when you turn the key but not start it you hear the fuel pump turn on and then usually it thuds and shuts off.

problem here is it not shutting off its constantly on! and wont shut off causeing the car to go into limp mode! could it be the fuel filter causing this?

 

im also only getting like 15 mpg

 

I dont think its your filter. i would check your fuel pressure regulator.

 

already changed that!!!! not the problem must be something electrical!

 

what kind of car is it. it could be a problem inside the main relay. i had the oppisite problem with mine. but i just put my pump on a switch so that it does run constantly lol.

 

haha no its not the main relay i got another one and replaced it already! its 93 honda civic with the b16 swap

 

sounds like relay or you have a short. check all the wiring to the fuel pump