Hi 

I’m hoping someone may have heard of issue like this and will be able to help:) 

My car is 2009 superb 3.6 DSG 4x4

 

I’ve been experiencing weird starting issue on my 3.6 superb - as I’m turning key to start a car it won’t start until I release the key. So starter motor will go on as long as I’m holding a key and will not start a car until I release it. When it gets warmed up it starts as normal

 

 

It happened last year for first time for about a week and went back to normal

 

Then this year in March problem returned but after few weeks of starting when key is released it decided not to start at all. I’ve checked all possible fuses fuel pump checked if fuel gets to the engine - all fine. Check for faults with VCDS - none. After 2 hours of trying to find an issue battery died. We tried start it from jump leads and it worked as normal. 

 

Back then I thought it could be quality of fuel because I’ve used cheap petrol station as I couldn’t find anything better. So I’ve started using only shell v power from then. 

 

It went back to normal for few days and started playing up again but it was still starting.

 

One night releasing key didn’t help so I’ve used booster/power bank and it helped. About week after it didn’t start at all - with or without booster. 

 

I had it towed to garage where they’ve: 

Checked engine sensors 

Tried with other battery 

Replaced ECU

Checked earth points 

Checked power consumption when stationary

Replaced stater motor 

Checked battery and alternator 

Checked for faults again 

Checked coils 

He reckons there is very weak spark in engine (new spark plugs about 6 months ago) 

 

(Luckily he managed to return ECU and starter motor)

 

So after three weeks in garage my old ECU came back he plugged it back in charged battery and started it up from booster. Mechanic said he ran out of ideas. So I’ve got car back which starts for now. First days it started as normal now it’s back to release key starting. 

 

Things I’ve replaced on car recently (maybe something helps)

New Bosch s5 battery 

Spark plugs 

All filters 

Timing chain 

Basically whole engine resealed 

Dsg oil 

 

Sorry for this chaotic post - I’ve tried give as much info as possible. I wanted to get rid of it but we buy any car offers only £2.200. I’d rather to keep it as it gives me a lot of joy. 

  

Thank you for help

7 hours ago, Kamilsgru said:

Checked coils 

He reckons there is very weak spark in engine (new spark plugs about 6 months ago)

What's the LT feed to the coilpacks like?

I don’t know to be fair, how can I check it ?

1 hour ago, Kamilsgru said:

I don’t know to be fair, how can I check it ?

I don't know for sure either. I'm taking your (and your mechanic's) word for it that the coilpacks and plugs are all good. Given those being good, the most likely cause of a weak spark is a low voltage (or high resistance) in the LT feed, which really requires a multimeter to check.

That why he tried replacing starter motor as he thought it may have too high power consumption during start, but after that he gave up.

 

But on other side engine runs spot on, there is no misfires or any other issues. 
 

Looks like I need more of magician than mechanic lol

7 minutes ago, Kamilsgru said:

Looks like I need more of electrician than mechanic

Edit inline, bold.

When you turn the key to Ignition On you liven up Terminal 15 which activated the ECU & sparks.

 

Just wondering if you might have a faulty ignition switch.

 

Possibly when you turn the key to the Start position you are loosing Terminal 15 voltage, so no sparks.

Then when the key is released the engine is still turning & terminal 15 is restored.

 

Suggest you connect a test meter to terminal 15 & watch it while trying to start, it should be live all the time.

 

Just a thought & not any previous experience of this.

Thank you for reply 

do you know where I can locate it ? 
 

Here is the diagram for the ignition switch. 

 

I've taken a photo as I don't know how I can copy a PDF diagram onto here.

 

Diagram of Terminal 15 relay in the post below as too large to add on this post.

Thank you very much for that. 
I will try tomorrow morning 

it did start as normal yesterday morning but in evening didn’t start. I’ve managed to start it up with booster.