E90 - Problem with fuel pump

[maxhouse18]

I'm having some issues on my 2008 328i.
Car at times it does not want to start, it cranks for ever and ever.
However, when it starts, it runs perfectly, and after that point restart perfectly.
So, some days it just does not want to start at all, other days it starts perfectly, nothing in between.

When it does not start, I determined that the fuel pump does not run at all. I think It is a problem in the voltage supply, perhaps the relay?
I measure different voltage level at the pump, sometimes 7V, sometimes 9V, other 12V. Not sure, but it seems that when it is >9V it runs fine (which would makes sense to me).


I'm looking for the location for the fuel pump relay, I cannot find it.
Is it suppose to be on the back of the glove box with the other fuses?

Please help with locating the relay or any other tip related on my problem.

Appreciated
Have a nice day
M

[mryakan]

Silly question, but did you check the battery 1st?

[fun2drive]

Suggest you get a Bentley manual and that will spell out where all the electrical relays and fuzes are located.
FYI BMW typically uses a negative pulse signal to close the circuit on the fuel pump relay and there are times when pressure and volume are adequate the pump will not run at all. This would be turning the key to pos 2 and allowing the pump to pressurize the fuel rail. It will maintain pressure until you engage the start feature and the pressure and volume demands turn it back on.
Hope this helps some.
Does sound like a possible fuel pump relay issue...

[d318spence]

I am having what sounds like the same issue on my 2006 330i. Wouldn't start in the garage two weekends ago. Mechanic had me try to start it with the gas pedal fully depressed and it started right up. Took it to him and he recommended a spark plug change as I was at 72,000 miles. Ran fine for a few days and then started running really rough on a business trip this Monday. Stopped and turned it off for about 10 minutes. Ran great until today when I stopped for gas. Went to start and wouldn't start, even with the gas pedal fully depressed. Waited about 15 minutes and it started right up with the pedal fully depressed. Ran great the rest of the day. I have not seen any error codes at all displayed.

I am 600 plus miles from home. Is this something this can go out completely and leave me stranded (my guess is yes) or is it more just a pain?

Thanks.

[maxhouse18]

Silly question, but did you check the battery 1st?

Good question. After the problem appeared first, I went to a local mechanic, explain the problem (at the point the car was running fine agin).
They convinced me to change the battery (!). So I have a new battery but the problem is still there.

So, it happened twice in the last 2 weeks. Car would not start, put my hand on the connector, pressed it down, and the pump + car would start and work fine after that.

I'm very confused now, it could be the connector not doing good contact (!). All of this seems a bit weird to me.


Suggest you get a Bentley manual and that will spell out where all the electrical relays and fuzes are located.
FYI BMW typically uses a negative pulse signal to close the circuit on the fuel pump relay and there are times when pressure and volume are adequate the pump will not run at all. This would be turning the key to pos 2 and allowing the pump to pressurize the fuel rail. It will maintain pressure until you engage the start feature and the pressure and volume demands turn it back on.
Hope this helps some.
Does sound like a possible fuel pump relay issue...
Thanks, for you answer it helps.
I'm trying to get my hands on the Bentley manual.
Good to know about the negative pulse. Not sure what pos 2 is for my car, I have the push button to start the car. I measure the voltage when I push the start (when the car start cranking). I would expect at that point the pump to run in full it is the time when the pressure is needed I guess, especially after the car has been sitting there turn off for while.

[Rev JJ]

I have the same question for a 2008 328i E90 with the N51 engine SULE, Skimming posts here I see answers all over the place.
My wifes car, bought at a fair price according to Carfax (Now I know why) started misfires - ran so rough it could not go up a hill. So I borrowed a generic odb2 meter:
Misfire on 1
Misfire on 5
Random misfires
SO I pull the plugs - the are crap - all need to be replaced - Did so -
Car started but still ran rough - replaced the igniters? - sorry dont know the terms yet
Checked with the odb2 tool - and my dash went into EMP Pulse mode like you see in the movies and there was a loud POP.
Oh and the windshield wipers came on, nice touch...
Well Battery was draining fast I could watch the voltage go down.
SO I slapped a charger on it, did a slow charge overnight -
Car would crank but (At that time I did not know to press the button a 2nd time to stop it) but in a short amount of time <1minute time to charge again
SO I slapped a charger on it, did a slow charge overnight -
Stared to do an old school test - No errors on the ODB2 - so that must mean the plugs are firing - I have ordered the ignition testing kit another poster suggested - get it in a could of days.
Started looking at fuel - I have never seen a more cryptic fuse panel in my life - Luckily another poster here had translation key and I learned fuse 70 was for the fuel pump. It was good.
So next would be the Fuel Relay - I have seen posts that say engine compartment - passenger side, Passenger side fuse box, passenger side rear side panel above the tank...
Oh and I have the wonderful 1/2 tank works issue - will look into that after I get it running.
SO can I get a best guess, in the ball park, location for the fuel pump relay - or is it only a control module?

May the comedic errors of this newbie bring you joy and mirth!