96 Ranger Fuel Gauge Stuck at full

[Eaglefixer]

noticed my fuel gauge stuck on full to day driving back from Dr. Office. Hadn't have a chance to check it out yet so if anybody has any ideas where to start or check please reply.

Thanks

Steve

 

[Insanejughead]

Sounds like you've got one of those highly sought after and elusive "Mary Poppins" fuel tanks.


I wouldn't give it any thought. Just enjoy the fact that you don't have to stop by the gas station anymore.

(Try rocking your truck back and forth with a mostly full tank. The float could be stuck. That's all I can think of right now... )

 

[Eaglefixer]

ok, today just crawled under my truck to look for some wire connector and found a 16 pin connector just fwd of the fuel tank. Not sure what wires go to where. Does anybody have a wiring diagram for a 96 Ranger 4.0

 

[adsm08]

Sorry, left my 96 wiring book in my other pants.

The gauge wire is yellow and white though.

 

[Eaglefixer]

well disconnected the 16 pin connector just in front of fuel tank and grounded the yellow/white wire and the gauge stayed above the full mark and never moved.

Guess I'll order new sending unit and change the pump while i'm in there.

 

[Eaglefixer]

do i have a gauge problem or sending unit problem?

 

[RonD]

If you disconnected the Yellow/white wire and then turned on the key the gauge should be on FULL.

If you then ground the Yellow/white wire(the end going to the gauge, not the tank) the gauge will go to EMPTY(key still on)

If gauge doesn't do this then it is a gauge issue.
If gauge does go to full and then to empty it's a sending unit issue.

If you want to test the sending unit you will need an OHM meter, set it to scale 200
Put one meter probe on the Yellow/white wire going to the tank, put other meter probe on the Black or Orange wire going to the tank, one will be the ground for the float/sender, test both, diagram lists Orange but could be black.
Meter should show 16ohms to 160ohms.
16ohms is empty tank, 160ohms is full tank, so if meter shows 40ohms(almost empty) and you then filled up the tank and re-tested it would show 160ohms, 150ohms would be fine, these are guide line readings, not set in stone pass/fail.

 

[Eaglefixer]

Thanks Ron for the help. I'll check the sending unit tonight and report back on my finding. The tank is getting close to empty so it's a good time to check it and i will fill up tonight and check it full. If its the Gauge what do i need to look for if and when i take the the instrument panel out?

 

[Earl43P]

If you disconnected the Yellow/white wire and then turned on the key the gauge should be on FULL.

If you then ground the Yellow/white wire(the end going to the gauge, not the tank) the gauge will go to EMPTY(key still on)

If gauge doesn't do this then it is a gauge issue.
If gauge does go to full and then to empty it's a sending unit issue.

If you want to test the sending unit you will need an OHM meter, set it to scale 200
Put one meter probe on the Yellow/white wire going to the tank, put other meter probe on a good ground.
Meter should show 16ohms to 160ohms.
16ohms is empty tank, 160ohms is full tank, so if meter shows 40ohms(almost empty) and you then filled up the tank and re-tested it would show 160ohms, 150ohms would be fine, these are guide line readings, not set in stone pass/fail.

Small point needs corrected:

He'll HAVE TO use the pin for the BK/Y wire at the sender's connector to get a complete path. With the sender connector disconnected, there is no path to ground for the sender. If doing Ron's check from the Instrument panel connector, he is correct because the ground path will be intact.

The ground for the sender is way up behind the passenger kick panel, of all places.

Connect the YE/WH wire to the BK/YE wire at the sender plug for the easiest test.

 

[Eaglefixer]

Not 100% sure what your saying Earl, but this is what i think you may want to do. With the 16 pin connector disconnect at the tank I need to ground the BK/Y wire along with the Yellow and white wire to get the gauge to move?

 

[Eaglefixer]

OK now that i reread your post it makes senses now. I'll test again late tonight after i get back from the dentist and if it don't rain.

 

[RonD]

Small point needs corrected:

He'll HAVE TO use the pin for the BK/Y wire at the sender's connector to get a complete path. With the sender connector disconnected, there is no path to ground for the sender. If doing Ron's check from the Instrument panel connector, he is correct because the ground path will be intact.

The ground for the sender is way up behind the passenger kick panel, of all places.

Connect the YE/WH wire to the BK/YE wire at the sender plug for the easiest test.

Yes, thanks, I changed original post to include that.
Diagrams shows Black or Orange wire as ground, but black/yellow would fit better.

This is just to test the in tank sender/float.

 

[Eaglefixer]

ok, Got my truck bed up and moved aft just enough to get to the tank. I found a broke wire but i think i broke it removing the bed, only had my son helping me. Anyway got the wire soldered back together and disconnected the plug at the sending unit on top of the tank. I grounded the black wire and yellow/white wires and turn the key on and nothing happened to the fuel gauge. it remained stuck at full. Then i turn the key off and back on and now the fuel gauge went to empty! So i'm thinking its the sending unit. Can i get a second opinion please.

 

[RonD]

Now that the gauge is moving I would do the test, again.

With connector unplugged turn on key, gauge should go to full or empty, doesn't matter which way.
With key still on ground the yellow/white wire and gauge should go to the opposite end, either full or empty.
Unhook the ground and gauge should go back, do it several times to make sure gauge is not binding up inside the dash, it could just be a mechanical issue with the needle, not an electrical issue.

There should be 4 wires going into the tank,
2 for fuel pump 12v and ground
2 for sender 12v and ground

Fuel pump pair of wires would be a low ohm pair, under 5ohms using the 200 ohm setting, I would think
The sending unit pair of wires would be above 16 ohms(same scale) and ohms would change if you rocked the truck, as float goes up and down from sloshing fuel

 

[Eaglefixer]

going to change the whole unit out this weekend. I ordered the Spectra Premium SP37A1H from Amazon for $89.08. Also while i'm there got to change out the fuel filler hose.