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      11-30-2017, 12:42 AM   #1
M3MPH1S
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DIY engine ground cable replace

This is a potential solution to issues with your car not starting. Sometimes the ground cable will get corroded or even damaged.

This is a very easy DIY

Part number: 12427840580
Part diagram: http://www.realoem.com/bmw/enUS/show...06#12427840580

Tools needed:
Jack
Jack stands
socket wrench
8mm socket
16mm socket
13mm socket
13mm wrench

Get the car up on jack stands and begin taking off the thick metal plate surrounding/attached to the front central jacking point. There are x7 16mm bolts (don't forget the one in the middle of the central jacking point!) and x3 8mm screws that connect to the transmission shield.

Once the metal plate is off, you can access the ground cable. It is located by the driver side header-to-xpipe connection. One side of the cable is attached by a 13mm bolt, and the other side of the cable is attached to a stud with a 13mm nut. The 13mm nut can be taken off with a standard 1/4in drive socket wrench with room to spare (so a 3/8in drive would probably also fit), but for the 13mm bolt, there is not enough room so you will have to use a 13mm wrench.

Put your new cable in and reverse all steps. Make sure you note that the cable has a different style "plate" on each end. The totally flat side goes with the bolt, and the "folded" side goes on the stud with the nut.


.
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      11-30-2017, 01:13 AM   #2
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Thanks. What problems/symptoms were you seeing?
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      11-30-2017, 07:16 AM   #3
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Quote:
Originally Posted by Redd View Post
Thanks. What problems/symptoms were you seeing?
I've been having issues where randomly the car won't even try to start. Electronics come on fine, but the starter is just silent, no struggling or anything. Then after I press the start button like 10 times it just jumps to life no problem.

I replaced the battery first, since it was 8 years old, but that did not fix it. So I saw another thread mentioning the ground cable and figured I'd try it. It's only about $40 so might as well. The starting problem would only happen about once in every 8 starts, so I won't know for sure until a few days out, but fingers crossed.

If this doesn't work, next up would be either the starter cable going to the positive signal from the battery, or the cable between the alternator and starter, or both. Following that I would finally try replacing the starter. I didn't start with that because there are a handful of threads where people replaced the starter and it didn't fix anything (same with the battery, so shame on me for not reading first ).
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      11-30-2017, 10:04 AM   #4
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Your ground strap looks to be perfectly fine and isn't the problem.

I think it's time for a starter.

I went through the same issue.


Get to the starter and I think you'll find the ground strap from the solenoid to the motor will be loose. In my case, the resistance created enough heat after enough attempts to actually create contact and the starter would crank.

Replaced the starter and all has been well since.
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      11-30-2017, 01:58 PM   #5
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Quote:
Originally Posted by doogee View Post
Your ground strap looks to be perfectly fine and isn't the problem.

I think it's time for a starter.

I went through the same issue.


Get to the starter and I think you'll find the ground strap from the solenoid to the motor will be loose. In my case, the resistance created enough heat after enough attempts to actually create contact and the starter would crank.

Replaced the starter and all has been well since.
Thanks for the tip. So would it not be possible to just replace the solenoid ground strap? Or is that an integrated part of the starter?
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      11-30-2017, 02:01 PM   #6
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Quote:
Originally Posted by M3MPH1S View Post
Thanks for the tip. So would it not be possible to just replace the solenoid ground strap? Or is that an integrated part of the starter?
I thought the same thing.

I tightened down the nut and a few days later it was loose again. Very strange. Tried loctite and same thing.

There was clearly so much resistance in the motor that it was getting this connection really hot.
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      11-30-2017, 02:03 PM   #7
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Quote:
Originally Posted by doogee View Post
I thought the same thing.

I tightened down the nut and a few days later it was loose again. Very strange. Tried loctite and same thing.

There was clearly so much resistance in the motor that it was getting this connection really hot.
Well damn, can't ever be that easy right?
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      11-30-2017, 02:06 PM   #8
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Quote:
Originally Posted by M3MPH1S View Post
Well damn, can't ever be that easy right?
I had my damn manifold on and off for weeks trying to diagnose this!

