HELP Fuel Pump Relay EKP/Engine Wiring Schematic

[sapote]

Thank you for the great info guys! I have it narrowed down to the EKP.

EKP Pinout results:
Pin 1: DME signal from X60002 PIN 11 - I have 0.5V with key ON
I know the pump works if I jump it and since I am not getting anything out of Pin2 I am lead to believe the EKP is bad.

Pin 1 should be 5v (or 12v I'm not sure) to turn on the relay during pump priming or running. If engine not running then pin1 is logic high (5v or whatever higher) only a short time priming. So something is wrong: either the DME pin11 output is bad (zapped by ignition high voltage event) or the wire from DME pin11 to relay pin1 is opened or shorted to other conductor.

1) try to check continuity from relay p1 to dme p11 with long test wires, or
2) disconnect the wire at DME pin11, then measure pin11 when key turned on; should be 5v or higher, momentary, if not, looking for another DME or repair it.

[gheorghe]

Looks like I might have been a bit too excited. I just measured for voltage right at the X60002 connector pin 11 and I get 0V with the key on. Looks like I need to look for a place to repair my DME or a new DME

[George Hill]

I've seen the coil ground loose in the past and it cause the EKPS to fail. Car was in the shop for a valve adjustment, came back on the tow truck with a crank no start. EKPS was replaced and the car left, came back a while later same issue crank, no start. EKPS was dead again... further diagnosis found the ground wire was loose. The ground was tightened and the EKPS replaced again, car didn't come back.

[sapote]

In this case, OP measured pin11 of DME and no 5v or higher to turn on the pump relay.

OP, disconnect the relay (in the trunk) connector, then measure Connector pin1 (or DME pin11) when turning on ignition. In case the relay was shorted it could short out pin11.

[gheorghe]

I've seen the coil ground loose in the past and it cause the EKPS to fail. Car was in the shop for a valve adjustment, came back on the tow truck with a crank no start. EKPS was replaced and the car left, came back a while later same issue crank, no start. EKPS was dead again... further diagnosis found the ground wire was loose. The ground was tightened and the EKPS replaced again, car didn't come back.

Hi George, thanks for the heads up, it confirms the fuel side of the vehicle is affected by missing this ground. In my case, I do not know how to fully test the EKP but I have tested everything around it and I am leaning toward the DME as being the cause. I have continuity from DME X60002 pin 11 all the way back to the EKP pin 1 (same wire). I can manually prime the pump by jumping pin 6 and 2 on the EKP and start the car but I am not getting more than 0.5V on PIN 1. With the Key in Position 2 fuel pump does not prime.
Actually, priming the car manually by jumping the pins caused something interesting this weekend, typically doing this will start the car for 10-20 sec and then die off, but during one test, the car stayed running. I was able to back probe pin 1 at the EKP and the most voltage I was able to see was 1.2V with the car running. I known this is a PWM signal but I was told pin1 at the EKP should have at least 5V when there is signal from the DME.
Can anyone confirm with a DVOM what voltage they see at the EKP Pin 1 when they put the key in Position 2 before starting and what voltage they see when the car is running?

[gheorghe]

In this case, OP measured pin11 of DME and no 5v or higher to turn on the pump relay.

OP, disconnect the relay (in the trunk) connector, then measure Connector pin1 (or DME pin11) when turning on ignition. In case the relay was shorted it could short out pin11.

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. I see this voltage till the ECM relay kicks off and then the voltage goes to 0V which I expect.
If anyone would be able to back probe their EKP relay pin 1 under a couple circumstance (engine off key in position 2 and engine running) it would be a huge help.

[sapote]

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. I see this voltage till the ECM relay kicks off and then the voltage goes to 0V which I expect.
If anyone would be able to back probe their EKP relay pin 1 under a couple circumstance (engine off key in position 2 and engine running) it would be a huge help.

This confirms the DME failed to output 5v or higher during pump priming.

[George Hill]

Off the top of my head, IIRC the DME pulse width modulates the EKPS so checking voltage with a DVOM isn't going to be very accurate. I'll send you a EKPS if you want to try it, send me a PM.

[t3ddftw]

Just to add to the sample pool, I also forgot the coil pack ground once and the EKPS was what ended up causing my crank but no start. It also blew out the relay for the A/C.

-Ted

[sapote]

Off the top of my head, IIRC the DME pulse width modulates the EKPS so checking voltage with a DVOM isn't going to be very accurate. I'll send you a EKPS if you want to try it, send me a PM.

Don't think the pump needs to be modulated with PWM control as there is no reason for doing so. Pump already has pressure regulator. I would make more sense to have a pressure feedback sensor signal to the DME then it could control the pump speed to regulate the pressure.

[sapote]

Just to add to the sample pool, I also forgot the coil pack ground once and the EKPS was what ended up causing my crank but no start. It also blew out the relay for the A/C.

-Ted

When the 15Kv has no path to discharge, it will zap to anything that have a path to the ground, direct or indirect, and damaged them. This cable is easily overlooked when we're excited to start the engine up after the valve cover is closed.

[George Hill]

Don't think the pump needs to be modulated with PWM control as there is no reason for doing so. Pump already has pressure regulator. I would make more sense to have a pressure feedback sensor signal to the DME then it could control the pump speed to regulate the pressure.

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'm not saying the DME isn't fried, I'm just saying that my experience points to a bad EKPS. I'm not sure why it takes out the EKPS, maybe the coils and fuel pump control share some internal circuit or what not but we'll know soon enough.

[sapote]

I believe the EKPS is just a semiconductor relay as oppose to mechanical relay used outside US. One reason I can think up is using electronic relay has no potential of generating sparks by the breaker point, which could cause an explosion in highly combustible gas. Electronic relay can be operated just like the old mechanical relay, not PWM control signal needed. The only reason to use PWM control is when it needs to vary the variables, such as speed (radiator fan), pressure, flow rate (cabin heater coolant).

[George Hill]

I believe the EKPS is just a semiconductor relay as oppose to mechanical relay used outside US. One reason I can think up is using electronic relay has no potential of generating sparks by the breaker point, which could cause an explosion in highly combustible gas. Electronic relay can be operated just like the old mechanical relay, not PWM control signal needed. The only reason to use PWM control is when it needs to vary the variables, such as speed (radiator fan), pressure, flow rate (cabin heater coolant).

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 pump supplies fuel when it receives operating voltage from the fuel pump module (EKPS). The DME relay supplies voltage to the EKPS (M3- located in the trunk above the RR wheel well, Vert - behind the RR interior trim panel).

The DME controls the activation of the fuel pump module. After the ignition is switch ON, the DME provides voltage for the EKPS and the voltage is maintained (PWM) with the presence of the engine speed signal.

The high output fuel pump is utilized to match the fuel supply demands of the S54 engine (5 bar). The DME will cycle the voltage signal (0-120HZ) to the EKPS. The EKPS will cycle the voltage to the pump (to reduce the speed). The fuel pump will operate at low speed during idle and part load. The pump will run at full speed during start-up (approx 20 sec) and full load.

The power to the EKPS will be switched off in the event of an airbag activation. The MRS III control module will signal the DME over the K-Bus and CAN bus for this purpose."

[sapote]

I can't decide if you are trolling or not... the EKPS and FP relay are both located inside the passenger compartment

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: