Z4 Coupe intermittent start issue

Z450 · Post by **Z450** » Wed Mar 13, 2024 2:07 pm

Hi

I have a recently acquired Z4 Coupe. Every so often the car will not start, all dash lights appear but no click at all.

From initial research, starter motor and ignition switch come up, and also possible key issue.

Going through the cars paper work it had a new starter motor 6 months ago. The fault happens with both keys. It also only seems to happen when the car is warmed up.

Any one had a similar issue?

Thank you

MEV Z4 · Post by **MEV Z4** » Thu Mar 14, 2024 12:02 am

Double check the Heavy cable that goes from the back of the Alternator - To the Starter Motor - To Bulkhead Mounted Terminal.

Check the connections are good and tight at ALL connection points. Remove / clean / retighten the cable at ALL points.

NOTE - The cable joins onto the Starter Motor and then a separate cable (On the same Starter Motor terminal) continues up to the bulkhead.

I had the same problem as it was loose there but wasn't obvious as it's hidden by the manifold and during my trouble shooting I waggled one cable which felt tight but the other one was loose. Just take them both off / clean and refit.

You'd get no click if that connection was loose as that's where the starter solenoid is. (Or maybe a click but no cranking?)

All the lights may come on (When you're driving?) because the alternator wont be connected properly and the battery will drain as you drive along - Soon you'll be under 9v and the computer wont like it and will light everything up.

I think the cable on your new starter motor has waggled loose / was never tightened up enough!

Sounds obvious but it took me ages to figure it out on my Z4 2.5........

AveZ4coop · Post by **AveZ4coop** » Thu Mar 14, 2024 11:27 am

I had the same issue and it was solved by replacing the ignition switch. Easy job and parts are cheap. Hope you solve it soon.

Z450 · Post by **Z450** » Thu Mar 14, 2024 11:39 am

Thank you for the replies.

I will be dropping it off to my local bmw specialist early next week so will ask about the starter motor being checked, if this looks all good then replace the ignition switch and see how we get on

Kenich · Post by **Kenich** » Thu Mar 14, 2024 4:10 pm

AveZ4coop wrote: ↑Thu Mar 14, 2024 11:27 am I had the same issue and it was solved by replacing the ignition switch. Easy job and parts are cheap. Hope you solve it soon.

Good to hear. Do you have the part number at all.

the gill · Post by **the gill** » Fri Mar 15, 2024 12:26 am

I had similar issues some years ago and changed the starter motor - it didn't fix the issue which was the ignition switch. Very easy DIY job to replace and it was fixed. Moral of the story - don't replace starter motor until you have checked ignition.

Z450 · Post by **Z450** » Fri Mar 15, 2024 8:41 am

Many thanks for everyone’s in put.

For those of you who had this issue, did you find it occurred, when the car was warm only? It has not happened when the car is cold.

AveZ4coop · Post by **AveZ4coop** » Fri Mar 15, 2024 9:07 am

Z450 wrote: ↑Fri Mar 15, 2024 8:41 am Many thanks for everyone’s in put.

For those of you who had this issue, did you find it occurred, when the car was warm only? It has not happened when the car is cold.

It started to happen randomly and steadily got worse, it wasn't related to temperature. It sounds like yours only happens when the engine is warm, which could point to starter motor/cable-terminal issue in the engine bay?

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