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I own a 2004 f-150 5.4l I replaced the engine with a new 2013 and now ever so often I get a low fuel warning on display but fuel gauge shows over 1/4 tank does anyone know if I have to recalibrate the fuel system with new engine? I thought when main computer plugged back in after engine change it would reconfigure everything

rubbinsracin

So you replaced it with another 5.4 or you swapped in a 5.0 or 6.2? They no longer had 5.4 motors in the '13 model year. If you have a "newer" 5.4 I would guess it is your sending unit in the tank. Might try a computer relear by pulling you NEG (-) battery terminal off overnight and putting it back on. Could also be the gauge on the dash is faulty. Never seen it on an F150 but I guess its possible.

bonez

Haven't replaced my motor, but I have issues with my fuel gauge and low fuel warning alert too. I actually have a couple different issues, and I'm not sure if they're related or not. I'm guessing they are, but not positive.

The first one is similar to yours, where my fuel gauge reads a quarter tank or so, and my low fuel warning comes on. If I check my trip odometer, I know I still have more than 50 miles to go on the fuel left in the tank. Sometimes the "Miles to Empty" goes down somewhat normal and will eventually reset itself to the correct amount of fuel left. Other times, it will come on and say "50 miles to E" and it will drop a mile about every 100 feet I travel.

The other issue I have is every now and then when I fill it completely up, after restarting the truck, the fuel gauge will barely move above E when I just got done filling the tank up. I have to drive it a few times before the fuel gauge very slowly creeps all the way up to full.

I'm guessing there is some sort of sensor in the tank or fuel line that measures how much fuel is left in the tank and it's going bad. Not sure exactly what that is, but maybe it's the "sending unit" like rubbin said above.

jamie930

the "low fuel" comes on when it gets to "50 till empty" The miles to empty is based on the mpg and the amount of fuel it thinks it has. So if you have been driving in town and your mpg is down to 10 the low fuel light will come on around a 1/4 of a tank

Serapis

I think this is the correct answer.

bonez

Yes, this is how it works. Mine will randomly have a problem with the "thinking" part, because whatever is used to figure out how much fuel it "thinks it has" isn't reading the correct amount of fuel.

My driving is basically the same routine on every tank and I get about 10 mpg's. An example of the issue would be:

I get roughly 250 miles to a tank, and this would allow just a small amount of fuel to be remaining in the tank. My "50 miles to E" will come on sometimes after only driving 150-160 miles on the tank, and the 50 will drop rapidly. About 1 mpg every 1-2/10ths of a mile. At some point, sometimes after stopping and starting the truck again, the "xx miles to E" will go away and once I get to around 200 miles on the tank, it will come back on again. Other times it will just go away while I'm driving.

I believe the OP is referring to somewhat of a similar problem. Yes, mpg's will vary from tank to tank depending on your driving habits, but they shouldn't change in a fashion where the "50 miles to E" comes on regularly at 1/8 tank, and then just all of the sudden comes on with over 1/4 tank. I could see it happening if you regularly drive like a granny on flat land and then compare that to towing a 5,000 lb. trailer through the mountains.