Fuel gauge issue

[badmix]

Ill try and explain as best as possible. For the longest time , if I filled my tank to the top, the gauge would read way past the F mark. Well, a couple weeks ago I actually ran out of gas, I knew it was going to be close but I didnt make it home in time, got within 2miles, lol. Anyways at the time my fuel gauge was on the notch just before the E mark.

So, now ive been trying to "gauge" how my fuel gauge will react etc.

I never got to totally fill the tank since then but had driven it to where it went low on the fuel gauge. Basically, it was at the notch before E and then I started filling it up, it took 22.95 gals to fill it. Now the line is just barely over the Full mark. So, my question is can a Fuel sending unit actually "RESET" itself and start reading properly or should I keep an eye on it.

My speedo is 20mph off due to gear change and taller tires, so trying to judge my mileage is hard to do. I get about 8-10mpg Im guessing.

Also, how much does the fuel pickup miss? Im guessing there is 1/2 to 1 gal left in the bottom.

Anyways, just thinking outloud and want to get ideas or comments on this.

Thanks.

For those that need visual reference, lol

 

[Fordum]

Actually its the tall tires and gearing that is screwing up the gauge too.
You need to take all that off......

OK, some of the newer gauges use the sending unit to give a miles to empty reading, so the computer gets involved that much, but thats about it.

Other than that, its still pretty much the same system that has been around for years.
Wire wound resistor in the tank, with a wiper arm that moves across it as the gas level changes.

So, if anything changed, it would most likely be the sending unit.
I'm not sure just exactly how it would make the change you say. Usually it either quits working completely, or goes dead past a certain level.

What seems to have happened is that it picked up a little extra resistance somewhere.
Maybe there was some crud on the last part of the wiper travel and it picked it up.
If that were so, I would expect that it would wipe off after a while.
So, for now, I would just keep an eye on it.

One trick I do, is to reset the trip odometer at each fillup. I work out how far I can drive under normal conditions and when I start getting close to that distance, I start looking for a station.

When I was younger, I fooled around a lot with calibrating gas gauges.
I used variable resistors, voltage divider networks, even plotted the differences in resistance of the sending unit of my Jeep with a half full tank at different angles.

Filled 2 legal pads with measurements and calculations. My idea was to build a system with weights and potentiometers to compensate for whatever angle my Jeep was parked at.

Came to the conclusion that it could not be done.
Today, with a small PLC or computer, I could do it.

But, now its not worth the effort.

As far a correcting a gauge that reads offset from correct like your did, the best way I have found is to fill the tank completely, and then bend the needle until it is dead on the full mark.
This will usually get the empty mark pretty close.

 

[badmix]

I thought about bending or moving the needle.

I dont have a trip odo thingy on my truck. its an 84 K5

 

[Fordum]

I dont have a trip odo thingy on my truck. its an 84 K5

Time for a GPS

 

[badmix]

I use GPS to verify my speed. Luckily my speedo is exactly 20mph off. So if it reads 85 , im doing 65

 

[4X4HIGH]

Just pull the sender and verify that it reads from 0-90 ohms. If it doesn't then replace the sender and the gauge will read correctly. FWIW i'm running 35" tires, 4.56 gears and have a HOT 355 and I only get between 240-270 miles on a tank before i'm needing to add fuel to make me feel safe. My fills ups usually consist of about 27-29 gallons.

 

[badmix]

I can go about 260 miles on the freeway with 4:11s, 33s, 700r and 305 with high miles. Ive got a Holley 570cfm carb and dual exhaust, I know these things are big bricks so I dont expect much.

260miles is running from full tank to fumes, lol. give or take