Aftermarket fuel pump issues?

[PJmak]

Im not sure if this is in the right area since its not 500e related(well it could be since Im sure 500e uses the same or very similar fuel pump as my c43).


So Im chasing an issue on my car for a long time.

Symptoms:

-poor cold start(every time)
-poor performance(feels like its missing a third of its power)
-I had a missfire light twice before.

Parts replaced:

-Fuel pump
-fuel filter
-sparkplugs
-fuel sending unit
-cleaned injectors and refreshed orings
-tested injectors for pressure and they all hold(suspected stuck open injector)
-MAF(BOSHC) and tested MAF from my 05 C55 also. no change.
-all new vacuum lines
-new manifold gaskets


My question is: The fuel pump that I got when I first got this car was pretty cheap. Its for a c43 but it wasnt oem, it was some cheap brand. I mostly went this route because this car wouldnt start when I got it due to it sitting for five years. I knew most fuel related things would need rpelacing so I started by draining the fuel and replaing the pump and filter just to get the car started so I could move it around. I thought that pump would be ok but now im not so sure.

Im wondering if a cheaper, non OEM pump could be the coulprit? Maybe its not supplying enough fuel? Im out of ideas here and not sure what else it could be. Im gonna test the injector wiring harness but that rarely fails onthese cars. I also need to test fuel pressure but I dont have the guage yet.

I mostly wanna know if its even possible that the fuel pump could not be strong enough?

 

[gsxr]

If you can connect a fuel pressure gauge that is visible while driving, that would answer the question... rail pressure needs to be within spec at all times, including WOT. If pressure drops below min spec, the pump is likely at fault.

I think Pierburg is the OEM for that pump, they are not particularly expensive...

 

[195910]

Random cylinder misfires or specific?

As GSXR said, it could still be the fuel pump. you could still see the correct pressure on the gauge, but inadequate Fuel volume.
The later is a common issue on newer AMGs

 

[PJmak]

Hmmm Ill go and get a guage this weekend.....its good to have but ultimatelt Ill have to test with a different pump.