Fuel sending units read WRONG time after time!

-
My mod to the fuel guage works. I will open a new thread with the details

Later"
As I sit here and think about it, Maybe my modification did nothing and the gauge alwas showed empty because it was neat empty. I filled it up and adjusted my mod to show the gauge of the fuel tank full.
As the tank empties I will monitor it and If I find my modification did indeed make a difference, I will post it.
Maybe I outsmarted myself. I will advise accordingly
 
Here's something that you might try. You might want to "burn" another sender so you have one to screw with.

Carry a can, do whatever, but "get to a place" where the tank is near empty. Drain it through the fuel pickup, on level ground, until you "get air."

Us a good multimeter and carefully measure the resistance of the sender.

Go to a closeby station and fill clear up, drive home, and again on level ground, carefully measure the sender resistance.

You can access this at the rear harness connector in the kick panel if it's easier than crawling under.

Then drive the car or otherwise empty the tank, and yank out the sender.

Now build whatever you need for a jig so you can mount the sender with REPEATABLE results. Scrap wood, whatever

Now move the sender to get the measured resistances that you got above, and figure a way (vertical board, etc) that you can measure the float height and low point. This gives you the physical points of the float at MT and full.

Now with these physical points established, you can bend, lengthen, modify the sender to match as close as you can, the proper full/ MT resistances
 
Pawned said:
My mod to the fuel guage works. I will open a new thread with the details

Later"
As I sit here and think about it, Maybe my modification did nothing and the gauge alwas showed empty because it was neat empty. I filled it up and adjusted my mod to show the gauge of the fuel tank full.
As the tank empties I will monitor it and If I find my modification did indeed make a difference, I will post it.
Maybe I outsmarted myself. I will advise accordingly
Click to expand...

My 5vdc regulator bit the dust. I have pulled the cluster out and I am sure my previous 2 approaches based on variable resistors was the wrong way to go about it.
I am now working with a variety of voltage regulators. To control the voltages on the test bench I am trying to adjust the voltages. The 100 ohm resistors are 500 ohm resistors, I reread the labels, I did not buy the wrong resistors.
 
While my original gauge and sensors work well, someday I to may need to replace sender. My plan would be to use a small 50 cent micro controller, a few resistors and a MOSFET to accurately rescale the sender to the gauge for accurate measurement. The techniques suggested by 67Dart273 would be necessary to insure correct full travel. The micro would measure sensor resistance, and control gauge via PWM based on calibration table, or math translation. I have used this method for several sensor translators in industrial controls.
 
Try to use a brass, and not a plastic float, they are less prone to chemicals in the fuel these days. Also, many of the repro fuel sending unit resistor wires do not have the same number of turns of wire in them as the stock ones. I've noticed some of the Spectrum units have huge gaps between the strands of wires. I'd also do the upgrade to the solid state voltage limiter described on the allpar site. I did one for an E body and it works well, no issues with the fuel gauge reading. I managed to encase everything inside the case of a gutted factory voltage limiter so it plugs in just like a stock unit.
 
64ragtop said:
Or, send a PM to FABO member RedFish. (Unless you're just bound and determined to re-invent the wheel)

BC
Click to expand...

Thanks but no thanks. The OEM parts are nothing more than range indicators. If someone wants to update them to a more accurate instrument ... Good luck
 
You must log in or register to reply here.
-

Back
Top