Car will not start, not getting power to fuel pump

[NaM3]

I have been having a problem with starting my car and after running the codes, I get fuel pump relay code. I replaced the relay located in the trunk with a brand new relay purchased from the dealer but no dice. My next step was to use a test pen to see if there is any power going to the fuel pump (larger red/white wire) and I got no power going to it. Also checked the fuse in the glove box and that fuse is good. Opened the fuel pump up and everything looked normal and still have half a tank of gas. What else can cause the no power to the fuel pump? I have heard the crank position sensor, is that true? If so, how do I check that?

Does anyone have the wiring diagram, particular to the area where the relay is? Under the relay there are two red/white wires and one red/blue. The red/blue I get power to but the red/white I can only get one wire on when I turn on the ignition however no power going to the other red/white wire which I believe is the one that is being sent to the fuel pump.

[NaM3]

Nevermind, I got it to start and all I had to do is to clear the faults on the DME using INPA.

[dukeofchen]

Is the fuel pump relay in the trunk? I'm troubleshooting a potential fuel pump issue myself right now, and at least on non-Ms it seems that the relay is in the panel behind the glove box.

[ATB88]

On the coupe it's in the trunk. Convertible it's behind the rear passenger side arm rest.

[NaM3]

Fuel pump relay is in the trunk for coupe right on top of the rear tower that house the shocks.

[NaM3]

I got the car running for a few days and drove it a good couple hundred miles but now the problem came back. I have both my new and my old fuel pump relay and I am getting no power to the fuel pump again. Ran INPA and got error code 1 for fuel pump relay. What else can cause the fuel pump relay not to turn on the fuel pump? I have heard crank position sensor, is there any truth to that?

A thought: can it be the EWS system cutting the fuel? If so, how can I test that?

[eacmen]

This is not specific to our cars but a good thread on diagnosing potential fueling issues.

https://www.bimmerforums.com/forum/showthread.php?2200546-Help-last-try-on-the-fourms-Fuel-pump-relay-will-not-activate

[NaM3]

Thanks for the link eacmen! That gave me a lot of ideas on where to look at.

So far I have BMW code 1 for fuel pump relay still even after purchasing a new relay from the dealer

- Checked fuse 54 in the glovebox and it is still good
- Replaced the fuel pump relay and still have the same problem - Then I learned that you can check the fuel pump relay using INPA telling it to turn on and it did. So the fuel pump relay is not the problem
- Checked the fuse in the engine bay next to the DME (fuse 3) fuse is good
- Jumped the wires to see if the fuel pump still works and I can hear the fuel pump starting up
- Using a test pen, I tested where the wires plugged into the fuel pump and I believe it was a red/white cable, I got no power to the fuel pump
- lastly, while cranking, I can see the rpm goes to around 100-150 - does that mean that the crankshaft position sensor is good? If this is not a sufficient way to test the CPS, I can take off the manifold to get to it but I don't want to get in there for nothing.

Side note, I started the car about a couple dozen times and it will fire up once every 10 times or more. That one time where it starts, it would die out after maybe 10 seconds.

Any ideas?

If it is EWS related, the will the car still crank?

[NaM3]

I just had the crankshaft position sensor tested

I was able to get 2.5 volts from both signal and ground
I then jumped the signal to the ground with my multimeter and was able to get a .8 volt reading while cranking. The pelican article said I should be getting .5 volts but I dont think that really matters as long as I get some voltage output
So I believe the crankshaft sensor is working properly

At this point, I am running out of ideas. The funny thing is, every once in a while it would start up for a few seconds then slowly dies. I was able to use the test pen to check the red/white wire on the fuel pump relay while it was running and it does show that I am getting power to the fuel pump but then dies along with the car.

This is the article on how I tested my crankshaft sensor

https://www.pelicanparts.com/techart...20engine%20RPM.

[Arith2]

Here's a description of how the EWS works. If it is somehow EWS, which may be possible, then that's going to be hard to diagnose. You could et Martin's tool and delete it for like $25-30. That would eliminate if it's EWS or not for fairly cheap.

[NaM3]

Here's a description of how the EWS works. If it is somehow EWS, which may be possible, then that's going to be hard to diagnose. You could et Martin's tool and delete it for like $25-30. That would eliminate if it's EWS or not for fairly cheap.

Thanks for the info, I happen to already have Martyn's tool and I have disabled the EWS but it made no changes. So I guess I can rule out the EWS.

As its current state, my car usually does not start but it would start maybe once every so many attempts or if I leave it then come back to to try to start it again. It would start then idle would jump for a few seconds and die out.

While the car is running, I get signal from the relay to the pump (again red/white wire). When it dies, the power from that wire is gone too. I am using a test pen to see when that wire would go on and off.

Is this another bad relay or is it something from the DME that tells my fuel pump to shut off? Could it be my crankshaft sensor? I usually get .8 volts front the sensor when cranking but it would jump from .1 to sometimes over 1 volt AC.

Are there any other components that would make the DME tell the fuel pump to not start?

[Arith2]

The problem with these intermittent issues is they have to be recreated and tested exactly when the problem occurs. Once it occurs you have to save the data and review. If the signal from the CKP is dropping out and the DME is killing the engine, I would think that it would throw a code for a CKP. To properly diagnose a crank sensor, you'll need an oscilloscope. Those are way out of your price range and you would save money just swapping the engine over buying one. I would test across the fuse box crossing terminals 86 to 85 on the relay while the vehicle is on, and then the same from 87 to 30. 87a could also have a function on it but I'm not sure. It's unlikely the relay is causing this but you also test resistance of these wires. Check voltage drops across wiring from one connector to the next. When that's functional use the half step method to isolate the problem circuit. Start half way and measure the second half(or first half is you want), then switch to the other half. The one that shows a problem, you now do the same thing until you can isolate it. There are only so many halves. Just make sure when you're check these, you aren't piercing the wire insulation because that's how you get shorts to ground everywhere.

[Dash1]

Your fuel pump could have gone out if everything else checks good

[Arith2]

Could buy an amp clamp and check amperage.

[NaM3]

Thank you everyone! I finally got to the bottom of this. After checking the wires, it turned out I had a bad ground to the fuel pump.