Fuel gauge slow to change after fill up

[nbarr7655]

Hello all. My younger brother just purchased a 2000 Lincoln LS and added a decent amount of gas for the first time and now has a small issue. (I hope it's small).

After adding about 12 gallons of gas (tank was almost empty) he started the car and the screen told him he had like 90 miles to empty. Furthermore, the gas gauge hardly moved if at all off of E. He started out anyway and everything is running fine. While driving he watched the gas gauge slowly come up as well as the numbers until empty. By the time he got off the phone with me the gauge was at 3/4 tank and the mileage to E was over 200 and rising.

Ideas on what may be causing this and if it is an easy fix?

2000 Lincoln LS
114k miles
V8

 

[TrowaBarton]

No help as to the cause, but I know my 2000 was doing the same thing. Just try not to let it get so low and it will register the gas right away as long as you are filling with closer to a quarter tank rather than kcloser to empty.

 

[joegr]

It will do that if the key is turned to run while the tank is being filled. Otherwise, one of the two fuel level senders could be bad.

 

[StaySideways]

It will do that if the key is turned to run while the tank is being filled. Otherwise, one of the two fuel level senders could be bad.

Any idea why that happens? I noticed that a couple times and just wondered what caused it.

 

[joegr]

Any idea why that happens? I noticed that a couple times and just wondered what caused it.

Yes, it's on purpose. It's the way the anti-slosh routine is programmed. Without it or something like it, the fuel gauge would swing around as the gasoline sloshes around due to the car turning, accelerated, going up/down hills, and so on. The software knows that the fuel level should never go up while the engine is running, and it knows that it should only go down by as much as the engine is burning (it knows within a few percent how much is being consumed, since it knows the fuel pressure and how long it is holding the injectors open). This is not just an LS thing. Many cars are programmed this way.

 

[StaySideways]

Yes, it's on purpose. It's the way the anti-slosh routine is programmed. Without it or something like it, the fuel gauge would swing around as the gasoline sloshes around due to the car turning, accelerated, going up/down hills, and so on. The software knows that the fuel level should never go up while the engine is running, and it knows that it should only go down by as much as the engine is burning (it knows within a few percent how much is being consumed, since it knows the fuel pressure and how long it is holding the injectors open). This is not just an LS thing. Many cars are programmed this way.

Never really thought about gas sloshing around like that, good point, thanks for the info!