Insane MPG in a cobra?? Help please!!

[Auto]

My fuel pump crapped out on me the other day, 01 cobra with 76k miles... I replaced it with a new Bosch fuel pump because I got it for more than $100 less than what Ford wanted. While I was down there, I also replaced the fuel filter and everything works normal again..

However, my fuel gauge seems to be off... it stays full for a while and then moves ever so slightly. It's accurate when the tank is full but I am thinking it is off by about a 1/4 tank. Where before I replaced the pump I was at 110 on the odometer at 1/2 way point, it now shows 160 miles on the odo. The other day I filled up with gas and it took 9 gallons when the needle was just above the 1/4 hash mark.. I have not tried to run it til the low fuel light just yet, maybe I should?

My fuel mileage is normal, avg'd 26 mpg all highway this weekend. Any thoughts on what the issue could be? It is a brand new whole unit assembly, out of box, could it be a short? Sending unit?


Cliffs: Just replaced fuel pump with a whole new assembly, fuel gauge appears to be off by almost 1/4 tank now. MPG is normal and car runs great. Have not yet tried to run it til the low fuel light comes on ... Any ideas why the gauge appears to be off?


Any thoughts would be appreciated. Thanks!

 

[99BlownVert]

I think it was wrong before and it sounds about right to me now, thats about how every mustang I have ever owned has worked.

 

[TBCobra]

My gauge stays at full for a little then moves ever so slightly after that.

 

[Wabish]

26 mpg?! I must have been doing something wrong...

 

[Brutal Metal]

maybe your fuel level sender got bent etc.. when the pump was changed and isn't perfectly sitting where it's supposed to?

 

[SonicBlueOval]

maybe your fuel level sender got bent etc.. when the pump was changed and isn't perfectly sitting where it's supposed to?

x2

 

[Butterybunz]

26mpg?!?

After 50 miles my needle starts moving down

 

[01yellercobra]

26mpg?!?

After 50 miles my needle starts moving down

These motors really like to be on the open road. The stop and go kills the mileage.

 

[Darkc0bra]

These motors really like to be on the open road. The stop and go kills the mileage.

This is true. With my 4.10's and an aggressive tune I get 24 on the highway going 80mph at 3k rpm. So 26 I can see happening with stock gears.

 

[mustangvsix]

yeah 26mpg on the highway is fine, I get at least 23-24 on the highway normally, and have hit 29.8mpg on a highway trip with a light tailwind and 80mph.
as for the gauge mine sits until 45-50 miles then falls to 1/4. From that point to E it seems to read better/more accurately and falls normalish, maybe a bit quick on the 1/4 to 1/2 but something both my mustangs have done.

 

[Butterybunz]

I guess I always do a couple 100+ mph pulls when I'm going on long trips so I only get 23.

 

[Auto]

ya, my 26 mpg was suprising to me too, but I'll take haha ... you guys think I should chance it and see how far I can go til the light comes on? I really don't wanna drop the tank again

 

[01yellercobra]

Throw a gas can in the trunk if you want to try that. That way you can make it to a gas station if need be. The very least you would know how far you can push it on your gauge.