Weak starting problem

[pbonsalb]

I parked my 08M3 with 93k miles for 10 days and it was very slow cranking after so I gad to jump it. Charged the battery. Same problem. Changed the battery and charged it. Same problem. Changed the alternator and charged the battery. Same problem. Reset battery adaption.

Cranks fastest but still on slow side the first start. Once hot, upon restart the cranking is slower. Battery voltage with engine on is around 13.3.

Before I changed alternator, I got a code for alternator missing.

Any ideas? Starter? IBS cable?

[///M Power-Belgium]

EDC ?

[pbonsalb]

My car does not have EDC. I tested voltage after the slow cranking and with the engine off it was 12.56. That means the battery is fine. Must be the starter.

[///M Power-Belgium]

Originally Posted by pbonsalb

My car does not have EDC. I tested voltage after the slow cranking and with the engine off it was 12.56. That means the battery is fine. Must be the starter.

Indeed . But it can be also a failing starter solenoid with part number # 12417836450 => https://www.ecstuning.com/b-genuine-...h/12417836450/

[sibhusz06]

To truly check a batteries condition, you must check the voltage under load when cranking, the current draw causes a voltage drop which is indicative of the battery condition. Just make sure it doesn't drop below 11.0-11.5vdc.

Also check to make sure all your starter/battery cables and connections are solid with no corrosion or high resistance.

Could be your starter also, mine failed on a 328xi, in that case the cranking became slow and sluggish and finally failed with no crank.

[pbonsalb]

I have been a bad mechanic on this job. The battery was less than a year old so I had it warrantied without even load testing it. Then I changed the alternator, which is ok since it was 10 years old and the new valet was only $1408. Now I will be replacing the starter, and the Bosch rebuilt was only $110. My garage is under renovation so all my tools are in storage and I am working outside with basic hand tools and not doing as good a job. Pretty sure it’s the starter or solenoid now and the solenoid cost more than the rebuilt starter with solenoid.

[pbonsalb]

New starter spins faster. Problem appears fixed. Might have just been solenoid but the price for a Bosch rebuilt with solenoid was less than the price of the solenoid. Pain to change. I did my plugs again while I was in the area. The center electrodes were oval at 30k miles instead of round so they were due. Ideally I would have done valve cover gaskets but I did not have them in hand and my garage is still being renovated and tools are still in storage so I was working outside with limited tools.

[tmak90]

I’m having similar issues on cold starts. Starts are long and struggle but after that it runs fine, just notice it only occurs when temps are cooler and on initial cold starts. Tried to scan for codes but got nothing. Could it possibly be my low pressure fuel sensor or most likely the starter?

[pbonsalb]

My cold starts were fine. Hot starts were my issue, due to increased resistance. I also added an extra ground wire and that yielded further improvement so I will replace all my grounds once my garage is done and I set up my lift.

If weak cold starting, I would suspect battery since cold starts require more power than hot starts. But after my own misdiagnosis, I think you should get feedback from more than me.

[tmak90]

My battery is fairly new, about 3-4 months old. Didn't find any errors when checking diagnostics...Is it possible that the starter can be going out without giving any kind of code?

[pbonsalb]

If it’s cranking fast when cold but not catching then it’s not the battery and could be something fuel or spark related. Are you using a good code reader with bmw specific software?

[tmak90]

It's struggling to crank when cold. If I leave the car for 30 mins or so and come back, it starts with no issue, just on the initial cold start. I was thinking it may have been cause I used the carly app to register my battery few months ago and it probably didn't register it correctly. I only have the carly code reader and didn't find any codes that came up when running the diagnostics.