HELP Fuel Pump Relay EKP/Engine Wiring Schematic

[George Hill]

The closest i find is a M8X12 crankcase pulley bolt (07119900271), but not sure if the shank length is too long for the grounding terminal ring.

I think that one would be fine.

I pulled a bolt out of a clients car, but it looked long. It works properly and measured 14mm length measure from under the washer.

I then pulled one out of my car and it measured 12mm length from under the washer.

[y2k_o__o]

Its M8x1.25mm but I can't recall the length, short, something like 12mm IIRC.

I can pull one of out an engine in a bit and double check the length.

Thanks !
I tried with the heatshield bolt (M8 x 14), i couldn't turn all the way in with a few threads remaining, so yes it is definitely shorter (may be M8x10 or M8x12 ??)
did yours come with washer attached as well ?

can you also take a picture of it?
The closest i find is a M8X12 crankcase pulley bolt (07119900271), but not sure if the shank length is too long for the grounding terminal ring.

[George Hill]

Its M8x1.25mm but I can't recall the length, short, something like 12mm IIRC.

I can pull one of out an engine in a bit and double check the length.

[t3ddftw]

..

[y2k_o__o]

Sorry to bring this back

I lost that ground wire bolt, does anyone know the part number?

It seems to be a M8 bolt

[sapote]

As for the voltage being 0 with the relay disconnected, the DME was definitely not seeing a proper ground to send signal voltage

I don't think the DME needs to see any ground or signal from the EKP in order to send out pwm signal on its pin11. Here you can confirm this, measure at relay pin1 or DME pin11 whichever easy for you:
1) key turned on and during pump priming, I think the signal is 0V (active low signal would be 0v to run the pump)
2) after 20sec priming, DME turns off the pump by sending out the signal with 5v (or 12v whatever it is) to the EKP to turn off the pump. This inverted signal logic we called it Active Low logic.

Now, if what you will find out is opposite of what I just say, means active high logic, then the only way it works like this is the DME pin11 is an Open Collector with pull-up in the EKP circuit.

I thought all DMEs are the same for M or non-M but different firmware, so they should be not expensive to find on ebay.

[gheorghe]

I'm glad to hear that it was the bad EKP instead of a bad DME.

Me too, unfortunately in the panic of seeing the M3 sitting in the garage with a no start, I rushed and spent $950 for another DME off e-bay in case the EKP was not the cause. I'll be listing it for sale, hopefully I'll recoup my money.

As for the voltage being 0 with the relay disconnected, the DME was definitely not seeing a proper ground to send signal voltage, my DVOM as not providing a ground for it. I also do not think my DVOM is capable of measuring signal voltages coming out of the ECM, for that I would think a . I will try to answer my own question from a few posts back, to see what the voltage is to Pin 1 of the EKP with key in position 2 engine off and then with the engine running.

[George Hill]

So the root cause turned out to be a bad EKP.

Huge thanks to George for sending a replacement out and for the general help.
Also a huge thanks to LukeM3, sapote and Pnick for the diagrams and general help.

Moral of the story... miss the ground on the engine... mess up your EKP

Glad it worked out

[sapote]

Another way to explain why measured zero volt at DME pin11 while priming the pump: It is an active low PWM signal and not active high as I thought. Meaning with 0v (pwm= 100%) at DME pin11, the EKP drives the pump at full 100% 12v voltage, and 5v (pwm= 0%) at DME pin11 means EKP drives pump with zero volt. Can you confirm with at pin1 of the EKP connector?

[sapote]

I still cannot see how a loose ground of the coil pack driver circuit in the DME damaged the EKP module far away in the trunk. There is only one wire directly from the DME pin11 to the relay pin1, and it cannot explain why the EKP damaged but not the DME pin11 output driver.

[sapote]

I think this could be the reason why you measured connector pin1 with zero volt with relay disconnected: DME has an open Collector output transistor (not a relay as the Training document says) driving pin11 (or pin1 of relay connector) with the EKP having a pull up resistor to 5V or 12V inside the circuit board. So with the EKP removed, there was no pull up to 5v, and so you measure a normal working DME with pin11 open -- or floating voltage -- of the transistor in the OFF state (which is for driving the EKP to 100% 5V pulled up).

[sapote]

So the root cause turned out to be a bad EKP.

I'm glad to hear that it was the bad EKP instead of a bad DME.
But something is not clear here. You said:

I just measured the voltage with the relay disconnected and I see 0.01V at the EKP pin 1. When I hook the relay back and re-measure, I see 0.03-0.05V.

So with the bad EKP disconnected, then why DME pin11 connected to relay connector pin1 was only 0.01v when ignition key turned ON? It should be solid 5v or higher (PWM = 100% during priming).

[gheorghe]

So the root cause turned out to be a bad EKP.

Huge thanks to George for sending a replacement out and for the general help.
Also a huge thanks to LukeM3, sapote and Pnick for the diagrams and general help.

Moral of the story... miss the ground on the engine... mess up your EKP

[sapote]

Thanks for the copy. With the system drawings it helps me as I was confused about the text "The DME relay supplies voltage to the EKPS (M3- located in the trunk above the RR wheel well."
The text talking about EKPS and relay and I was thinking about the fuel pump mechanical relay (for Euro cars) plus the electronic relay EKPS for US cars. So the so-called relay is inside the DME (I don't know why the manual not just says the DME drives or controls the EKPS module instead of saying the relay drives the module. In fact I don't think there is a relay inside the DME to drive the EKPS as relay is too slow to drive a 100 Hz signal).
So we don't know the real reason of why driving the pump with PWM to control its speed, but this helps to explain why the US cars use electronic relay EKPS instead of the normal mechanical relay as Euro cars because mechanical relay cannot be PWM modulated to reduce its output voltage.

[t3ddftw]

George, I had read your post and I had said that I didn't have access to the training document. Just want to see the full section or pages where it describes the fuel pump PWM feature. Can you post the copy of the pages?

He did post them as attachments. Have a look: