Constant 10v to fuel pump?

[FFWD]

EDIT: Looks like it's normal.

My M3 will crank but not start. When measuring the two connector holes for the pump, I get 10v with the key out and passenger door open. But it goes to 12v for 2 seconds when I turn the key to "ON", then back to 10v, then 12v while cranking. I tried 2 different meters in case it was the meter. There shouldn't be any voltage going to it with the key out, right? What could be causing this, and I suspect this may be what killed my pump, so I'd like to fix it before replacing the pump.

[sapote]

The 10v could be the result of the relay floating output when off which is normal for FET power switch, meaning you should measure with the load (pump) connected ( then the 10v becomes ov as I expect).

[FFWD]

The 10v could be the result of erelay floating output when off which is normal for FET power switch, meaning you should measure with the load (pump) connected ( then the 10v becomes ov as I expect).

Sorry, not sure I understand what you mean - I should reconnect the connector to the pump? Then back-probe the wires? Most of the video's I've seen show people measuring the connector disconnected, but then those were non-M E46's.

[FFWD]

OK, I get it now - I found this video of an actual E46 M3 pump, so it looks normal (for a bad pump).

https://www.youtube.com/watch?v=6vmzwEDTB1Q

[sapote]

For the YT video, 10v to the glove box light bulb should turn it on so I don’t know what he was talking about.
same for the pump, it should spin at 10v; if not then the connector was not delivering 10v to the pump two pin.

[FFWD]

In any case, I replaced my pump with the Hella version ($83 at Rock Auto with 5% off), and the car fired right up. Now it's just a question of how long this thing will last. Luckily this is no longer a daily driver as I work from home permanently now, and if it's nice enough to drive the convertible, it's nice enough to ride one of my bikes.