Hey all,

I just replaced the battery in my SO's 2010 MCS, after it died on the driveway yesterday.

Next problem: For the past view days, I've noticed that there's a slight whirring sound coming from around the driver's side rear wheel, and I'm guessing it's the fuel pump. But the engine is off, so I'm guessing that might be the cause of the dead battery... Any thoughts?

After replacing battery, the car started right up, runs smooth like it always has, but after I shut it off, that pump-like noise is still there.

Anyone have any idea what it is, and what I need to do about it?

Thanks in advance
JC

UPDATE: I just went and pulled the fuel pump relay. The sounds stopped, so that's what was running. Good... but the relay was very hot. Hopefully a new one will fix it.

 

Let us know what happens,yes it should not be running all the time.

 

Relay replaced, pump immediately started running again. Anyone have a suggestion what else could be the problem?

 

yes, something is not hooked up right, did you have any other work done, bet the battery died from the pump running, Other than maybe an internal short on the pump itself which you would have to replace it to find that out.

 

No, there was nothing else replaced and no other work done. And yes, the old battery died from the pump running. The car doesn't have IBS, so I understood it was ok just to swap out the battery.

The car has ran flawlessly for over 2 years since we bought it, but with no work having been the done, the pump just recently started this. Sounds like I'm replacing the pump.

Thanks!

 

before you buy a pump, you would want to identify actual fault. when pumps go bad, they stop working. with that in mind, there are two locations where a stray signal can keep the pump running. look at this diagram https://www.newtis.info/tisv2/a/en/r...upply/CkMjECaN. one case could be K96 contact is stuck closed and the other case case be the signal from the ECU is shorted (to positive). the other third case is a short to positive on the wire going to the pump.

with this information, you could try to isolate the ECU by removing the relay in the fuse box next to it. I think it is the 1st one, or just remove the first two. If the pump is still running, then you know the fault is after the ECU. meaning the ECU is not shorted and you could move to the next step WHILE the relays are removed.

Then, you move to the fuse box behind the passenger kick panel. find the blue/white wire and disconnect it. you could use a pick to open the tab and pull the wire out. if the pump is still running, then there is a fault AFTER the fuse box. if the pump stops, then the fault is in that built in relay K96.

you could further diagnose that K96 relay on the bench to see if it's stuck or not.

hope this gets you somewhere.

 

Very detailed information, very much appreciated.

Hard to focus on all the details while I'm here at work, but:

I already know the pump can be stopped by pulling the relay, so that rules out the ECU?

I really only have time to work on it at evenings and weekends, but I'll dig in and absorb all your info this evening.

 

if the pump stops working after pulling the ECU relay, then the fault could be from the ECU. in this case, I would locate the Violet/green wiring at the fuse box and disconnect it (with the ECU relay still installed). This is the fuel pump activation signal.

post here as you go though the trouble shooting. I might be awake to assist.

 

I've pulled what I understood to be the fuel.pump relay and the pump stopped. I haven't touched the ECU relay... or did I? I pulled the only relay visible in the fuse pane at the passenger side (right) kick panel.

 

https://www.realoem.com/bmw/enUS/sho...diagId=61_3743

the fuel pump relay is built in the fuse box. the one you removed must be the main relay.

 

OK, so... I bit the bullet and decided to have a diagnostic at a local electrical specialist. I'm very happy I did....

I was in the right ballpark looking at the relay, and all the suggestions about DME/ECU were potentially in play when I first talked to the guy. So I left it with him overnight, and went back this afternoon. He had figured out the problem, and wow..... No issue with the DME/ECU, or the fuel pump itself.

Apparently the car has been a victim of PO meddling. It never occurred to me that something like this would happen, but evidently someone in the car's history decided that they needed to splice in an additional relay into the same circuit. I have NO idea what it could possibly be for, but the guy at the shop checked it all out, then disconnected the "repair". My best guess is there was a fuel pump "problem", centered around the relay, but a PO went down a different path to effect a repair.

The pump now shuts off as it's supposed to, and the car is running just fine the way it always has. And I didn't have to spend hundreds/thousands to get it resolved. He charged me the flat fee for diagnostic, and not a penny extra for the fix.

Realistically there was no way anyone could guess what was wrong with the car without looking at it in person, but your input was crucial in helping identify the problem. Thank you MiniToBe!

 

Interesting find lol...glad it was spotted without throwing parts at it. Good works 👍

 

Interesting. The pump in my 2013 Cooper S was running after turning off the engine off today. It was a hot day and I assumed it was just running to cool the fuel in the system. It did shut off after a few minutes.

I’m the original owner and no mods have been performed. Not really concerned at this point.