Gas gauge quit then works on interstate!!

[emerson1994]

The gas gauge on my 1994 Explorer XLT went to empty and stayed there for the last 18 months. On two occasions I filled the tank, drove on the interstate non-stop, and at the 150 mile point the gas gauge started to work. Very strange. I tried to reproduce strong suction by replacing the gas cap, no luck. I changed the fuel pump relay with a new ford unit. No luck. I realize it is probably the fuel pump and sender unit, but why would it just start working on the interstate...

Any ideas why the gas gauge would work after driving 150 miles non-stop? The gas gauge doesn't work in the city after 150 miles over a couple of days.

Thank you!

 

[FEAR30X]

track the ground connection wire, test wires 4 current,,

mine does the same thing
works when it wants to,

but i base my gas fill by miles driven give or take 20miles...

0 to 100-150 miles be4 refilling

 

[Roadrunner777]

(image removed due to potential copyright issue, if you need this circuit image, PM me, I'll find a way to get it to you) RR

Here is the circuit. Now, you can find the Y/W (yellow/white) lead from the fuel pump/sender and test it's resistance to ground, the spec it says is 145 for full, 22.4 for empty. You can pick up this lead at one of the connectors with 8 wires under the master cylinder. before it goes to the firewall connector.

But, here is what I find interesting: There's some gizmo called an anti-slosh module in the instrument cluster. I'm thinking driving highway for a long time means there is no slosh. Maybe this module is messed up in some way.

 

[Robert Nick]

The Anti-Slosh Unit provides Damping of Large Analog Voltage Changes from the Fuel Sending Unit. It provides a Stable Voltage for the Fuel Gauge when the vehicle begins cornering, braking, or hill descent. These type circuits are used by most auto mfgs. for stable fuel gauge performance. It is probably an Integrated Circuit such as an Integrator IC in the Cluster.

 

[Roadrunner777]

You could... turn the key on, don't start it... and leave it sit for an equivalent amount of drive time. See if the gauge works then.

 

[emerson1994]

Thank you very much for the wiring schematic. I will do the testing with my digital voltmeter.

The "key on" idea is interesting. Does anybody have input on that? The only thing I can think of that would be bad is battery drainage, which could be covered by a trickle charger.

Thanks again.

 

[emerson1994]

A quick follow-up with some internet research on the "anti-slosh module".

Quote:
First thing you need to do is check all the fuses and make sure you are getting power to the gauge. Then check the black/yellow wire at the fuel tank connector and make sure you have a good ground.

If power and ground are good, then ground the yellow/white wire at the fuel tank connector. If the fuel gauge goes all the way to FULL, you have a bad sending unit. If it stays at Empty, you have a bad gauge or an open in the yellow/white wire.

Ford has a special tester for the Anti-Slosh module. But if you replaced the fuel level sending unit and fuel gauge, and assuming the wiring is indeed good, then it's a pretty good bet the Anti-Slosh module is bad.

Second Quote:
The Fuel Gauge is connected to the Fuel Gauge Sender through the Anti-Slosh Module. The sender is a variable resistor connected to a float in the fuel tank which determines the amount of fuel in the tank Anti-Slosh Module. The Anti-Slosh Module provides a delay circuit to the Fuel Gauge which prevents the Fuel Gauge from fluctuating due to excessive movement in the fuel tank.

The Anti-Slosh Module is part of the instrument cluster and to replace it you will need to replace the entire instrument cluster.

 

[Roadrunner777]

A Google image search for 'Explorer Anti-Slosh Module' shows some representative ford modules (none explorer, but an F-150 and a Crown Vic). It is soldered on to the cluster flex circuit. It would not be difficult to replace if one had moderately good soldering skills. A great moment to replace all the bulbs and bypass the 20 ohm oil pressure resistor, I might add.

 

[emerson1994]

I successfully resoldered a $1000 motherboard for a pool controller, so I probably could handle the anti-slosh module, if that is the problem.

Thank you for finding that information.

 

[backfrmcolorado]

Not sure if my imput will help but....last spring i put a new fuel pump sending unit in. Everythinh worked great up until this past few months. Somehow the plug for the sendiing unit that connects to the truck shorted out causeing the guage to inproperly work. Just as you my guage didnt work, only difference is my guage was peaked out at full. I could drive 150-200 miles and it would be around 3/4 tank full. I went thru and straigt wired my fuel pump and sending uunit wires together and problem fixed. it might be worth a shot to try that as well.Idid mine with the little male and female conectors.

Good luck!!!
Adam

 

[emerson1994]

The ohm reading on the fuel sender wire at the firewall is a steady 17.4 ohms. Empty is supposed to be 22.4 ohms.

Because the gas gage worked a week ago on the highway that probably eliminates the anti-slosh unit. The anti-slosh unit allowed current to pass through it. Working on the highway also eliminates the gage itself as inop. With a steady 17.4 ohm reading my problem would be the sender in the tank, or a bad connection at the tank. I will put the Explorer on a lift and look at the connections.

Thank you all for your input. Hopefully this thread will help others with this common problem.

Bill

 

[bobbaloo38]

the fuel gauge in my 02 xlt has been on the fritz for quite a while. It happened when I was driving down a very steep driveway with potholes. It still works on rare occasions but as soon as I hit a speed bump it immediately zeros. I assumed it was the pump sending unit so I just have gotten into the habit of resetting the trip meter every fill up @ 250miles. Why did they put a trouble light for the fuel gauge unless they expected problems. Bob

 

[runningred92]

Mine stopped working completely for years and I would just fill up at appropriate mileage until I pushed it a little too far coming home late one night and ran out of gas on my street. I walked home and got a ride in the morning to get a few gallons to then go and fill up. And from then on it has worked. So maybe just keep a few gallons on till you run out of gas and see what happens. Not as technical or proven but if all else fails...