Petrol Fuel Pump Controller Diagnosis
 

Had another thread where I was concerned I had a fuel filter issue, with the fuel pump being replaced 2.5 years ago, due to intermittent no start issues. Turns out, as I'm sure many of you already know, fuel pump issues are common issue with this model.

Fast forward, I just replaced the fuel pump on my wife's e70 maybe a month ago and she just experienced another no start issue. Tried 3 times to start but to no avail. The 4th attempt it finally started.

This happened with 1/4 tank. I thought maybe then it was the siphon jet in the fuel tank that maybe failed. I gathered fuel system data via the hidden OBC menu before fill up and after. All numbers look good:


Hidden menu 06.00
1/4 tank:

Tank L R S Stats = 2.6 20.6 23
Tank Ohm- L R = 893.6 391.6

Full tank:


Tank L R S Stats = 41.9 37.5 79
Tank Ohm- L R = 085.1 100.9


I had already replaced the fuel pump relay in the earlier thread.

I believe what I am left with is diagnosing the fuel pump ECU.

Has anyone gathered data/tested the fuel pump ECU using ISTA/D or INPA and can share your steps/experience?

I can't seem to locate any mention of diagnosing the petrol fuel pump ECU on xoutpost. Only discussion I can find is diesel models.

I searched and was able to locate this page that walks through testing but they aren't using ISTA/D or INPA. I checked every controller in ISTA/D last night and couldn't find any place to obtain info on the fuel pump controller.

If you have a fuel pump relay you don't have a fuel pump controller (EKP).
There should be a wiring schematic on the relay.
1) Remove relay. With ignition on, confirm you have 12v at relay pin 30 in socket.
2) Remove relay and insert a fused jumper wire between relay socket pins 30 and 87. Fuel pump should run.
3) With jumper in place and fuel pump running, try to start engine.
4) If fuel pump doesn't run with fused jumper in place, you have a wiring, power or fuel pump problem.
5) If engine doesn't start with FP running check pressure at rail. If pressure is OK, you have something other than a fuel issue.

This may not be a fuel problem. If DME doesn't sense cranking RPM, it won't energize the fuel pump relay and FP won't run.

https://uploads.bmw2002faq.com/month...a59afa0757.jpg

Which is why a bad crank position sensor or misinstalled sensor prevents starting?

pshovest/ard, good points. Odd thing is no codes to point me anywhere.


I do have to say though, that when I go in to check codes there are certain random modules that appear to have issues(red) and I have to reset them(green) using ISTA/D.


Both alternator and battery have been replaced over the past 6 months. I mention that as I would attribute freak incidents like this to fluctuating or low voltage.


Would a similar K-CAN issue cause this type of thing? No codes, no dash lights either.

I was using your instructions to diagnose my car. I confirmed pin 30 and 87 has ~11.9V constant. However, when I bridge 30 and 87 the voltage drops to 0V. When I remove the bridge, the voltage between 30 and 87 goes back to ~12V on the multimeter.

Do you have any suggestions on why this is?

What are you using for ground on your measurements??

Thanks for the quick reply. What I did was:

1. Check the voltage in the coil pins (85,86). I did this by setting multimeter to 20V DC, sticking one multimeter probe (red/black etc) inside where the 85 male would go, and the other where the 86 would go. I got ~11.9V for this.

2. I checked the voltage in pins 30 and 2x87 similarly as above. I did not that one of the 87 pins (middle one of relay) did not have a metal connection in the female socket that the male relay attaches to. I got ~11.9V on the 30 to 87 pin with metal connections, 0V for the 87 pin with no connection (makes sense I think).

3. Next, after confirming the female sockets have correct voltage, I tried "jumping" or making a direct connection from the 30 to 87 pin (the 87 pin with metal connection). Nothing happened. I tried sticking the wire in a couple times to make sure it was in.

So what I did was plug in the multimeter probes to pins 30 and 87 with the multimeter setting at 20V DC again. I got ~11.9V. So what I did was, instead of unplugging the multimeter and plugging the jumper wires back in, I made a parallel connection with the jumper to the multimeter. I did this by touching the jumper wire to the multimeter probes. When I did this, the multimeter read 0V. Could this be because the current took the path of the jumper wire instead of the multimeter?

Yes, you are measuring voltage drop instead of voltage potential. Connect the negative test lead to ground for measurements. Sounds like your problem is not at the relay though, likely the fuel pump or wiring to it which you need to check next. Try to find some videos on using a multimeter.

Looking at RealOEM, there seems to be two fuel pumps in the 2nd row of the car: https://www.realoem.com/bmw/enUS/sho...diagId=16_0659.

Should I replace them in pairs if I find one to be not working?

No, there is only one pump.