Fuel level calibration

[Gregconboy158]

Hi, I'm planning on using a windows tablet as my main dash, this is getting rid of the original clocks. Do we know if possible and if so how to do so to add fuel level to the g4+ ecu? It's a Honda PnP if makes a difference. 

 

I have the ohms readings for full, half and empty. 

Please let me know if it is possible or not 

 

Thanks, 

[Adamw]

You will need to wire an external pull up and an RC filter to damp to signal from the fuel sloshing around.  See the bottom of this post for an example:

 

You can then set the analog input up as a GP input and use a cal table to scale it 0-100%

[cj]

This should do roughly what you want. The values wont be used for any calculation but it would be enough that you could output it on a gauge in pclink.

Obviously swap in your own values for ohm readings -> percentages. Also note that the raw value off these sensors is quite jumpy as the fuel sloshes around. I dont think there is a way to dampen them in the software but you can do it with some external electronics.

 

[Gregconboy158]

Thanks for the replies lads! Always a great help on this forum! 

 

My fuel sender readings are 

270 ohms empty, 65 ohms (approx) 1/2 tank, 15 ohms full.

 

Will the diagram on that post still be ok for mine Adam? 

[Adamw]

16 hours ago, Gregconboy158 said:

Will the diagram on that post still be ok for mine Adam? 

Yep, the 100ohm pull up will give you roughly a 3V range so that will be good.  Make sure the resistor is at least a 1/2W size, the circuit will be pulling about a 1/4W when the level sensor is at 15ohm so would probably fiz a 1/4w resistor.

[Gregconboy158]

Right had a chance to try this out, for some reason I can't get it to read though lol. I've wired as per the pictures you put on that other thread Adam and here are my settings and all it will read is 0% lol. Have i done something wrong? I'm not with the car currently but these are the values stored into the ecu. 

[Richard Hill]

Try the input units as volts.  See what reading you get empty and full.  (Ideally  If the sender is not in the car, just move the float from min to max to test and read off the raw voltage ) 

[Adamw]

Correct, it is not going to work with the cal table input in ohms - this calculation only works for a 1K pull-up.

[Gregconboy158]

Thanks for replies lads. I will have to try get the sender out of the tank and measure the readings in volts. Fingers crossed it comes out! 

[Richard Hill]

You don't have to pull the sender, that just makes it easier to work out the full voltage swing to check the potential divider values are correct.

  I always calibrate with the sender in the tank.  With a partial tank of fuel I disconnect the union at the fuel rail and pump the fuel into a container until the fuel pump draws the last pure fuel.  That voltage is empty.  Then add in 5 litre increments until full, noting the voltage at each point.

HTH,

Richard.

 

 

[Gregconboy158]

I got it working using ANVOLT4 on my PnP ecu. 

What I was wondering was, can I use ANTEMP instead though? I've got 3 spare ANVOLT on the expansion loom which I've currently used all of and I need another! If I had known it had so little 96-98 civic PnP instead of the 95! As that has an extra 3 ANVOLT over my one. 

 

If it isn't possible to use the ANTEMP for it, is there any way of adding more ANVOLT at all or is that just not possible? 

 

Thanks, 

[Richard Hill]

If you're not using narrow band lambda you could nick the analogue volt for that off the main ECU header plug...

The problem with temp. Inputs is they have an internal pull up resistor which is quite a high value, which will result in a low reading.  If you can work around this then yes, although the calibration will show temperature, I guess you could create a custom calibration and ignore the temperature units. Calibrate as  a percentage or maybe litres.

HTH

Richard.

[Gregconboy158]

On 1/13/2019 at 10:12 PM, Richard Hill said:

If you're not using narrow band lambda you could nick the analogue volt for that off the main ECU header plug...

The problem with temp. Inputs is they have an internal pull up resistor which is quite a high value, which will result in a low reading.  If you can work around this then yes, although the calibration will show temperature, I guess you could create a custom calibration and ignore the temperature units. Calibrate as  a percentage or maybe litres.

