Lossing too much fuel need help

[99BoostedRS]

So i installed a walbro 255lph hp pump into my n/a 96 eclipse (rest of the fuel system is stock) because at the time i couldn’t afford a fuel pump and i had that one from my old car.

Ok so my problem is im getting really bad gas mileage about 150-200 miles a tank!

When i drive like a grandma (like really slow) i get pretty good gas mileage but once i start to put my foot to the throttle i use ALOT of gas. For example i had 3/4 of a tank and i floored it for about 3-4 blocks and the gauge just shot down to almost 1/2 tank?!?!?

I looked for fuel leaks but did not find leaks anywhere (and yes i looked by the fuel pump hanger followed the lines under the car and nothing)

Im not getting any check engine lights either

Does anybody know what can be going on?

 

[dsm racer91]

yeah i got the same problem and i dont know why

 

[Dankid69]

You might be burning too much gas cause your car is running rich. Check your exhaust area/tip to see if it is covered in black residue which is a typical sign of your car running to rich in fuel.

There can be tons of reasons why a car can start to get horrible gas mileage. Try the easy less expensive fixes first like doing your own tune-up to see if that helps. Bad 02 sensors can also cause you to get horrible gas mileage but at 80 bucks a pop you don't want to change them unless you definitely know that you need to.