Fuel gauge stuck at full after sending unit replacement/ cleaning tank connection
 

Hello everyone, new member here and I have a 1993 4.0 five speed regular cab shortbed that has a fuel gauge stuck past full I’m trying to fix as my speedo and odometer just quit..(internal driver gear in tcase needs replaced??) anyways I just put new sending unit in since the tank was out. Cleaned connections and added some dielectric grease. Both ground wires at fuel pump plug light up my test light when connecting to battery positive to see if they were grounded. I’m guessing a grounded wire or bad gauge but how to can I be sure? Also looking for information on fixing that speedo drive gear inside tcase. Thank I’m advance! Adding pics of gauges and gear damage
https://cimg2.ibsrv.net/gimg/www.ran...d634dc12e9.png
https://cimg3.ibsrv.net/gimg/www.ran...8169d726f.jpeg
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You will need to pull the tail shaft housing on the 2WD, no fluid will come out
And replace the Worm gear, should be 7 tooth

The 1993 sender in the tank uses these parameters
16 ohms = empty
160 ohms = full

OHMs are resistance, and in this case its resistance to ground

If sender wire is disconnected then that would be HIGH ohms because there is no connection at all, so would show as above FULL on the gauge, a direct connection to ground would be 0 ohms, so below EMPTY on gauge

Gauges rarely fail its 99.9% a wiring or sender issue

If you still have access to top of tank then use ohm meter to test sender, should be between 16-160 ohms depending on gas in the tank, and then rock the vehicle, OHMs should go up and down as the float/sender change positions

The Yellow/white wire is the wire that goes to the gauge, same color all the way to back of cluster, if you GROUND this wire then turn on the key gauge should go to below EMPTY, 0 ohms to ground

Thank you for the help!! sorry forgot to mention it is a 4x4, not sure if that would change much? I also have it back together currently. Am I able to check the reading at the yellow white stripe wire in the harness under cab area? Easy to get to. I cleaned everything before putting back together so if it’s a problem at the plug the wire is broken. I spliced that ground and added a second directly to chassis.

Sure test away
Key off
If you see between 16 and 160 ohms at the tank then wire from there to the gauge is most likely broken

so correct me if I’m wrong. if I see between that range at the wire I mentioned that means it’s all good? So my problem would be the gauge. If it’s high then wire is broke somewhere between the gauge and plug. It gradually falls some when it’s off or you cycle the key, but as soon as you turn the key it slowly rises back to 1/4 inch past full. Is that yellow/white wire just directly connected to the gauge harness plus basically? Haven’t pulled gages out yet, had trouble getting them to pull out enough. I’m not good with wiring issues haha. Thanks again!!
-Regis

Up thru 1994, Rangers have speedometer cables, so to get the dash/cluster out you need to pull it out as much as you can and then reach in to release the speedometer cable

Google: Ford ranger speedometer cable release video

There are a few videos and how-tos
Also speedometer cable comes in thru the firewall so look in engine bay to make sure nothing is preventing the cable from sliding in a bit so you can get at it from the inside


cluster(12v-----gauge)------------yellow/white wire-----------------------------------------------------------------gas tank sender----------------------------ground

You have 12v at the gauge because needle moves with key on or off, in 1993 it might still be a pulsed 5volts, doesn't matter, you have voltage at gauge because needle moves

So either yellow wire at back of gauge/cluster is unhooked or the yellow wire is not connected to sender

Test yellow wire when its unplugged from the cluster, should see 16 to 160 ohms with other meter probe grounded, rock the truck and ohms should go up and down as float goes up and down
If you don't see this then yellow wire is not connected to sender

If you plug in the wires on the cluster and turn on the key
gauge will go to FULL
Then GROUND that yellow wires connector and gauge should go BELOW Empty, that means gauge is working, 0 ohms is short to ground, under 16 ohms so below empty, high ohms, above 160 ohms is no connection so above full

1994 Cluster wiring below, 1993 will be the same
Yellow/white wire is on pin 5 connector "B"

Just as a heads up, Rangers have an "anti-slosh" module on the back of the cluster, this prevents the gas gauge needle from going up and down every time you go around a corner and gas sloshes around in the tank, hence "anti-shosh" module
When these fail the gauge usually reads EMPTY all the time not FULL, but anything is possible
By-pass for anti-slosh module here: https://www.therangerstation.com/for...o-work.140669/