Fuel Gauge Not Working

[JeepGuy]

This weeks issue... (I may sound like I'm complaining, but I actually love this stuff).

So, Brand-new painless wiring harness, Brand-new fuel gauge, Brand-new sending unit (actually the third brand-new) and the gauge is not moving at all. The wiring was installed was completed about a year ago at this point and the gauge has never moved. Painless Bronco Specific kit. I always figured it was bad sending units in the tank which I've had to replace for leaking issues, but at this point I figure it has to be the gauge.

Reading on here I found this regarding the Ohms that the sending unit is supposed to be putting out... 73 empty and 10 full. Should that measurement be read at the sending unit from the two posts? Or is there a place on the actual gauge (behind dash) where I could measure this? For reference, all other gauges work on the stock cluster so I'm pretty sure it's not an issue with grounds at the cluster.

When I wired this, I connected the ground wire to the post side of the sending unit (outside the tank) that is blank on the backside/inside. Meaning, the other post appears to connect inside the tank to a yellow wire that goes down to the metering unit inside the tank, as is run up to the gauge,

Ground wire was run up to the body where I sanded down to bare metal before mounting.

Any recommendations here?

 

[Oldtimer]

At the tank, connect the wire going to gauge to ground. Zero ohms should peg the needle in guage at full.

NOTE: On a stock Bronco, the only wire connected between frame and body is the tank ground wire.

 

[JeepGuy]

At the tank, connect the wire going to gauge to ground. Zero ohms should peg the needle in guage at full.

NOTE: On a stock Bronco, the only wire connected between frame and body is the tank ground wire.

I'll give this a shot today.

 

[Broncobowsher]

The other overlook is the ground from the body (the body is where the gauge is at and completes the loop) to the sending unit.

If grounding the wire going to the sending unit to the body pegs the gauge full, you just proofed from that connection to the gauge is all working. Need to chase the sending unit to the body ground.

Other questions that are likely to creep up. Does the factory temp and oil gauges work? This could point to a failure in the instrument voltage regulator.
If everything is checking out as working (for the gauges except fuel), grounding the sending unit didn't peg the guage, the temp and oil work. Try putting the fuel gauge wire on the temp gauge. Check again. The temp gauge acts the same as the the fuel gauge (different face and values but under it works the same). This can help tell if the actual gauge itself is bad.

 

[JeepGuy]

The other overlook is the ground from the body (the body is where the gauge is at and completes the loop) to the sending unit.

If grounding the wire going to the sending unit to the body pegs the gauge full, you just proofed from that connection to the gauge is all working. Need to chase the sending unit to the body ground.

Other questions that are likely to creep up. Does the factory temp and oil gauges work? This could point to a failure in the instrument voltage regulator.
If everything is checking out as working (for the gauges except fuel), grounding the sending unit didn't peg the guage, the temp and oil work. Try putting the fuel gauge wire on the temp gauge. Check again. The temp gauge acts the same as the the fuel gauge (different face and values but under it works the same). This can help tell if the actual gauge itself is bad.

All other gauges in cluster work fine.

I tested the ohms on the freshly replaced sending unit in tank. It's a around half full and it read 56 - 57 ohms.

Switched wires as suggested above, no change at gauge.

Checked ohms reading at back of gauge still mounted in cluster... Nothing.

Checked Volts to the black and white wire and it read 5

Tried connecting sending unit wire (orange) to ground and nothing changed.

Checked all fuses, nothing bad.

I'm guessing either I somehow messed this thing up during install, or it was simply just a bad gauge. Been a few years since I bought it, so I'm not worried about trying to get a free replacement. New one is already ordered and on the way. If that doesn't work, I will revert to the old math and odometer reading along with a jerry can and a few extra gallons of fuel onboard every time I drive it anywhere.

 

[gnpenning]

Check the orange wire for continuity between the gauge and sending unit.

 

[Viperwolf1]

Does it have the tank switch on the dash? It may be in the wrong position, may not be working, or may be wired wrong.

 

[JeepGuy]

Check the orange wire for continuity between the gauge and sending unit.

I checked that and got a 0 reading at both ends of the sending unit wire. I want to say it's yellow but would have to check the book for confirmation.

Does it have the tank switch on the dash? It may be in the wrong position, may not be working, or may be wired wrong.

I removed the aux tank and eleiminated the switch. When installing the painless harness they give you specific instruction on two wires that are crimped, heat sunk together if only running one tank and I double checked that too. It's all good and done according to the instructions.

New gauge should be here in a couple days. My plan is to get on it as soon as it shows up.

 

[Broncobowsher]

Check the orange wire for continuity between the gauge and sending unit.

That's what it sounds like to me as well.

When you say you get a 0 reading at both ends, this doesn't make sense with a sending unit that does have a ~50 reading.
Put a ground on the body to the meter, don't move it. Keep that as a reference point that stays put.
Take a reading at the sending unit, should be ~50 as you state.
Connect the wire under the truck
Go under the dash, check the other end there. Should be ~50 as well. It doesn't sound like that is happening. Which would put the problem with that wire, not the gauge

 

[JeepGuy]

New gauge installed... TOTALLY SHOCKING... Still nothing.

