Intermittent starting

Meeko · Post by **Meeko** » Mon Feb 25, 2019 6:01 pm

Hi all,

My Z4M Roaster takes a few turns of the key to start. All ignition lights come on, and when you turn the key to fire there is the sharp clunk which I presume is the solenoid, and then nothing. Usually on the second or third attempt the engine turns over and all is well.

The battery got quite low over winter but after a few runs seems to be good now. I've read it might be ingition switch, but seeing as I get the dash lights and the solenoid energises, is it more likely to be a dodgy starter motor?

I've got a BMW warranty with £250 excess. Might attempt myself if it's easy?

Cheers,

Meeko

Adam D · Post by **Adam D** » Mon Feb 25, 2019 9:28 pm

Cheaper to swap the battery first if it’s the original.

Mangozac · Post by **Mangozac** » Mon Feb 25, 2019 9:44 pm

If it eventually fires then I doubt it's the battery. I think you're on the right track with the starter motor Meeko (more specifically the starter motor solenoid contacts).

Bing · Post by **Bing** » Mon Feb 25, 2019 9:45 pm

Adam D wrote: ↑Mon Feb 25, 2019 9:28 pm Cheaper to swap the battery first if it’s the original.

This first, maybe... I swapped out my original battery not long ago - it lasted 12 years ! But it was slowly taking more cranks to start, and with the cold weather looming I just bit the bullet. Remember that if a battery’s charge gets too low it can end up borked and no amount of charging will rescue it.

Edit - I am not sure if poor battery voltage can affect other things like the alternator or starter motor over time as well - can anyone answer that ?

Mangozac · Post by **Mangozac** » Mon Feb 25, 2019 11:56 pm

Bing wrote: ↑Mon Feb 25, 2019 9:45 pm Edit - I am not sure if poor battery voltage can affect other things like the alternator or starter motor over time as well - can anyone answer that ?

The alternator would spend more time trying to charge a dead battery, so theoretically it's additional wear. Whether in practice it's enough to shorten the alternator lifespan I'd be sceptical of. A lower battery voltage won't hurt the starter but again theoretically you're adding additional wear because you're cranking more.

Post by **srhutch** » Tue Feb 26, 2019 7:57 am

Don’t our alternators charge all the time?

I know they don’t with modern cars with stop/start and regen features, but ours are old school aren’t they?

Mangozac · Post by **Mangozac** » Tue Feb 26, 2019 10:20 am

srhutch wrote: ↑Tue Feb 26, 2019 7:57 am Don’t our alternators charge all the time?

I know they don’t with modern cars with stop/start and regen features, but ours are old school aren’t they?

No, they're modern "smart" alternators. There is a data line between the DME and the alternator for fault detection and so the DME can tell it when it's allowed to charge and load up the engine.

Meeko · Post by **Meeko** » Tue Feb 26, 2019 4:04 pm

Thanks for your replies everyone. It's getting more frequent now, but when it actually does start the engine turns over quickly and the headlights don't dim so I don't think it's the battery. ? I've read the signal from the EWS (immobiliser) when live activates the starter, but are the solenoid and start motor activated by this single signal? i.e. the EWS and ignition switch are likley to be OK?

Mangozac · Post by **Mangozac** » Tue Feb 26, 2019 9:42 pm

Meeko wrote: ↑Tue Feb 26, 2019 4:04 pm Thanks for your replies everyone. It's getting more frequent now, but when it actually does start the engine turns over quickly and the headlights don't dim so I don't think it's the battery. ? I've read the signal from the EWS (immobiliser) when live activates the starter, but are the solenoid and start motor activated by this single signal? i.e. the EWS and ignition switch are likley to be OK?

I agree, it's definitely not the battery.

While an issue with the relay inside the EWS unit is possible, I think it's the least likely option at play. What you're describing is fairly synonymous with a failing starter motor. The starter and solenoid are all one item (the solenoid is on the end of the starter) so one doesn't activate without the other. I know access is difficult but try giving the starter a whack with a non marking hammer while attempting to start - the shock can bring it to life and will prove that it is indeed the starter that's faulty.

mad4slalom · Post by **mad4slalom** » Wed Feb 27, 2019 7:23 pm

Hi meeko and all. I am still having the same symptoms, always goes eventually after a few attempts and some times first go, I can hear a clunky type click which bmw tech says indicates that power is getting through to the starter most probably. And says the s54 engined cars suffer from failing starters. Think I will buy one ready .

john-e89 · Post by **john-e89** » Wed Feb 27, 2019 7:37 pm

Took the air box off mine yesterday to change my starter motor, it’s by far the easiest way rather than scrabbling around underneath the car.

GuidoK · Post by **GuidoK** » Wed Feb 27, 2019 8:37 pm

Meeko wrote: ↑Tue Feb 26, 2019 4:04 pm it actually does start the engine turns over quickly and the headlights don't dim so I don't think it's the battery.

On these cars the biggest chance is worn brushes in the starter motor.
Otherwise the ignition switch.

mad4slalom · Post by **mad4slalom** » Wed Feb 27, 2019 8:42 pm

john-e89 wrote: ↑Wed Feb 27, 2019 7:37 pm Took the air box off mine yesterday to change my starter motor, it’s by far the easiest way rather than scrabbling around underneath the car.

Did that take you long john?

john-e89 · Post by **john-e89** » Wed Feb 27, 2019 10:11 pm

mad4slalom wrote: ↑Wed Feb 27, 2019 8:42 pm
john-e89 wrote: ↑Wed Feb 27, 2019 7:37 pm Took the air box off mine yesterday to change my starter motor, it’s by far the easiest way rather than scrabbling around underneath the car.
Did that take you long john?

No it’s quite straightforward Mad4, mine hasn’t been off before so had the original clips on the intake trumpet rubbers, they’re tight and you need to squeeze them together to release them or prise them carefully. I’ll be using stainless steel jubilee clips to refit so don’t worry too much. Then it’s just a case of undoing the air pipes and maf sensor, two nuts under the air box and it’s off. Trust me it’s soooooooo much easier than going from underneath. If you’ve not done it before half an hour will see it off.

mad4slalom · Post by **mad4slalom** » Thu Feb 28, 2019 9:07 pm

john-e89 wrote: ↑Wed Feb 27, 2019 10:11 pm
mad4slalom wrote: ↑Wed Feb 27, 2019 8:42 pm
john-e89 wrote: ↑Wed Feb 27, 2019 7:37 pm Took the air box off mine yesterday to change my starter motor, it’s by far the easiest way rather than scrabbling around underneath the car.
Did that take you long john?
No it’s quite straightforward Mad4, mine hasn’t been off before so had the original clips on the intake trumpet rubbers, they’re tight and you need to squeeze them together to release them or prise them carefully. I’ll be using stainless steel jubilee clips to refit so don’t worry too much. Then it’s just a case of undoing the air pipes and maf sensor, two nuts under the air box and it’s off. Trust me it’s soooooooo much easier than going from underneath. If you’ve not done it before half an hour will see it off.

right then , collecting starter nxt wed so will look forward to doing that. Thanks for your helpful advice

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