Fuel gauge output scaling question

[Hemi2slow]

Has anyone ever messed with the fuel gauge output on their vehicles? I have always been aggravated by the fact that the fuel gauge in my 04 truck doesn't read linearily. It stays on full for a while then moves on to half a tank rather quickly then below a half a tank it drops really fast. Its just aggravating. So I decided to mess with the settings in the fuel sender and gauge output tables. What I'm wondering is if I did it right. I took the gauge output table interpolated between 100 and 10 percent since it was not a linear curve. Then I took the primary volume gauge table and interpolated it between 0 and 100. I did the same in the primary volume table.

Now, what I'm wondering is if I did this right. I don't want to run out of gas on the side of the road because I messed it up. What has got me wondering is that I noticed that the tables seem to be reversed from what they should be. The description in the software of the primary volume and the primary volume gauge tables says that they are remaining fuel volume versus remaining fuel level from sender. But the data in those tables seems to be reversed. The remaining volume numbers are higher at the lower level indicators and decrease as the level indicators increase. So they are inverted. The gauge output table is the same way. The PWM value is higher at a lower gauge percentage and decreases as the gauge percentage increases.

Does anybody have an explanation for this? Also, did I scale the values in the correct manner? Thanks in advance for any info.

[mecanicman]

no idea but would love hear your results.

[Hemi2slow]

Well I'm currently in the process of testing it. I can say this, the fuel gauge isn't moving as fast now. Not sure if that is a good or bad thing. Main thing I'm worried about is making sure that when the gauge says empty I still have a couple of reserve gallons left.

[almostfast]

well this thread is only 2 months old, I'm trying to mess with my fuel gauge in my S10, It always used to stay on full for like 4 days straight and then the last 100 miles of the tank the gauge would plummit.

my situation is weird because I have an 18.5 gallon tank where the engine/pcm, and (I THINK) sending unit are from a 16.9 gallon trans am tank.

I have no Idea if I'm getting anywhere or not, I tried making a fuel level gauge in the scanner, but it says I still have 17.6 gallons left after driving 25 miles. thats like 30mpg. I never get better than 21 on the highway, AND I was beating on it for most of the 25 miles.

I changed the fuel tank capacity in the tune to 18.5 and I tried rescaling the primary and secondary levels from 0-18.5 gallons.

watch me run out of gas because I screwed it up. lmfao

[TheThickster]

same here my bro in laws v6 sierra isnt marking correctly when its at a 1/4 tank its empty what can I do to fix this? besides messing with the settings of course.

[almostfast]

same here my bro in laws v6 sierra isnt marking correctly when its at a 1/4 tank its empty what can I do to fix this? besides messing with the settings of course.

pull the fuel sender assembly out of the tank and bend the float arm?

[TheThickster]

pull the fuel sender assembly out of the tank and bend the float arm?

I guess we could do that but wouldnt we need another fuel pump to compare it to?

[almostfast]

I guess we could do that but wouldnt we need another fuel pump to compare it to?

I wouldn't think so, just eyeballing it should make the difference.

[almostfast]

well I think I finally made some progress here. the table im working with is primary volume vs. level.

it still takes some figuring, you need to know exactly how much gas your tank will hold and how much you have in it at any given time. I've been using this lame config I made to see what the PCM thinks it has for fuel in it and adjusting the primary volume table accordingly.

this config has a fuel volume remaining gauge in it. for example it was reading 18.16 gallons left with an actual volume of 14.65gal in the tank, so I changed the cell in the primary table with the 18.16 to 14.65, then interpolated it between the horizontal bounds of it and where it hits zero.

then I filled the tank back up to a full 18.5gal, which brought the gauge up to 16.2, so I did the same thing again, except this time interpolating between it and the 14.65 that it was at earlier. every value after that full mark should be whatever your full volume is.(in my case 18.5 gallons) I'm going to try it at 3 gallon increments and it should end up pretty close.