 ohms and 69 ohms at the tank sender. I checked the 3-way fuel switch and got the same readings on the wire going to the gauge. There's only 2 ways to wire the gauge (VDO or CAI), and the other way the needle doesn't move at all.

Any ideas?

[pilbeam_mp62]

MHunter said:

I'm having a problem with the fuel gauge. When the ignition is off, the needle lies below the zero mark, as it should. When I turn the ignition on, the needle moves a bit, but doesn't pass zero. I checked the resistance for both tanks, and got 54 ohms and 69 ohms at the tank sender. I checked the 3-way fuel switch and got the same readings on the wire going to the gauge. There's only 2 ways to wire the gauge (VDO or CAI), and the other way the needle doesn't move at all.

Any ideas?

Sounds like an issue with the sender - Did you remove the little pins in the senders before installing them ?

Regards

[Steve_D]

MHunter said:

.....I checked the resistance for both tanks, and got 54 ohms and 69 ohms at the tank sender. .....

If those reading are full and empty (or vice-versa) then I would say the gauge is dead. Does the gauge itself require an earth connection and is it good.

Steve

[MHunter]

Both tanks have some fuel in them. Wouldn't 54 ohms be in the range stated in the email by the factory above? then the gauge needle should be somewhere between 0 and full, no?

I'll try to vary the amount of gas in one tank, and see what happens. I'll also take out the sender and make sure I removed the pin.

[MHunter]

Steve_D said:

MHunter said:

.....I checked the resistance for both tanks, and got 54 ohms and 69 ohms at the tank sender. .....

If those reading are full and empty (or vice-versa) then I would say the gauge is dead. Does the gauge itself require an earth connection and is it good.

Steve

The gauge does need an earth. It is the same wire as all the other gauges, but I'll make sure it is ok.

[pilbeam_mp62]

Steve_D said:

MHunter said:

.....I checked the resistance for both tanks, and got 54 ohms and 69 ohms at the tank sender. .....

If those reading are full and empty (or vice-versa) then I would say the gauge is dead. Does the gauge itself require an earth connection and is it good.

Steve

Steve,

I read that as meaning he got those readings for BOTH tanks - not full and empty on ONE tank.....