Starter motor not cranking

[ga41]

Well... I wen't for a local forum meet/track day today. All was well with the car, started up fine, drove about an hour and a half to the meeting point with a stop in between to gather a few more participants and headed there.

Parked and turned the engine off but when i came back to it to go for my track session it wouldn't crank the engine... Thought it was a dead battery and the guys there helped me jump-start it. It fired up OK and i left it running until my 20min session. I thought it must've charged OK by then so after i got out of the track i parked it again as usual.. Came back 30min later and the same thing... Someone had a booster there so it was easy to start it up once again, by then i thought it wasn't worth the hassle so i returned home. Parked in garage, turn off engine, turn on engine immediately and yet again it would not crank at all, not a single engine revolution.

My first thought is dead battery but the weird thing is that the radio, lights, windows still worked. Shouldn't they remain without power too? Perhaps something else is causing it?

 

[Stuart Truman]

Check the earth connector at both ends. This can happen when the connection is bad, it can't cope with the current so radio etc all works but no starter. Do you get a "click"?


Tapatalking...

 

[ga41]

Check the earth connector at both ends. This can happen when the connection is bad, it can't cope with the current so radio etc all works but no starter. Do you get a "click"?


Tapatalking...

Yep, a click but no cranking. Checked the battery leads in the back and one was just very slightly loose so i tightened it, didn't make any difference. Where are the grounds leads to check?

 

[Stuart Truman]

Never had to do this on the zed, but had this exact problem on another car. Someone on here will probably know exactly where the earth lead hits the body. Also check the leads on the starter motor itself.


Tapatalking...

 

[ga41]

Gotcha. Will check that out tomorrow.

 

[Newbers]

Hey GA41, I had a very similar problem. On the front bulkhead there is a terminal which can be used for jump starting under the bonnet. You will see there are a couple of big heavy red wires coming out of it (one to battery, others to alternator and starter). I didn't see how this failed (I presume there was a loose connection) but BMW wouldn't let me take it home as they said it was glowing red! Part was only £11 + 1 hour.

I'm sure this is an easy fix but what ever you do disconnect the battery in the boot first!

Let me know if this fixes it.

 

[cj10jeeper]

I'd also put a meter across the terminals of the battery. Might be a dead cell. Ensure it's well over 12v. With one dead it can be ok putting lights on but not enough to crank the engine. Test battery again with engine running and the voltage should somewhere from 13v to 14v if charging circuit working.

If you have some heavy jump leads you can connect from the engine to the ground on the wing to eliminate the starter earth as being at fault too. Starter live - you have to get to it

 

[EdButler]

Yep sounds just like a dead battery cell like CJ said. It should read about 12.8v without the engine running. The starter should be fine if it can be cranked with a booster/jump.

The car doesn't need the battery at all once the engine is running, thanks to the alternator, which can provide ~150 Amperes.

 

[ga41]

It was the battery after all! Don't have a multimeter myself but had it tested and it was definitely dead, new Bosch one in and the car is as right as rain. It was just its time i guess. Think it was the original one too.

 

[cj10jeeper]

It was the battery after all! Don't have a multimeter myself but had it tested and it was definitely dead, new Bosch one in and the car is as right as rain. It was just its time i guess. Think it was the original one too.

Glad you resolved it Always best to start with the obvious eliminate that first. I'd invest in a multimeter. They only cost a few Euros and are really useful

 

[mus_oz]

Hi guys,

I have the same issue.

But, with my case, I have a multimeter, and it is reading about 11.8Volts before trying to start and the battery (original) is rated at 12V anyways. So this makes me think the battery isn't the problem. OR am I missing something?


I can jump start it and it is fine. But after 2 hours, sitting, doing nothing, it won't start. LEave it for about 10mins, it will start.


Any ideas guys? I don't want to change battery and find out that isn't the issue...

 

[fixit man]

Hi guys,

I have the same issue.

But, with my case, I have a multimeter, and it is reading about 11.8Volts before trying to start and the battery (original) is rated at 12V anyways. So this makes me think the battery isn't the problem. OR am I missing something?


I can jump start it and it is fine. But after 2 hours, sitting, doing nothing, it won't start. LEave it for about 10mins, it will start.


Any ideas guys? I don't want to change battery and find out that isn't the issue...

Hi,
Battery should be about 12.6 volts fully charged, still doesn't mean the battery is goosed , could be the alternator is not charging it or parasitic drain, check battery voltage while the engine is running, should about 14 volts

 

[mus_oz]

Hiya,

Yh when the engine is running, its reading about 14.4 - 14.8 Volts.

I don't suppose this is too much voltage i.e. regulator issue?

 

[cj10jeeper]

Hiya,

Yh when the engine is running, its reading about 14.4 - 14.8 Volts.

I don't suppose this is too much voltage i.e. regulator issue?

Based upon what you're saying the charge voltage is perfect in the range you give. No alternator issues

The voltage on your battery is way too low. Should as posted be 12.4 to 12.6 when resting. 11.8v without doubt shows your battery has a dead cell and needs replacing as drain could not kill it so quick.

Get a new battery and you'll be just fine.

 

[NMC100]

Hi ga41

I had this problem almost a year ago. Car would start from cold everytime but if ran for more than 20 mins and switched off wouldn't then start for at least an hour. I persevered for a few weeks then had a new starter motor fitted under warranty.

Seems to be a slow failure of the solenoid.

 

[mus_oz]

I had to jump start my car just now. I decided to go to Bosch Technical Centre to get the battery checked. Result: "Battery need replacing" message on their computer. Anyways, changed the battery now. It starts now. However, I will monitor the issue. I am not entirely convinced :|

 

[cj10jeeper]

I had to jump start my car just now. I decided to go to Bosch Technical Centre to get the battery checked. Result: "Battery need replacing" message on their computer. Anyways, changed the battery now. It starts now. However, I will monitor the issue. I am not entirely convinced :|

Why are you not convinced? All the readings point to this and a test shows the battery needs replacing and after replacing it works.

Couple the old battery to a charger and then leave it standing. Should see the voltage drop to 11.x in a few hours

 

[mus_oz]

I am not convinced because just a 0.4V drop across the battery doesn't allow the engine to be cranked... I would understand if it was 2 to 3 V drop that wouldn't crank the engine, but 11.x Volts isn't enough... explanation would be good...

 

[Mister T]

I am not convinced because just a 0.4V drop across the battery doesn't allow the engine to be cranked... I would understand if it was 2 to 3 V drop that wouldn't crank the engine, but 11.x Volts isn't enough... explanation would be good...

Had exactly the same issue with my Z3.

It's not the voltage that's the issue, it just can't supply enough current (internal resistance too high).

 

[cj10jeeper]

I am not convinced because just a 0.4V drop across the battery doesn't allow the engine to be cranked... I would understand if it was 2 to 3 V drop that wouldn't crank the engine, but 11.x Volts isn't enough... explanation would be good...

12.6v 100% charged
12.4 = 90%
12.2= 60%
11.9 = 40%
11.75 = 30%
11.3 = 10%
10.5 = flat

Put another way at 11.8v you are around about 35% charged, so that explains why it won't start. I'll bet it also drops to nearer 11v when cranking.

Fact that it goes straight to 14.8 when running tells me the battery is flat ie holding no charge but alternator is working fine. If the alternator was faulty there would be no useful charge generated so the car would grind to a halt minutes after the jump start, but you don't say that happens.

As with all things though it's diagnosis from a distance that makes it near impossible to be sure of anything and of course you could be correct re the alternator. I just doubt that.