SMG pump priming noise with the salmon relay and 40A fuse removed?

[sapote]

02/2006 ZCP IB 74K miles.
I already had removed the fuse and the relay but when opening the door or trunk I heard a light buzzing noise for about 5sec. What is it as it cannot be the pump priming?

[eacmen]

Fuel pump? Where does it sound like its coming from?

[Arith2]

Could possibly be the ABS since it is in close proximity. Unless you have the fuel pump unplugged, it could just be resonating sound down the line. I disconnected my fuel line and opened the door out of curiosity. It spit fuel for about 5 seconds.

[sapote]

I thought fuel pump only primes when the key turned on. No key involved here but only open the doors or trunk.
The sounds seems to be under the console/dash or where the SMG pump is.

It sounds like Ezzzz, higher pitch than the fuel pump I think. After whatever was primed, close and open the door again within a minute doesn't make it running again, but after 5 or 10 minutes, it will prime again when doors or trunk opened.
I always thought this was the SMG pump priming until today I removed the 40A fuse and it still primed, then removed the salmon relay and it still primed. The car is all original stock.

[sapote]

So the buzzing noise is not the SMG pump priming, as the starter doesn’t crank until I installed the fuse and relay to build up the oil pressure. I don't know what is the noise; maybe it's the ABS/DSC pump priming, but non-M cars never have this motor priming just by opening the doors or trunk. Anyone can verify the noise with fuse and relay removed?

[Drewrivera]

I always thought it was the SMG as 6mt's don't prime when touching the doors like that.

[sapote]

I always thought it was the SMG as 6mt's don't prime when touching the doors like that.

Right. so it's not abs/dsc as it should be the same for 6MT or SMG. So it's a mystery why the SMG makes noise when doors/trunk opened with no fuse and relay.

[eacmen]

Right. so it's not abs/dsc as it should be the same for 6MT or SMG. So it's a mystery why the SMG makes noise when doors/trunk opened with no fuse and relay.

To narrow it down maybe unplug the large connectors from the SMG ECU in the e-box? Maybe there is some kind of parasitic voltage being supplied from the ECU?

[sapote]

For sure the pump can't run with the relay unplugged, but I always thought that's how the pump sounds. I will use INPA to activate the pump and listen to the sound.
Unless the SMG try to activate the clutch or the actuator and so that could be the sound of the control solenoid valves even with no oil pressure.

People with SMG have no similar noise like this?

[eacmen]

Could be the sound of a failing solenoid? When I have unplugged the relay I have not gotten any sound like this.

[oceansize]

I can't comment as whenever I work on the car I remove the negative battery terminal. You can do this to fire up the motor without the relay since you are simply wanting to hear the noise it makes.

[sapote]

Could be the sound of a failing solenoid? When I have unplugged the relay I have not gotten any sound like this.

I have been driving the M3 daily 40 miles round trip since the Porsche got hit, and it runs flawlessly. It's just I don't understand what makes the noise even with fuse and relay removed.

[sapote]

I can't comment as whenever I work on the car I remove the negative battery terminal. You can do this to fire up the motor without the relay since you are simply wanting to hear the noise it makes.

This will work, but ideally I want to hear the noise with the hood closed and the driver door opened exactly the same condition to help identify the noise.
Also, jumping the relay as you did -- can this cause the pressure too high? I know the system has the pressure sensor and so the controller might read the sensor and cut off the pump when the pressure is reached, but is there a pressure relief valve in the system to prevent over-pressure?

[eacmen]

Yes the SMG pump has a high pressure relief valve.

[Pnick]

Could it be the E-box fan? I read somewhere when I still have mine that when the bearings of the E-box fan is starting to fail that it gives this high freq. sound like an SMG pump priming...
Try removing the fuse F3 - 20A in the in the engine electronics fuse carrier. It's for the E-box fan and some other components. See if still happens.