My problems started last week when my R53 wouldn't start. Turned out to be the fuel pump. After replacing the pump it started right up and ran for a few minutes so I shut it down. I thought the level sender wasn't working correctly so i pulled the pump again and re-positioned it so the level sensor arm could move freely. Now the car wont start at all. I prime it a few times and it just spins like its not getting fuel again. I know this is a non-returning fuel system, could there be air in the fuel rail that needs to be bled by the schrader valve?

 

fill it to the brim with gas and see if it starts. you do not need to bleed the rail
seems like you dont have the pump in all the way

 

Well when I came back to it today, I primed it and to my surprise, it ran, for about 3 seconds. It then went right back to what it was doing before, turning over but not starting. I pulled the cover off the pump well and found it wasn't priming when the key was turned. It would just make an audible 'thud', no whining or whirring to tell me its working.

So I pulled the pump again and bench tested it. It was doing the same thing the broken pump did, just a 'thud' and no spinning. But, After putting power to it a third time it started working. I decided to put it back in the car and after priming it a few times the car started and drives beautifully.

I have no idea what happened or if/when it will do it again. It's actually rather unnerving driving around wondering if the pump's just gonna die.