Fuel Gauge Error?

[richkadams]

I recently filled up my 2014 FFH for the first time. The fuel gauge said the tank was 3/4 empty, but when I filled up, the tank only took 7 gallons. So, to me the math didn't add up. The FFH is suppose to have a 14 gallon tank. So, with 3/4 tank empty, the tank should have taken 10.5 gallons. So, I made an appointment to the local Ford Dealership and they told me that there is a 2 gallon reservice so people don't run out of gas. He said, "so basically, the car only thinks there is a 12 gallons tank.". Still the math doesn't work. At 1/2 empty, the car should take 6 gallons, at 3/4 empty the car should take 9 gallons. The service guy said he would send a email to corportate engineers to see what they say. Doesn't anybody else have this issue? To me, it sounded like a load of bull.

[corncobs]

No matter which car I have driven I never trusted the actual gauge.

Yes you think being electronic it should be correct but it might not take into account the reserve volume.

Miles driven and gallons used that's my measurement the fuel gauge display is anything but linear.

Edited December 14, 2013 by corncobs

[hermans]

13.5 gallon tank.

[jeff_h]

13.5 gallon tank.

 

...and the gauge will get more accurate after a few tanks once the driving habits are learned. Mine did the very same thing on the first tank, and the DTE was really conservative too, as there was no past history from which to base the numbers and thus it erred to the side of caution. So give it a few tanks and it should become more accurate.

[richkadams]

I just don't understand the "and the gauge will get more accurate after a few tanks once the driving habits are learned." Isn't this just a float or electronic sensor in the tank that is suppose to tell the driver how much fuel is remaining? The float or sensor is suppose to sense the amount of fuel remaining and report it. It shouldn't matter if I'm driving across country or to the store, when the gas gets lower, the sensor or float senses that and reports the gas in the tank.. No?

And even if the tank is 13.5 (my manual says 14.0), the math still doesn't add up. if my fuel gauge is reporting 3/4 tank used, the tank should have taken 10.125 gallons. If the mythical 2 gallon reserve is not counted in the car's logic, then

13.5 gallon tank -2 gallon reserve = 11.5 gallons the car thinks its tank is holding. 3/4 tank empty *11.5 gallon tank =8.625 needed to fill a 3/4 empty tank. Mine only took 7 gallons to fill. Something is amiss.

[acdii]

The fuel gauge is computer driven, it is not a true level reading from the tank, but a calculated level based on the past few tanks, computed MPG and an average off the level sensor in the tank. I have a theory on this that the calculated tank level and actual real levels are way off, and the only way to correct it is to drain the tank a few times so that each fill is closer to the actual 13.5 gallon mark, and then it will be more accurate.

 

That makes me wonder, if a hard reset is done that wipes everything clean on a full to the top tank, will it be more accurate than when it was booted at the factory with only a few gallons in it?

[B25Nut]

Rich - To get the maximum amount of gas in you have to go through three fuel shut-off clicks and hold the nozzle at just the right angle. You have to play around with it a few times. There is an extensive discussion on this issue elsewhere in this forum.

[richkadams]

@acdii - The service rep told me that it was a float in the tank.

@B25Nut - I filled the tank as much as she would take. The fuel gauge should completely full.

 

The car is in the shop now. Supposedly they are 'working with Ford Engineers' to figure out what's wrong. 536 miles on the car, 1 full day in the shop. They're keeping it over night.. My fears of buying a Ford seem to be coming true. :-(

[acdii]

There is a float in the tank, its position is relative to the amount in the tank, however, the computer determines how much fuel is used, and bases your fuel tank amount off that and not the position of the fuel float. Because fuel floats are not linear, and the level changes as you drive up and down hills and around curves, it uses the computer to determine how much fuel is in the tank based off miles driven and AVG MPG.

 

There is a great thread here with links to PDF from Ford with a lot of techichal information. I found on page 47 some details into the Fuel Level Indicater

 

"Fuel consumed" is continuously calculated based on

PCM fuel pulsewidth summation as a percent of fuel tank capacity. (Fuel consumed and fuel gauge reading range

are both stored in KAM and reset after a refueling event or DTC storage.)

 

It ins't just related to the Hybrids, the gas models have the same issue, in fact there is a TSB for the gas models, but not for the Hybrids. Doesnt make any sense, but thats what I found out when I brought it to my dealers attention.