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C6 2.7 hdi struggles to start
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bigbruggsy   
Sat Jun 07 2025, 05:14pm
Joined: Mar 26 2018
Member No: #3483
Location: Beziers
 Hi all, It's been a few years since I've had a C6. But yesterday I picked up a C6 from the auctions here in France. This new to me C6 seems to have an issue with starting, well it's a weird one. I'll describe it first and hopefully it will make sense to the smarter ones here on this group.

When i went to collect the car the motor would turn over slowly and therefore not start. They brought round a car and jump started it from the front terminals. No problem, she started started first go. So I thought low battery. No issue, I had 600klms to drive home.

I needed diesel though, so I went to the first service station. Filled her up and again, the motor turned over slowly, but she started (no jump start, just using it's own battery)

Then an hour later. I had to stop (the car did a Regen and smoke inside the cabin, another issue) But I couldn't start the car again, battery was dead it seemed. the car even said it had low battery power.

I got a jump start from a battery booster pack (tow truck driver) again connected to the front terminals. No issue. Started easily first go.

So I thought, this battery isnt holding charge, so i went to a battery store. They tested the battery and they said it was ok. I showed them what happens when I start the car and they said ok, maybe it is a bad battery. So we put a new one in, same issue with slow motor turning over, but it did start, with some difficulty though. But we figured after a few hours of driving it would be charged enough. But sadly no. Now I'm home after a 400klm or more drive and the new battery still struggles to to turn the motor over easily. It does start, but it sometimes sounds like it will not.

So my question after such a long description is, could there be a connection between the new battery and the starter motor that is causing a loss of amps? As the car starts easily using the front terminals?

The batteries I have used in the back of the car are of the correct amps. Actually I found a recent receipt from the previous owner for the battery that was in the car, it was only 2 months old! So obviously a previous issue.

Thanks again for the help! It's so good to have a C6 again
MGmike   
Sun Jun 08 2025, 09:15am

Joined: May 21 2017
Member No: #3151
Location: South Queensferry
 That all sounds typical of a failing starter motor.

Without getting in to the technical details, there will be a drop in voltage at the starter motor when power is coming from the battery in the rear as compared to one attached to the jump connection under the bonnet. The "extra" voltage (and current) from the jump is enough to make the starter motor spin that tiny bit faster to get the engine started.

Change the starter for a good quality replacement and I'll bet all will be well.

Oh, and back
bigbruggsy   
Mon Jun 09 2025, 05:22am
Joined: Mar 26 2018
Member No: #3483
Location: Beziers
 Thanks MGmike. Is there a way to test the starter motor while on the car? Or is it almost a certainty its the issue? Good quality replacement, do you have any suggestions? Thanks again.
bigbruggsy   
Mon Jun 09 2025, 06:08am
Joined: Mar 26 2018
Member No: #3483
Location: Beziers
 I've had a good read of some instructions on how to remove and replace the starter motor and it looks like a job I can do (I have the time) Does anyone have suggestions for which brand of starter motor I should buy? I prefer to do this once (so will buy new). Thanks again.
Wesa   
Mon Jun 09 2025, 04:02pm
Joined: Nov 02 2024
Member No: #5684
Location: Järvenpää
 Not sure if the new starter is always required? I had a similar challenge with 2006 2,7 hdi (305000 km). I removed the starter, by the idea that better check it before buying a new one.

Inside it looked fine, some carbon dust there was (like in a typical hyd pump motor), but the brushes were fine and the commutator just ran-in. I cleaned carbon dust off and well lubricated the bearings, also inside epicyclic gear. The cable terminals were oxidised and cleaned, those also. Also, all other big connections were cleaned the same time. In engine bay and rear.

After reassembling all, it ran like a new one. And do still after 10 tkm.
Not sure which one finally was a main root cause, but the combination helped!
bigbruggsy   
Tue Jun 10 2025, 07:03am
Joined: Mar 26 2018
Member No: #3483
Location: Beziers
 Does anyone have any experience with Henkel parts? They have this lower cost option. I just wonder about the quality.

Henkel Parts Starter
12V, 2.2kW, Number of teeth: 21
Ref.: 3115777
Nominal power [kW]: 2.2
Voltage [V]: 12
Number of mounting holes: 3
Quality: Standard Neuteil
Item number: 3115777

Our price: €186.48
EAN number: 4063214183507
Tjensen   
Tue Jun 10 2025, 09:41am

Joined: Jul 17 2012
Member No: #954
Location: Bergen
 Usual problem on the 2.7 is bearings. Changing bushes in bearings and a general inspection/cleaning/lubrication usually makes it "new"
 

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