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Discussion Starter · #1 ·
Hey all
I've got an 06 550i that has been slow turning over for about a year and a half now. Bought it like that. Salesman states he had put a new battery in and still had the problem.
I go to swap for a new battery finally and come to find out this brand new Interstate battery has a collapsed cell.
I throw a duralast h8 in and it starts stronger but not anything like my 7 series.
I am wondering if it could be a bad ground from starter?
I am afraid there is something wrong with electrical system that may cause the cells in the battery to foul like what happened to the Interstate.
Thanks for any help on this.
 

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I am afraid there is something wrong with electrical system that may cause the cells in the battery to foul like what happened to the Interstate.
Very unlikely.

- It could be a bad connection anywhere in the loop. That includes positive and negative battery cables and the ground connections to the chassis. This is the most likely scenario.
Check all connections. If no luck, capture voltage waveform with an oscilloscope on ground and supply when starting the car and trace back to the faulty part.

- Could be high resistance of the engine or something on the belts.
Is it the same when cold or warm? Measure current draw of the starter.

- weak battery, well you just got a new one.

- Or a bad starter.
If all the above is good, just replace starter.
 

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Discussion Starter · #3 ·
Very unlikely.

- It could be a bad connection anywhere in the loop. That includes positive and negative battery cables and the ground connections to the chassis. This is the most likely scenario.

Check all connections. If no luck, capture voltage waveform with an oscilloscope on ground and supply when starting the car and trace back to the faulty part.

- Could be high resistance of the engine or something on the belts.

Is it the same when cold or warm? Measure current draw of the starter.

- weak battery, well you just got a new one.

- Or a bad starter.

If all the above is good, just replace starter.
Thanks for the info, I will most definitely start here as I've already got her apart. Im waiting on the Carly to check for soft throws, though.
Do you have any insight on how intensive it is to trace the loop, or what it may require?

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Thanks for the info, I will most definitely start here as I've already got her apart. Im waiting on the Carly to check for soft throws, though.
Do you have any insight on how intensive it is to trace the loop, or what it may require?

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I have the same car, so I can take pictures of the location but might take a day or two.

I don't expect this issue will show up on a diag software. Maybe the DME has some information since it measures the voltage dip when starting.
 

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Some starters on the I6's are known to weaken and fail over time; probably solenoid. Usually starter has to crank progressively longer to start. I don't know if the same applies to the 8's.
 

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Discussion Starter · #6 ·
I have the same car, so I can take pictures of the location but might take a day or two.

I don't expect this issue will show up on a diag software. Maybe the DME has some information since it measures the voltage dip when starting.
Thank you. Pictures would be much appreciated.

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I'm new here, and just recently bought a 2001 Z3 with a similar problem. I have started cleaning cable connections throughout. On just the positive cable from the battery to the starter I've found 7 connections. Open them all up. That is the battery clamp, the in line fuse block, and the jumper connection under the hood, and the starter connection. Clean, sand, scrape until everything is shiny. When re connecting, use some di-electric grease to keep out moisture. If you want to be anal, like me, a 40 year sheet metal worker, and you want to make it so it won't corrode again, get some rosin core solder, and using a soldering iron, cover all the copper connecting surfaces before reassembly with solder. Copper oxidizes and corrodes. Lead-tin solder does not, and is soft enough to be malleable and squeeze together to make a good connection I have used this practice on a brass buss bar in my boat which never leaves the water because there is no trailer, and is constantly in cold damp conditions. Connections I made 18 years ago have never needed another minute of my attention since. I won't know how well this works for a few days because I'm also working on doors with airbags removed, and can't install the battery until the airbag is back in. I will return and let you know if it solved my slow start problem.
Keep the faith
Fix it once well
gmybeer
 

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Discussion Starter · #8 ·
I'm new here, and just recently bought a 2001 Z3 with a similar problem. I have started cleaning cable connections throughout. On just the positive cable from the battery to the starter I've found 7 connections. Open them all up. That is the battery clamp, the in line fuse block, and the jumper connection under the hood, and the starter connection. Clean, sand, scrape until everything is shiny. When re connecting, use some di-electric grease to keep out moisture. If you want to be anal, like me, a 40 year sheet metal worker, and you want to make it so it won't corrode again, get some rosin core solder, and using a soldering iron, cover all the copper connecting surfaces before reassembly with solder. Copper oxidizes and corrodes. Lead-tin solder does not, and is soft enough to be malleable and squeeze together to make a good connection I have used this practice on a brass buss bar in my boat which never leaves the water because there is no trailer, and is constantly in cold damp conditions. Connections I made 18 years ago have never needed another minute of my attention since. I won't know how well this works for a few days because I'm also working on doors with airbags removed, and can't install the battery until the airbag is back in. I will return and let you know if it solved my slow start problem.

Keep the faith

Fix it once well

gmybeer
Wow that is a great idea, why haven't I ever thought of that?? I'm a union fitter so I've got plenty of solder laying around, that's for sure.
Please post back when you get your car up and running and let us know if a bad connection was the issue!

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