1991 Ford Explorer 6 cyl Four Wheel Drive Automatic 212, 00 miles
I've owned and immaculately maintained this truck since 1992. Replaced just about everything except the drive tran and fuel pump. She's a great ol' gal and my OBX beach vehicle and I plan on keeping her in the sand for another 16 years GW. The fuel gage stopped working. Didn't float around, just stayed on empty. Tank was full. I dropped the tank & changed out the pump/sending unit. It didn't fix the problem. The gage was now registering fuel, just not the correct amt. I got a new pump/sending unit & repeated this process. This time I ohm bench tested the NAPA OEM Carter pump unit and it was perfect (16 w/float down, 160 w/float up) Reinstalled. Still doesn't work properly. Again, the gas registers, but I filled it and did not get above 1/2 tank. Today it registers 3/4. I checked the ohms at the connector. Should be close to 160, but it read 2.4 ohms @ 200. The first replacement unit registered 4.1 ohms w/float down. Is something shorting out the sending units, or could it be I damaged the sending units knocking the retaining ring back on top of the tank? I was pretty gentle. Pumps have worked fine, even the original was not acting up. Thanks!
Here's what I found for you Joe.
INSTRUMENT PANEL -1991 Ford Explorer
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Calibration Test (Aerostar, Explorer & Ranger)
1. Use Rotunda Gauge Tester (021-00055) to check fuel gauge. Place ignition switch in OFF position. Install rotunda gauge tester in circuit. Set tester to 22-ohm position. Turn ignition on. Wait 60 seconds, and then read fuel gauge. 2. If gauge reads " E", go to step 5). If gauge does not read " E", turn ignition switch off, then turn it back on. Tap on instrument panel and wait one minute. If gauge goes to " E", check for intermittent B+ connection at cluster connector, or damaged printed circuit. 3. Repair as necessary and repeat test. If after repeating test, gauge does not read " E", turn ignition off. Remove instrument cluster and inspect printed circuit for damage. Remove slosh module located on back of cluster. Connect jumper wire from gauge tester to fuel gauge terminal " S" (Yellow/White wire). 4. Turn ignition on and observe gauge. If gauge does not read " E", replace gauge. If gauge reads " E", replace slosh module. 5. Turn ignition off. Set rotunda gauge tester to 145-ohm setting. Turn ignition on, wait 60 seconds, and read fuel gauge. If gauge reads " F", check sender circuit wiring for shorts or opens with ohmmeter. If gauge does not read " F", turn ignition off and remove instrument cluster. See INSTRUMENT CLUSTER under REMOVAL & INSTALLATION. 6. Inspect printed circuit to ensure loop connecting fuel sender input to fuel gauge is cut. If loop is not cut, correctly cut printed circuit at loop. Remove slosh module from rear of cluster, and connect jumper wire from gauge tester to fuel gauge terminal " S" (Yellow/White wire). Reconnect cluster connector and recheck gauge. 7. If fuel gauge reads " F", replace slosh module. If gauge does not read " F", replace gauge. Check fuel gauge resistance using ohmmeter. Gauge should read EMPTY at 22.5 ohms and FULL at 145 ohms. See appropriate chassis wiring diagram in WIRING DIAGRAMS.
if the tank sender is OK it's probably the slosh module behind the cluster.