Bad Battery Cable or Battery Safety Terminal?

[tr3flip]

I'm going through a weird electrical gremlin on my E46 M3. I was getting a no crank, no start symptom after doing a top end rebuild on my S54. The car sat for three months while I did the rebuild. I was finally able to get the car to start by jumping it from the shock tower. However, the car will do the no crank, no start if I try jumping it directly from the battery. All the dash lights and accessories seem to work just fine and the car runs completely normal once started.

I've checked the grounds and even added a couple of extra ground wires to both the battery side and the front passenger chassis to engine side to eliminate the possibility of a bad ground. This leads me to think the positive battery cable from the trunk to the fire wall is bad or the battery safety terminal is slightly triggered. Unfortunately, that positive cable from the trunk to firewall is NLA from BMW. Has anyone else experienced anything similar? Should I make my own positive cable and eliminate the BST altogether?

A picture of the car for fun.

[ejendow]

I would check the state of the metal underneath the nut on the 12V post in the engine bay (PN 61138387540). I had a similar issue after working on something unrelated and had a no crank no start.

As a last ditch, I checked under the 19mm nut there and saw that the metal had a bunch of surface rust. Sanded it all off and the car started fine.

Not saying this is your issue, but definitely worth checking!

[tr3flip]

I would check the state of the metal underneath the nut on the 12V post in the engine bay (PN 61138387540). I had a similar issue after working on something unrelated and had a no crank no start.

As a last ditch, I checked under the 19mm nut there and saw that the metal had a bunch of surface rust. Sanded it all off and the car started fine.

Not saying this is your issue, but definitely worth checking!

It's worth a shot! I live near the beach and had this disconnected while doing the head work. I'll try sanding that connection today and report back. Thanks!

[Slideways]

What type and how old is the battery?

[tr3flip]

It's a full size Interstate Battery I purchased 18 months ago.

[tr3flip]

I would check the state of the metal underneath the nut on the 12V post in the engine bay (PN 61138387540). I had a similar issue after working on something unrelated and had a no crank no start.

As a last ditch, I checked under the 19mm nut there and saw that the metal had a bunch of surface rust. Sanded it all off and the car started fine.

Not saying this is your issue, but definitely worth checking!

Well shit, this ended up working! Thanks for the suggestion.

[ejendow]

Well shit, this ended up working! Thanks for the suggestion.

love it. glad it was an easy fix!