Try tightening down that connection and maybe you'll get lucky!
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      11-30-2017, 02:07 PM   #9
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Quote:
Originally Posted by doogee View Post
I had my damn manifold on and off for weeks trying to diagnose this!

Try tightening down that connection and maybe you'll get lucky!
I'll try it out, thanks a lot for all the info!
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      12-11-2017, 10:15 PM   #10
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Quote:
Originally Posted by doogee View Post
Your ground strap looks to be perfectly fine and isn't the problem.

I think it's time for a starter.

I went through the same issue.


Get to the starter and I think you'll find the ground strap from the solenoid to the motor will be loose. In my case, the resistance created enough heat after enough attempts to actually create contact and the starter would crank.

Replaced the starter and all has been well since.
That cable sits right next to the driver side header and is exposed to elements. Enough heat cycles and wet weather and corrosion/fatigue from a vibrating engine will degrade these.

Here is mine at 110k, fell apart in my hands when I removed it.
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      12-12-2017, 11:57 AM   #11
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Quote:
Originally Posted by ec_E92 View Post
That cable sits right next to the driver side header and is exposed to elements. Enough heat cycles and wet weather and corrosion/fatigue from a vibrating engine will degrade these.

Here is mine at 110k, fell apart in my hands when I removed it.
For sure!

Mine was the same way but did not solve my starting issue.

BMW is too cheap to insulate these wires like they used to.
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      12-14-2017, 09:15 AM   #12
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Just an update, changing the cable seems to have helped very slightly, but it did not fix my issue. I went ahead and ordered a new starter, and hopefully that fixes it.
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      12-14-2017, 10:08 AM   #13
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Quote:
Originally Posted by M3MPH1S View Post
Just an update, changing the cable seems to have helped very slightly, but it did not fix my issue. I went ahead and ordered a new starter, and hopefully that fixes it.
If it is your starter that is going bad it makes sense you'd see a marginal increase with a new ground strap as it would prove less electrical resistance to the starter.

Good luck, not a very hard job but still a PITA!
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      12-14-2017, 10:10 AM   #14
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Quote:
Originally Posted by ec_E92 View Post
Quote:
Originally Posted by M3MPH1S View Post
Just an update, changing the cable seems to have helped very slightly, but it did not fix my issue. I went ahead and ordered a new starter, and hopefully that fixes it.
If it is your starter that is going bad it makes sense you'd see a marginal increase with a new ground strap as it would prove less electrical resistance to the starter.

Good luck, not a very hard job but still a PITA!
Yeah the actual replacement of the starter looks quite simple, it's just getting to the starter that will be a pita
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      12-14-2017, 10:34 AM   #15
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At 90k miles, the engine ground strap on my winter driven 08M3 is no longer shiny but is intact. I have treated it with deoxit and protectant. My exhaust grounds broke a couple of years ago and I made new ones.
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      12-14-2017, 10:52 PM   #16
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Quote:
Originally Posted by pbonsalb View Post
At 90k miles, the engine ground strap on my winter driven 08M3 is no longer shiny but is intact. I have treated it with deoxit and protectant. My exhaust grounds broke a couple of years ago and I made new ones.
For $40 it might be worth it to just replace it proactively so you don't get stranded. I was lucky mine failed on my morning commute in my neighborhood (car just died on me while driving and would not restart). I was able to walk back home and get another car without too much delay to my day.
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      12-15-2017, 08:53 AM   #17
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I have a lift and am under the car every month or two. As soon as I see a sign it is disintegrating I will replace it. Iíll be under there this weekend and will check it again.

It may be that people who drove with failing motor mounts prematurely stressed their cables. Or maybe people with the stock x pipe are putting more heat into that area due to the cats.
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      12-15-2017, 11:25 AM   #18
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I replaced my starter last year, pretty much the same symptoms you had. Tried the ground strap and it didn't do anything.

Made a thread about DIYing the starter. Not a bad DIY, just make sure you have flex sockets and the correct sizes.

I also sat on top of the engine to get to the bolts behind the engine. IDK why people were complaining it was hard to get to, but there is plenty space.
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