No Crank no Start

[wolfalanj]

Hey ya’ll

So having a weird one. So I did all the fluid changes on my Z4m last week, and since then the car is refusing the start. Originally we had removed the ground cable that comes off the what I believe is the Vanos capacitor l, and forgot to put it back so car wasn’t starting, after we put it back it started one time but since has stopped. Here is what has been done so far.

Replaced battery, replaced ignition switch, removed starter and bench tested it and the motor spins, the solenoid is not pulling the pin back however but the gear does spin.

When the starter is back in the car, it doesn’t even spin, I tested with multimeter and the starter has the constant 12v as rest as it should.

I also checked the EWS module and didn’t notice anything out of place, I downloaded ISTA software I want to see if anything happening when you try to start the car, I do hear the fuel pump engaging so not sure if that means the immobilizer disengaged with the key or not I have a feeling that means it’s good? I am kind of stuck at this point I made appt for this week with local BMW guy but wanted to see if I could get it working myself.

This happened once before on September 2021, they had replaced the starter and that didn’t help, they said it ended up being a corroded wired which I think might have been at the ignition switch but nothing in there looks corroded now.

Any help is much appreciated thanks!

 

[enuff_zed]

EWS allows the motor to crank but doesn’t allow fuel or spark if it is out of synch with the DME, so it’s not that.
If the starter works on the bench but not on the car then it’s most likely to be a connection issue with that, or an earth.

 

[wolfalanj]

Thanks how do you verify connection to starter it is getting voltage what else would I check? And for ground which one should I be checking?

 

[enuff_zed]

Thanks how do you verify connection to starter it is getting voltage what else would I check? And for ground which one should I be checking?

According to this diagram, you have the two big fat red cables that both go to the large connector, then the smaller wire from the EWS that goes to the smaller connector.
Earthing is through the body of the starter motor to the engine block. Therefore you should confirm you definitely have a good earth from the engine to the chassis, and also that you get a signal from the EWS.

 

[wolfalanj]

Therefore you should confirm you definitely have a good earth from the engine to the chassis, and also that you get a signal from the EWS.

Is there an easy method to test signal from the ews? I know it's the tiny black wire on the starter, and I will check that ground cable we reinstalled once again as well.

 

[enuff_zed]

Therefore you should confirm you definitely have a good earth from the engine to the chassis, and also that you get a signal from the EWS.

Is there an easy method to test signal from the ews? I know it's the tiny black wire on the starter, and I will check that ground cable we reinstalled once again as well.

Not sure tbh.
Looks like it energises the relay in the starter solenoid, so probably just a simple 12v feed when you turn the key?

 

[wolfalanj]

Not sure tbh.
Looks like it energises the relay in the starter solenoid, so probably just a simple 12v feed when you turn the key?

You mean like put the multi meter on the starter solenoid as you turn the key?

 

[enuff_zed]

Not sure tbh.
Looks like it energises the relay in the starter solenoid, so probably just a simple 12v feed when you turn the key?

You mean like put the multi meter on the starter solenoid as you turn the key?

I should point out that I'm strictly airframes and engines! Anything involving electrickery is not my strongest suit, but That's what I'm thinking, yes.
Or disconnect the lead from the EWS, and check it for voltage (earthing to the starter body) as you turn the key. If that shows nothing, try again, but earthing to the chassis. If it shows voltage then, you are looking at an earth issue somewhere.

 

[wolfalanj]

Not sure tbh.
Looks like it energises the relay in the starter solenoid, so probably just a simple 12v feed when you turn the key?

You mean like put the multi meter on the starter solenoid as you turn the key?

I should point out that I'm strictly airframes and engines! Anything involving electrickery is not my strongest suit, but That's what I'm thinking, yes.
Or disconnect the lead from the EWS, and check it for voltage (earthing to the starter body) as you turn the key. If that shows nothing, try again, but earthing to the chassis. If it shows voltage then, you are looking at an earth issue somewhere.

Thanks I’ll give it a shot!