Fuel gauge

[mt308]

Hi

This is probably a really basic question...

Trying to calibrate my fuel gauge. When full I get about 7 ohms of resistance. Empty seems to be about 180 ohms or so. This is taking a reading between the sender unit and an earth connection.

BUT when I turn the ignition on the readings go crazy. The empty tank shows infinite resistance (i.e. I can't get any reading at all) and the full tank shows about 165ohms.

Is this normal, or might I have some sort of short circuit going on.

Am I taking readings between the right wires?

As it stands my fuel gauges are not accurate - they read full when full, but when they lose about 10 litres they read about 1/4 full.

I have standard VDO tube sender units, Ultima supplied.

Thanks
Mark

[Graham-P]

I believe it's due to the shape of the tanks you will get an empty reading even though there's half a tank still available. I have a SPA digital dash and took reading every 15 litres, I could only get 72-73 litres in so I guess there was a little in the bottom plus the sponge.
Tank empty 68 ohms
15 litres. 48 ohms
30 litres. 38 ohms
45 litres. 34 ohms
60 litres. 19 ohms
73 litres. 6 ohms

There is a gizmo you can fit from a company called Spiyda Design that converts the signal for odd shaped tanks.
https://www.spiyda.com/magento/index.php/vehicle-e...
HTH

[Ultimike]

Is that link correct? I would love to get my fuel tank readings more accurate. I max at about 55 litres when my tanks show empty.

[845ste]

but gtr have original tank 27 liter each, for a total of 54l.
it's wrong?
mine have 27+27

[Graham-P]

Ultimike said:

Is that link correct? I would love to get my fuel tank readings more accurate. I max at about 55 litres when my tanks show empty.

I think this is the one that reads fuel level and more
https://www.spiyda.com/magento/index.php/vehicle-e...

845ste said:

but gtr have original tank 27 liter each, for a total of 54l.
it's wrong?
mine have 27+27

Ultima fuel tanks are 40 litres each, but mine (2007) are filled will foam so some capacity is lost.

[Ultimike]

Graham-P said:

Ultimike said:

Is that link correct? I would love to get my fuel tank readings more accurate. I max at about 55 litres when my tanks show empty.

I think this is the one that reads fuel level and more
https://www.spiyda.com/magento/index.php/vehicle-e...

845ste said:

but gtr have original tank 27 liter each, for a total of 54l.

Will this only work with a digital dash or will it also work with the standard fuel gauges?
it's wrong?
mine have 27+27

Ultima fuel tanks are 40 litres each, but mine (2007) are filled will foam so some capacity is lost.

[845ste]

Ultimike said:

Is that link correct? I would love to get my fuel tank readings more accurate. I max at about 55 litres when my tanks show empty.

also I have filled them with sponge (now after 15 years I have to replace it with a new sponge): I tried to fill them and we are about 27 liters each.
probably in 2001 they contained up to 27l
boh!

[mt308]

Thanks all

I have the gauge wizard which I have to date nstruggled to calibrate. However I think I will add another earth connection as I have 4 spade connectors on the back of the fuel gauge which might be too much....

Have just taken readings for a standard 40 litre Ultima tank which were as follows from a VDO sender unit.

Empty 73.8ohms
1/4 65.4
Half 51.7
3/4 29.0
Full 9.8

Will let you know if I can calibrate using the wizard. Ran out of time tonight.

Mark

[F.C.]

Fuel gauge Resistance copied from my notes.

L - Ohms
0= 72
2= 68
4= 65
6= 62
8= 59
10= 55
12= 53
14= 50
16= 47
18= 44
20= 40
22= 37
24= 32
26= 28
28= 23
30= 17
32= 11
34= 2

[Ultimike]

Assume this wizard/method works with standard non digital gauges?

[Steve_D]

Ultimike said:

Assume this wizard/method works with standard non digital gauges?

Yes it does.
Are you asking if it will work with digital?

Steve

[Ultimike]

Not digital. Standard gauges only many thanks.