I double checked the instructions in the painless harness for eliminating the dash switch for tanks. No issue there, everything done as planned.

Went to the rear, installed another ground to frame instead of body and removed the body ground to the tank hoping that was the issue. Even sanded off the paint so there is a very clean connection. No change still no reading.

Set the multi meter on the 200 upside down horseshoe looking thingy which I believe is for OHM???

Took the wiring connection off the tank sending unit. Used the mulit meter prongs black to ground side, red to sending unit side. Reads just 51.something. Moved the ground off the sending unit to the frame where I installed the new ground. Reads 51. something.

I put the wiring harness connection back on the tank sending unit ensuring its connected. Get to the back side of the gauge. I put the black on a body bolt for ground and touched the red wire to the sending unit side on the back of the gauge. Reads the same as the tank... 51. something. I leave the ground where it is on the body, and move the read wire to the "I" side of the gauge where the black wire that reads 5V's coming in is installed. Key is still off, Ohm read 60+ something on that side.

Turn the key on. Multi meter black wire is still on body bolt for ground. I switch the multimeter to the 200 reading with the V - .. which I believe is for checking DC voltage. Touch the read wire to the "I" side of the gauge and it reads 5. Touch the red wire to the "S" side of the gauge and it reads 6.something.

Actual gauge never moved.

Left the key on, went back to the tank. Removed the sending unit plug and ran a wire from the sending side of the plug to the ground side of the sending unit and Holy Shizzznitttttss the gauge went to full. Only positive I've had with this gauge today.

Other then that...I still don't have a fuel gauge that reads anything.

I'm at a loss here.

 

[Broncobowsher]

OK, we have progress. Gauge reads full when you ground the sending unit wire at the fuel tank. That just proofed the wiring from the tank to the gauge is good as is the IVR.
The only thing left is the sending unit and/or the ground to the sending unit.

FYI, frame grounds are generally a bad choice. The electrical system is with the engine and the body. Both of those are sitting on rubber mounts to the frame.

 

[JeepGuy]

OK, we have progress. Gauge reads full when you ground the sending unit wire at the fuel tank. That just proofed the wiring from the tank to the gauge is good as is the IVR.
The only thing left is the sending unit and/or the ground to the sending unit.

FYI, frame grounds are generally a bad choice. The electrical system is with the engine and the body. Both of those are sitting on rubber mounts to the frame.

I just switched the ground back the body. Clean bare metal. No change at the gauge. I think this Bronco just refuses to have a working Fuel Gauge.

 

[DirtDonk]

Or the overseas manufacturers refuse to make a working sending unit anymore.

 

[Brush Hog]

Haven’t people had sending unit floats that had holes in them and they filled with fuel and never rose with fuel level? Leading to gauge always reading empty. Think the sender can be installed with float arm upside down too but that causes constant full reading if I remember correctly. Not sure if the ohms test rules that out as a problem. If not I’d take sender out and wire it to gauge and move arm around and see what gauge does.

 

[DirtDonk]

Exactly! If you have it out again for any reason, or get another one, definitely connect the wires to the sender before you install it.
Run it through the sweep with somebody watching the gauge, or some way to hold the float arm in different positions while you go up and turn the key on to see what happens.

 

[Broncobowsher]

I recently had an issue with another project vehicle. The sending unit worked. But not in the tank. Come to find out the silver metal was actually painted metal. The sending unit was grounded to... paint. Talk about a head scratcher. It worked, but didn't. Had to meter every bit of the sending unit to find the layer that I didn't know was a layer. Metal on metal wasn't really metal on metal.

 

[JeepGuy]

Haven’t people had sending unit floats that had holes in them and they filled with fuel and never rose with fuel level? Leading to gauge always reading empty. Think the sender can be installed with float arm upside down too but that causes constant full reading if I remember correctly. Not sure if the ohms test rules that out as a problem. If not I’d take sender out and wire it to gauge and move arm around and see what gauge does.

The thing I hate more than electrical is removing and or installing a sending unit in a stock Bronco tank. For now, estimated 11 gallons per mile on a full tank with pictures of the odometer at fill up as a reference will be my get down.

 

[SLOWnEASY]

OK, we have progress. Gauge reads full when you ground the sending unit wire at the fuel tank. That just proofed the wiring from the tank to the gauge is good as is the IVR.
The only thing left is the sending unit and/or the ground to the sending unit.

I had to read this entire thread multiple times to comprehend where you are on this. But I think Broncobowsher is correct. Your new sending unit in the tank is faulty. Or the ground from the sending unit to the frame is faulty.

 

[JeepGuy]

A win is a win people. No idea what changed. I put this all back together and just conceded that this Bronco really does not want a working fuel gauge.

Then there I was. Out on a leisurely drive through a local neighborhood and look down to see the gauge has moved. Not only moved, but is probably pretty accurate. I toped the tank completely off a day or two ago and have put probably 50 or 60 miles on it since.

I have zero clue why it's working, but I won't be complaining about it.

 

[BroncoJimbo]

Mine has been on "works when it wants to" mode for years. It seems worse when it's cold outside.
I'm glad you got yours working.