HTH

Richard.

Thanks for your reply Richard, I think I'll leave it as ANVOLT for now. 

Do you know why when I put the readings in of 0,50,100 it autocorrects to the nearest whole number? 

Example of mine is;

0.64v - 100%

1.96v - 50%

3.64v - 0% 

 

It will change it to 

0.6v

2v

3.6v

 

Anyway on stopping it doing this? 

 

Thanks, Greg

[Adamw]

Use cal table 1, 2 or 3

[Gregconboy158]

Thanks Adam I was using cal8. Will try it on either of them today and report back. 

[Gregconboy158]

Anyone able to shed some light on this for me please. 

 

My fuel gauge stopped working a while ago after some welding on the car (this is what I put it down too) finally got round to redoing the wiring today and it seemed to work ok at first but then started acting erratically and if you move the wiring around the resistors and capacitor it will fluctuate between 0%-50%, sometimes not reading anything sometimes jumping up and down, sometimes just a lower reading. 

 

I have the capacitor and sender using earthed to chassis not sensor ground, if this makes a difference and it is wired per the diagram above

[cj]

Grounding any sensor to the chassis instead of the ECU sensor grounds is not ideal. It means the sensor will have potentially have a different level of what "ground" means, and an therefore give incorrect reading (ie it might be say 10 or 20% high or low). Its usually pretty consistent however with how wrong it is. 

What you describe is just a wiring fault. One of either - wires coming apart, wires shorting to each other, or wires touching the chassis. The fact you can reproduce it by wiggling wires in a specific spot means you even know where the fault is. you need to re-join/re-solder/fix the connections in that area and also make sure there are no exposed wires that can bump into each other or ground to the chassis. 

[Gregconboy158]

14 hours ago, cj said:

Grounding any sensor to the chassis instead of the ECU sensor grounds is not ideal. It means the sensor will have potentially have a different level of what "ground" means, and an therefore give incorrect reading (ie it might be say 10 or 20% high or low). Its usually pretty consistent however with how wrong it is. 

What you describe is just a wiring fault. One of either - wires coming apart, wires shorting to each other, or wires touching the chassis. The fact you can reproduce it by wiggling wires in a specific spot means you even know where the fault is. you need to re-join/re-solder/fix the connections in that area and also make sure there are no exposed wires that can bump into each other or ground to the chassis. 

Thanks for reply cj, I think I might potentially know what the problem is! I didn't realise (or look tbf) that the capacitor has to go s certain way +/- and I think it might be round the wrong way so going to look at that today and change out the capacitor if it is infact wrong and will report back. 

 

Shall I change to sensor ground then? On both capacitor and sender or just one? 

[Adamw]

Yes, if you are using a polarised cap it will need be connected with the correct polarity.  However, that is not your problem if the reported fuel level changes when you wiggle the wires - As CJ said above, and I said in your similar facebook post, it is a bad connection.

Sensor ground would be preferable provided your fuel level sensor does have its own dedicated ground pin.  Many dont and just ground via the fuel tank so you have to use chassis ground in that case.

[Gregconboy158]

All sorted, capacitor was round the wrong way, my bad lol. Put new one in right way and all is fixed and well, no more erratic readings. I will put the earths to sensor ground when I get a minute. 

[Kenneth Yu]

On 2/24/2019 at 12:38 PM, Adamw said:

Yes, if you are using a polarised cap it will need be connected with the correct polarity.  However, that is not your problem if the reported fuel level changes when you wiggle the wires - As CJ said above, and I said in your similar facebook post, it is a bad connection.

Sensor ground would be preferable provided your fuel level sensor does have its own dedicated ground pin.  Many dont and just ground via the fuel tank so you have to use chassis ground in that case.

Hey @Adamw Quick question. Since i am still using my stock Nissan dash fuel gauge, can i just pull a 2nd wire from the fuel sender? By putting 5v down on the 2nd line wont it electrify the entire chain back to my stock dash?