Random question about key cranking

[Davelaz23]

Hi everyone! Decided to pull my 4.6 out of the garage and start using it since it’s time to put away my e39 I’ve always noticed that when I start my M5 I have to hold the key while cranking until it starts versus with the X5, I just turn the key once, let it go and it cranks on its own until the engine fires up. Does anyone have more info about that, or if other models do it as well? It’s just one of the many interesting quirks I’ve always wondered about..


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[Clavurion]

Originally Posted by Davelaz23

Hi everyone! Decided to pull my 4.6 out of the garage and start using it since it’s time to put away my e39 I’ve always noticed that when I start my M5 I have to hold the key while cranking until it starts versus with the X5, I just turn the key once, let it go and it cranks on its own until the engine fires up. Does anyone have more info about that, or if other models do it as well? It’s just one of the many interesting quirks I’ve always wondered about..

This automatic start control (or convinient start) is implemented on engine control unit of V8 engines (start motor activation via separate relay). I think E39 M5 should have it too.

[andrewwynn]

Year of the m5?

[Davelaz23]

Originally Posted by Clavurion

This automatic start control (or convinient start) is implemented on engine control unit of V8 engines (start motor activation via separate relay). I think E39 M5 should have it too.

Very interesting thanks for the info! I’ll have to try again but I’m almost 100% positive my e39 won’t do it. I’m now curious if this was a quirk that BMW felt like throwing in or if this was for any particular reason


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[Davelaz23]

Originally Posted by andrewwynn

Year of the m5?

2001


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[andrewwynn]

I think the feature has always been on the X5 so it is surprising not M5 same vintage. Look in your manual see if it's mentioned in each.


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[Davelaz23]

Originally Posted by andrewwynn

I think the feature has always been on the X5 so it is surprising not M5 same vintage. Look in your manual see if it's mentioned in each.


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Ok all figured out. Convenience starting feature is only on 8 cyl models with automatic transmission. It appears in the manuals for both the e53 v8, and e39 540iA manuals. Specifically notes for automatic transmissions only, which is why it’s not on my M5.


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[Clavurion]

Originally Posted by Davelaz23

Ok all figured out. Convenience starting feature is only on 8 cyl models with automatic transmission. It appears in the manuals for both the e53 v8, and e39 540iA manuals. Specifically notes for automatic transmissions only, which is why it’s not on my M5.

I knew this feature on other V8 models was on automatic version only (no separate start relay on manual models). On wiring diagrams M5 (MSS52) has a separate start activation relay (same one which controls automatic start) but the function seems to be just to prevent starter activation if clutch pedal is not depressed.

[andrewwynn]

Mystery solved good job


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