(Yet another) M42 top end refresh and engine reseal (mid-2021)

[bmwman91]

Actually I was incorrect. The car would (in theory) run with the battery disconnected (if the engine was already running when you disconnected it), although there is a decent risk of damaging all sorts of electronics that way. The battery damps the high voltage spikes generated by the alternator and serves as a load on the system which helps the voltage regulator to stay in its linear operating region.

If the car was stalling immediately when disconnecting the battery, then it could mean that the alternator/VR were dead. It could also be that the undamped electrical noise from disconnecting it was interfering with the ECU. Anyway, a fresh battery and VR should hopefully fix your issue. If you get both of those in and find that the battery charge indicator stays on after turning off the engine, then you also need a new or rebuilt alternator because the diodes are pooped.

[jsnppp]

Update -

Got the new VR today. Plugged it in and no change.

* Dashboard battery light remains off when turn key.
* No change to dashboard light when starting the motor

I had pulled the cluster and confirmed that the bulb does work. I can inspect the circuit board to make sure no other shenanigans are going on.

I haven't yet bought a new battery, but I DID swap in a different used battery tonight to check behavior. No change.

While both batteries are not new, I still have been starting and driving on the first one for a bit of time. What I'm saying is that the original battery isn't completely shot. That being said, I'll get a new one.

I may also go to autozone or what not and have it tested.

Feels like there may be something else going on here though. With all my cluster issues it warrants my time to peek into it again to see what I find. There isn't an alternator fuse, or some other junction in the middle that could go wrong? I tested D+ and B+ behavior and they appear ok..

~Jason

[monty23psk]

Take the battery to an autoparts place to have them check the health. While in theory, if you unplug the battery while car is running, it can stay on but the majority of the time it will die. The alt needs to charge battery and when it is open all weird things happen. With the battery disconnect, what voltage does it read? With the battery connected, turn the key to the position 2, does the battery light in the cluster turn on?

[jsnppp]

Take the battery to an autoparts place to have them check the health. While in theory, if you unplug the battery while car is running, it can stay on but the majority of the time it will die. The alt needs to charge battery and when it is open all weird things happen. With the battery disconnect, what voltage does it read? With the battery connected, turn the key to the position 2, does the battery light in the cluster turn on?

No battery light on the cluster with key in position 2. I checked the cluster bulb and it does work. Next step is to open the cluster to make sure it looks healthy inside.

I also checked that B+ at alternator reads battery voltage all the time. And checked that D+ is at 12v at the alternator with key in position 2.

Feels like something basic is going on.

Of course it could also just be the alternator is shot for another unknown reason.

[monty23psk]

Maybe ignitor cable is bad on the alternator. Look up the ETM to see what is happening. I believe it is simple. You can do a continuity test from the bulb socket to the alternator, I believe.

[jsnppp]

Maybe ignitor cable is bad on the alternator. Look up the ETM to see what is happening. I believe it is simple. You can do a continuity test from the bulb socket to the alternator, I believe.

I'm thinking the same. I may not be reporting the behavior correctly.

To my understanding, the D+ terminal should read ground when key is in position 2. This completes the other side of the dash bulb 12v (and lights the dash bulb). When the engine is running, the D+ terminal should switch to 12v (and so the bulb goes out).

I wasn't thinking when I tested it before. Tomorrow I'll do it again.

Tonight I'll review the ETM.

+Jason

[jsnppp]

Well that sucks.

I found that the D+ terminal was loose (it spun!).

Separated the two halves and indeed found the wire broken off internally. I then found pretty tired internals, flaking wires, lots of corrosion.

I tried to solder the wire back on and it broke!

So, while I am sure there are other issues, I am in need of a new alternator. If anyone has one available, let me know! Otherwise, Internet here I come.

Cheers,

Jason

[jsnppp]

Ordered a new Bosch from FCP euro. Arriving next week!

I'll pull the cluster board to make sure nothing seems wrong with the battery light wiring.

And continue on with the little things the car needs (passenger door handle feels loose, etc.)

[bmwman91]

Good stuff, glad you found a definitive answer. The snowball continues to grow lol. Fingers crossed for you that you will get to drive and enjoy the thing soon!

[jsnppp]

Thanks. I think it was you who wrote that restoring a 318is is like watching a bonfire of money.

Like Rainman, everything is $100.

All good, it's fun and we are learning a lot.

[vulteiv1]

Hey, I’m in the process of rebuilding my m42 too. I’m going through all of the nuts and bolts, but don’t recall where this locking bolt goes. Do you remember seeing it?

[jsnppp]

Hey, I’m in the process of rebuilding my m42 too. I’m going through all of the nuts and bolts, but don’t recall where this locking bolt goes. Do you remember seeing it?

Really good question, I know i've seen it but can't recall off top of my head. Let me look into that.

Perhaps someone else has an answer in the mean time!

Jason

[monty23psk]

Thanks. I think it was you who wrote that restoring a 318is is like watching a bonfire of money.

Like Rainman, everything is $100.

All good, it's fun and we are learning a lot.

I recommend you get some updated urethane bushings for mounting it as the rubber ones will deteriorate. The m42 being 4-cyl vibrates a lot. Just a suggestion.

[jsnppp]

I recommend you get some updated urethane bushings for mounting it as the rubber ones will deteriorate. The m42 being 4-cyl vibrates a lot. Just a suggestion.

Good call on that. I actually already have the rubber but it's easy to access and so I can retrofit it once I make my next order.

[jsnppp]

Really good question, I know i've seen it but can't recall off top of my head. Let me look into that.

Perhaps someone else has an answer in the mean time!

Jason

I'm still tracking where that bolt/holder went!