500 se fuel related problem
 

I have a 1984 500se and since i got it, it always made a hissing noise by the fuel pump and then after 5 to 7 min it died i cranked it again it would turn right back on, so i changed the fuel pump and fuel accumulator fuel pump relay but now with the new fuel pump i turn the car on still makes the hissing noise and dies quicker after 1 to 3 min, if someone knows about this problem
I would really appreciate the advice.


Thanks