BroncoII4x4.com

Hi all: Newbi here. I've got a 89 2.9 4X4. The gas gauge will not read full when fully tanked up. I suspect a loose wire somewhere but the other dash gauges also read "funny". Could these be inter-connected somehow? Any suggestions or fixes? Thanks for your time, Wayne.

in the past manufacturers have used a 2 peice sensor that reads from empty to half and then from half to full, it might be a sending unit on mine it only works when it is raining or extremely damp which tells me that it is in the wiring, im not desperate enough to fix it yet and the sensor and float is 120.00 at oreilleys.

tickturd wrote:in the past manufacturers have used a 2 peice sensor that reads from empty to half and then from half to full, it might be a sending unit on mine it only works when it is raining or extremely damp which tells me that it is in the wiring, im not desperate enough to fix it yet and the sensor and float is 120.00 at oreilleys.

Oh really?

Show me a picture or a reference to it from a Ford manual..
This must be amazing cause I never heard of that one before!!

I haven't either. The fuel guages have a tiny wire wrapped around a non metallic piece that makes up the sending unit, as the float moves up and down it changes the signal to the guage, thus moving it. It's all a matter of resistance.
If there is a gap in the wiring, of if that particular spot is corroded, it will throw off the guage. If the wire is broke, I belive the guage won't work at all.
I drive truck for a living, and the fuel guage in my truck will go crazy at about 3/4 of a tank till it gets to a little less than 1/2. The wire in the unit is tweaked, and that is the spot where it acts up.
Easiest is to replace it unless you want to live with the guage.
Another possibility is the guage is not moving all the way up or down whichever the way of travel it is. If you can, pull it out and check for binding.

this page was started Mon Mar 22, 2010,it is now Wed Jul 21, 2010

either its fixed or they don't care

The guage on my 90 B2 would not work. It wouldn't even move when the key was turned on so I decided to install a new sending unit. Since I am painting the mid section I decided to take the bumpers off and the tank skid plate. In preparing to install the unit I emptied the gas and then couldn't get a sending unit for a month so I filled the tank up again and guess what? The guage now works. It must have been caught or stuck and lowering it all the way must have cleared it. Hope it keeps working.

My '85 gauge acts funny too. It shows full but once it gets to 3/4 it quickly goes to empty even though I have plenty of fuel.

I see pulling a fuel tank in my future.

"G"

ConductorX wrote:My '85 gauge acts funny too. It shows full but once it gets to 3/4 it quickly goes to empty even though I have plenty of fuel.

I see pulling a fuel tank in my future.

"G"

I have an 86 B2 that acts the same way as yours. I haven't heard from very many people that have a working gas guage. I think it was a design problem.

I bet the after market like Speedway or Painless have gas gauges that work.

An IVR (Instrument Voltage Regulator) can effect the gas gauge but it will effect other gauges also if bad (temp, oil pressure). Most of the time it’s the sender but sometimes it’s a connection or ground. The main body ground comes off the Battery to the Radiator core support. As with any Voltage problem there is no “this is it “ solution most of the time. Check out the attachment. I lucked out with my gauge problem cause my lift pump went out and when I replaced it (it came with sender) my gas gauge started working. This wiring diagram is for a 88, later models may be different. Happy Ohms law.

Hi all: I haven't answered as I have been busy. However, I am going to check the ground by the rad. Yes some of the other gauges are also affected so maybe this is more common than I expected. Wayne.

I was doing some research, and I used to own a 72 Maverick with a 302 with auto, and my guages would act weird, and my gas gauge was always wrong.
There is a wire that runs from the battery to the ignition switch that had a built in resistor, and if that resistor went bad, it would screw up the electrical circuit.
It was a pain in the ass to find, and once I did, I replaced it, and it worked fine till I wrapped it around a phone pole.
I'm not sure about the newer rigs if they still had that in the wiring. Electrical gremlins are a pain to find.