HELP Fuel Pump Relay EKP/Engine Wiring Schematic

[George Hill]

OK... well here's how it works. The pump on US cars is PWM controlled by the EKPS, Euro cars have a plain jane relay ******(I imagine this is for emissions reasons, tougher standards over here)******, I just can't recall if the DME sends a PWM signal to the EKPS or not.

I can't decide if you are trolling or not... the EKPS and FP relay are both located inside the passenger compartment, they are nowhere near the fuel itself.

Continuing on as others reading may be interested, this is from the *****BMW MS S54 Training manual:******

"The fuel ....

BMW Tis says US relay is in the trunk and not passenger compartment. I'm interested to know more about PWM controlled fuel pump as you said. Could you provide the source of your information? Also, how does the DME control the European M3 mechanical pump relay with PWM, as I don't think a mechanical relay could respond to the 100 Hz PWM, and it would make a lot of clicking noise too? Unless the PWM pump speed control is only for US cars, then why such a wonderful feature was left out for EU cars?



Tis didn't say anything about PWM controlled fuel pump:

You literally posted a picture of the location for convertible which is behind the RR "door" panel, the coupe is located in the trunk. Are you even reading my posts?

The DME has two fuel pump outputs, one is PWM and goes to the EKPS on US cars (X60002 pin #11) the other is to ground the fuel pump relay coil on EU cars and all non-m us E46 cars (X60004 pin #10). ***Because of this you don't have to make any changes to the fuel pump system when doing a S54 swap into a Non-M E46 chassis.

[sapote]

I can't decide if you are trolling or not... the EKPS and FP relay are both located inside the passenger compartment, they are nowhere near the fuel itself.

Why do you think I was trolling? Who said that the relay was near the fuel or onside the tank? Fuel can leak and flamable vapor, and I was saying perhaps the US DOT required the relay to be semiconductor to avoid generating sparks. As about PWM or not, what I know from TIS is that it mentions nothing about PWM in the system description. I asked for your source of the PWM information as I don't have access to BMW MS S54 Training manual. If I called someone's wrong, or trolling, I will provide a readable or accessible source to prove it, not just saying or quoting it by myself.

You literally posted a picture of the location for convertible which is behind the RR "door" panel

Blame the TIS as it listed for the Coupe, see pic below:

OK... well here's how it works. The pump on US cars is PWM controlled by the EKPS, Euro cars have a plain jane relay ******(I imagine this is for emissions reasons, tougher standards over here)******,

I don't think the pump PWM control is for emission reasons, as the DME already uses PWM to control the injector injection duration which directly affects the combustion mixture. So I do think PWM control the pump speed -- if it is true -- is to save power: use less pumping energy for low fuel demand at low rpm or idle.

[George Hill]

Why do you think I was trolling? Who said that the relay was near the fuel or onside the tank? Fuel can leak and flamable vapor, and I was saying perhaps the US DOT required the relay to be semiconductor to avoid generating sparks. As about PWM or not, what I know from TIS is that it mentions nothing about PWM in the system description. I asked for your source of the PWM information as I don't have access to BMW MS S54 Training manual. If I called someone's wrong, or trolling, I will provide a readable or accessible source to prove it, not just saying or quoting it by myself.

Because whether the relay is in the trunk or cabin its no more exposed to fuel vapor than any other relay in those areas.

Blame the TIS as it listed for the Coupe, see pic below:

TIS is notoriously inconsistent unless you physically identify a car. When you manually select a car by its features (or even VIN) lots of time it is missing info or outright incorrect. The pic clearly shows its inside the cab because of the speaker and the white dot over the roof of the car in the lower left.

I don't think the pump PWM control is for emission reasons, as the DME already uses PWM to control the injector injection duration which directly affects the combustion mixture. So I do think PWM control the pump speed -- if it is true -- is to save power: use less pumping energy for low fuel demand at low rpm or idle.

My thought is that less fuel pump speed means less fuel is being moved. Less fuel being moved means less fuel temp and less vapor, less vapor that now has to be collected and dealt with (i.e. less emissions).

[sapote]

My thought is that less fuel pump speed means less fuel is being moved. Less fuel being moved means less fuel temp and less vapor, less vapor that now has to be collected and dealt with (i.e. less emissions).

Maybe, but I doubt the logic. I don't think there is any gas bubbles of fuel vapor in the pressurized fuel, as if there is, then the injectors cannot reliably meter the amount of injected fuel for a proper mixture. Especially at 72 psi it's not easy to have vapor.
The fuel delivery system is an sealed air tight system, and so even with more vapor formed in the tank, none of this is released into the atmosphere. Vapor due to the fuel being moved with engine running is nothing compare to when car parked under the hot sun.

I still am interested to see the source information of the PWM controlled fuel pump.

[George Hill]

Maybe, but I doubt the logic. I don't think there is any gas bubbles of fuel vapor in the pressurized fuel, as if there is, then the injectors cannot reliably meter the amount of injected fuel for a proper mixture. Especially at 72 psi it's not easy to have vapor.
The fuel delivery system is an sealed air tight system, and so even with more vapor formed in the tank, none of this is released into the atmosphere. Vapor due to the fuel being moved with engine running is nothing compare to when car parked under the hot sun.

I still am interested to see the source information of the PWM controlled fuel pump.

You are clearly not reading my posts, I posted my sources in post #31... I am done with this until Lou posts whether or not the EKPS fixed his car...

[sapote]

You are clearly not reading my posts, I posted my sources in post #31.....

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?

[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:

[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.

[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]

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).

[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]

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]

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?

[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

[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.