Every time I fill up, I watch my fuel gauge go from a bit past full to 7/8 in what feels like no time at all. I get that feeling like, ‘This thing drinks diesel!’ But then it seems to level out and go down normally.
Driving an ‘01 F450, usually towing around 20k lbs. Is this just me, or does anyone else’s gauge act like this? Wondering if it’s normal or if I need to replace something.
Could be the fuel level assembly in the tank. I had a truck that would stay full forever, then drop to empty really fast after half a tank. Replaced the assembly, and it worked fine after.
Tully said:
Could be the fuel level assembly in the tank. I had a truck that would stay full forever, then drop to empty really fast after half a tank. Replaced the assembly, and it worked fine after.
Interesting! My 6.0 has an issue too, where 1/4 tank means empty. But this 7.3 acts differently… it stays past full, then just jumps down to 7/8 and works normally. Someone else mentioned foam, but I’m not sure!
Tully said:
Could be the fuel level assembly in the tank. I had a truck that would stay full forever, then drop to empty really fast after half a tank. Replaced the assembly, and it worked fine after.
Could the 1/4 tank issue on your 6.0 be because the fuel pickup at the bottom is broken? Mine has the same issue—it can’t pull from the bottom of the tank, so 1/4 is really empty.
Tully said:
Could be the fuel level assembly in the tank. I had a truck that would stay full forever, then drop to empty really fast after half a tank. Replaced the assembly, and it worked fine after.
That actually makes a lot of sense. Guess I should check that out eventually too!
Hey, just don’t forget your fuel cap next time you fill up! 
Diesel is foamy! To get a true full tank, let the foam settle for a minute or two after the pump stops and top off again. Works every time.
Jem said:
Diesel is foamy! To get a true full tank, let the foam settle for a minute or two after the pump stops and top off again. Works every time.
Probably only gives you an extra 1/4 gallon if that, but yeah, every bit helps!
Might be a boost or exhaust manifold leak. When I got mine right, I hit 30psi boost, and the turbo spools perfectly around town.
Parker said:
Might be a boost or exhaust manifold leak. When I got mine right, I hit 30psi boost, and the turbo spools perfectly around town.
Nah, just rebuilt everything about 700 miles ago. The truck runs great—this is just something funny the fuel gauge does. Maybe a sensor issue? But no boost leaks, thankfully!
Got an ‘02 F350 with a big flatbed. My gauge usually doesn’t move for the first 200 miles after filling, but I just rely on mileage. When the low light comes on, I still have 3-5 gallons left. Guess these gauges all have their quirks.
@Harlem
Yeah, I’m not actually worried about fuel consumption. I get about 12-14 mpg with 4x4 and my gear ratios. Just thought it was funny, but maybe there’s a sensor or pickup tube issue in there too.
My ‘02 used to drop from a quarter tank straight to empty, so I had to keep it above half. Dropping the tank and replacing the fuel sensor solved it. These sensors get old after sitting in diesel for years.
My 6.0 sits at full for the first 140 miles, then drops steadily. These trucks can be unpredictable with fuel readings.
Jamie said:
My 6.0 sits at full for the first 140 miles, then drops steadily. These trucks can be unpredictable with fuel readings.
My 6.0’s pickup tube is broken, so 1/4 tank means empty. Found that out the hard way!
Last fill-up, I was under a quarter tank, but it only took 18 gallons out of a 38-gallon tank. I just go by my trip counter now.
Totally get it. Mine sits at full for a while, too, then drops. For what you’re hauling, that’s good mileage!
If it works, let it be. The fuel sensor’s likely just a bit off. My gauge acts up, too, but after 215k miles, I know what to expect. Ever notice this with any gas cars you’ve driven?
Phoenix said:
If it works, let it be. The fuel sensor’s likely just a bit off. My gauge acts up, too, but after 215k miles, I know what to expect. Ever notice this with any gas cars you’ve driven?
Can’t say I know… my dad got me started on diesels early. Bought my first truck, a ‘99 F350, with him when I was 16, and it’s been all diesels until now. Just got my first gas car last month, a 2016 BMW 320i that needs a turbo. Not looking forward to that repair, but I got it for a steal!