fuel guage

[padre]

my fuel guage seems to run in reverse. pulled sending unit out and when i raise the float the guage goes to empty and then full when i lower it. 2017 vintage guages,in tank pump.ffr rf wiring harness. any suggestions appreciated

[Papa]

Have you calibrated it? With the sender that comes with the kit, you need to set the calibration to 7/8 full mark to match the ohm values for the gauge (16-158 ohms). If in doubt, remove the sender from the tank and check the resistance with an ohm meter to be sure it's functioning.

[initiator]

I think Papa's got it - there is one calibration for reverse-acting senders. Mine came with the correct calibration, but I've heard that's not always the case.

[padre]

never replied to thread so hope this gets viewed. sender works but reacts backwards. how do i calibrate it? do physically adjust something?

[Papa]

never replied to thread so hope this gets viewed. sender works but reacts backwards. how do i calibrate it? do physically adjust something?

Padre,

Check the instructions packaged with the gauges. You'll need the reset button plugged into the gauge and then with power to the gauge press and hold the button to enter calibration mode and then press the button repeatedly until the needle is in the position for the 16-158 ohm range. If I recall, this is at the 7/8 full position. I don't recall if you need to do anything more to store the new calibration.

Dave

[chmhasy]

look for your fuel gauge they have instructions

https://www.speedhut.com/

[padre]

found calibrator button. i have some gas in tank. will that change the precedure in any way? thanks

[Papa]

found calibrator button. i have some gas in tank. will that change the precedure in any way? thanks

It won't. Once calibrated, the gauge should reflect the proper reading for what's in the tank.

Dave

[MisterAdam]

Dont expect pinpoint accuracy. Mine reads 7/8 when full then sits there for awhile. Then it will drop to below 1/2 rather quickly and bounce around. My coyote gets 24 mpg so i just reset tbe tripometer and fill every 250 miles.

[edwardb]

Dont expect pinpoint accuracy. Mine reads 7/8 when full then sits there for awhile. Then it will drop to below 1/2 rather quickly and bounce around. My coyote gets 24 mpg so i just reset tbe tripometer and fill every 250 miles.

Something going on there. I've had several of the Speedhut fuel gauges with the kit provided sender. All have worked fine with nothing like that going on. My guess is your sender isn't working properly. But wiring and gauge are also possibilities. It's a pretty simple circuit.

[Papa]

Padre,

Not sure if you found your instructions, but here they are:



Note that the factory default is 240-33 Ohms, which is probably why your gauge was reading in reverse.

[MisterAdam]

Something going on there. I've had several of the Speedhut fuel gauges with the kit provided sender. All have worked fine with nothing like that going on. My guess is your sender isn't working properly. But wiring and gauge are also possibilities. It's a pretty simple circuit.

Hmmmmm. Been like that from the beginning....2015. Maybe i will try a new sender. Thanks, this gives ne somehing to do....all i have been doing is driving.

[2bking]

My fuel gauge does the same, never over 7/8 full with fuel up to the top of the fill tube. I replaced the sender once thinking it was the problem and done the calibration routine several times. I've thought about bending the float arm to make it read full but then it would read 1/8 tank when empty. As it sits, there's about a gallon of fuel left when it reads empty.

[Papa]

Hmmmmm. Been like that from the beginning....2015. Maybe i will try a new sender. Thanks, this gives ne somehing to do....all i have been doing is driving.

My fuel gauge does the same, never over 7/8 full with fuel up to the top of the fill tube. I replaced the sender once thinking it was the problem and done the calibration routine several times. I've thought about bending the float arm to make it read full but then it would read 1/8 tank when empty. As it sits, there's about a gallon of fuel left when it reads empty.

Have you guys considered the manual calibration steps in the instructions? You could customize the calibration to your situation.

[edwardb]

Have you guys considered the manual calibration steps in the instructions? You could customize the calibration to your situation.

Good point and will be curious to hear how that works. Disclaimer: I was mainly responding to the words "bouncing around" which sounded like something wasn't working right or maybe intermittent. The gauge will move some with movement of gas in the tank. So maybe it's OK, including supporting comments from 2bking. Just hasn't been my personal experience. When full, my gauges have shown full. When they get to empty, do typically have 1-2 gallons left, which is fine. I usually fill at the 1/4 reading. For grins, these are notes I made when checking the gauge on my #7750 build. Speedhut gauge and kit supplied sender, set on 16-158 ohm calibration.

Put in 5 gallons (measured from pump at Shell) in one gallon steps using cleaned out milk jug. Observed fuel gauge after each gallon:
1 gallon = No indication. Not off peg.
2 gallon = Halfway between 1/8 full and bottom line
3 gallon = 1/8 full
4 gallon = 30% past 1/8 full toward 1/4 full
5 gallon = 70% past 1/8 full toward 1/4 full
True 5 gallon (e.g. balance of fuel can, 1/4 - 1/3 gallon) = Just below 1/4 full.

[2bking]

Have you guys considered the manual calibration steps in the instructions? You could customize the calibration to your situation.

Well, good point, but originally I was thinking the sender was at fault or the 7/8 fuel calibration point wasn't correct. After I verified the empty reading was really an empty tank, the full mark wasn't so important. I get to drive 50 miles with a 7/8 full tank before it starts dropping. Manual calibration requires a full tank and an empty one and access to the back of the gauge. I'm having fun driving with a fuel gauge that really indicates empty so manual calibration isn't high on the todo list.

[MisterAdam]

Well, good point, but originally I was thinking the sender was at fault or the 7/8 fuel calibration point wasn't correct. After I verified the empty reading was really an empty tank, the full mark wasn't so important. I get to drive 50 miles with a 7/8 full tank before it starts dropping. Manual calibration requires a full tank and an empty one and access to the back of the gauge. I'm having fun driving with a fuel gauge that really indicates empty so manual calibration isn't high on the todo list.

I tried the manual calibration once but that just caused errors on the full end instead of the empty. One problem i have is i am not sure of tank capacity....i think 14 gallons. Also i do not want to go too low for i am afraid of burning up pump. maybe i will try the manual cal again.

[edwardb]

I tried the manual calibration once but that just caused errors on the full end instead of the empty. One problem i have is i am not sure of tank capacity....i think 14 gallons. Also i do not want to go too low for i am afraid of burning up pump. maybe i will try the manual cal again.

Fox body Mustang owners manuals list the tank as 15.4 gallons.

[MisterAdam]

i burnt a fuel pump up go-carting so i am a little gun shy and never go below 1/4 tank

[Boydster]

...I get to drive 50 miles with a 7/8 full tank before it starts dropping...

Would this be because of the taller section of the tank that has to be burned off before the sender gets its first chance to start dropping?

[2bking]

Would this be because of the taller section of the tank that has to be burned off before the sender gets its first chance to start dropping?

Yes, the tall section has two or three gallons in it and the float is below in the larger part of the tank.

[MisterAdam]

So now i think mine is dead. Stays at 3/4 and i have traveled 150 miles. My plan is to pull the sending unit out this weekend but how do i test it? I can put a 12v source to it and make the float but what should i be measuring?

[Murd]

Measure resistance in ohms at empty and full

[Papa]

So now i think mine is dead. Stays at 3/4 and i have traveled 150 miles. My plan is to pull the sending unit out this weekend but how do i test it? I can put a 12v source to it and make the float but what should i be measuring?

No power to the sender, just test resistance across the two contacts as you move the float between the full and empty positions.