This one has me baffled. 3 weeks ago, we're filling up to drive about 80 miles from Melbourne to Orlando for a vacation. The tank is less than 1/4 full. I add a bottle of Chevron fuel treatment/injector cleaner and fill the tank. I've never used the Chevron before and actually rarely use any additive. The truck was off while fueling and it was our normal gas station. We drive away and the gauge still reads less than 1/4 full so we pull back in the parking lot. Cycle the key a few times, no help. I say "let's go, we know it's full". It slowly moves up to a true reading by the time we finish the 90 minute trip, about 3/4 tank at destination. The wife fills the tank last week and says it does the same thing. She drives 15-20 minutes twice per day for kids school. She said it took multiple trips for the gauge to read true. So it seems to be based on how long the truck is running, not how much time goes by. Anyone have any thoughts?

 

Sounds like the cluster is stuck in "slosh mode" which takes 55 minutes of accumulated driving to move from E to F.

I know that there's a TSB (06-2-12) for the Explorer of this vintage for this issue, but I don't know if any of it is applicable to the Expy/Navi. I'd suspect the basic info would apply regarding how the cluster works. You might want to review that TSB to see if anything applies.

 

I had this same thing happen with my 01 navigator I bought a few years back. For the first couple of fill-ups the gauge would start a 1/4 then ever so slowly it would creep up. After those couple of fill-ups it never happened again, so you might want to fill it a few more times and wait to see if it clears up on it's own. The only other thing I did in the interim was disconnect the battery to work on an electrical circuit, so you could disconnect the battery for a bit and see if that forces a recalibration.

 

So I searched about this "slosh mode" and found there's 4 different modes the gauge has.

1. Anti-slosh (default) - 55 minute guage response
2. Key OFF fueling - 2 second guage response, if conditions are met
3. Key ON fueling - 90 second guage response, if conditions are met
4. Recovery - 20 minute guage response, if conditions are met

I figured checking the Key ON fueling would be an easy test...filled up last night with it running and bingo, by the time I got back in the seat the gauge read Full. One of the conditions for Key OFF fueling is an ohm reading of the fuel sending unit. So I figure it's an issue with the sending unit since the guage switched modes. Guess I'll live with it for now.