2.0L BKD - difficult to start hot

[mechanic]

Bought an 08 TDi Golf a few months ago. After I bought it I found it would crank for 10 seconds before starting, or not start at all when hot! Tested the battery under crank and found it dropping to 9.5V. Replaced battery with Varta original.

Now, it starts almost instantly when cold, but seems to crank for 3 or 4 seconds when hot and starts with a jerk. It's never let me down since the new battery, but it still isn't quite right.

It drives and operates flawlessy otherwise - a great car.


Has anyone else had this problem and/or solution?

[stickshift3000]

Hot start issues are fairly common with the bkd engine.

have you had it scanned for any fault codes?

[mechanic]

yeah, it's the first thing I did. No fault codes.

[Umai Naa!!]

What's the state of the intake flap and EGR valve like?

[mechanic]

intake flap operates normally, and there are no EGR DTCs. I'm pretty sure the EGR would log a DTC if it didn't operate normally.
Intake manifold inner walls are thinly covered with the normal carbon buildup.

I've read on other forums (USA) that the starter motors wear internally and this reduces the cranking speed. The engine code is different over there. Is this starter fault a problem in Australia too?

[mechanic]

intake flap operates normally, and there are no EGR DTCs. I'm pretty sure the EGR would log a DTC if it didn't operate normally.
Intake manifold inner walls are thinly covered with the normal carbon buildup.

I've read on other forums (USA) that the starter motors wear internally and this reduces the cranking speed. The engine code is different over there. Is this starter fault a problem in Australia too?

[Umai Naa!!]

There are starter motor-related issues, as well.

Basically, the injectors won't inject if the starter motor can't turn the engine any faster than 280rpm.

[poyta]

Are you waiting at least a 2-3 seconds for the glow plugs to warm up before turning the key?

[mechanic]

Yep, tried combinations of not waiting for glow plugs, waiting until lights extinguish, and reheating 2 or 3 times before cranking. It doesn't seem to make a difference to the hot start problem.
In any case, it only happens when the engine is at operating temperature. This fault can occur literally seconds after I switch it off after a good drive.
I could understand if it struggled to start when cold, but this goes against everything i've ever learned. The battery should be slightly above normal charge and cylinder compression will be at its highest. If it also struggled to start when cold, I would have a better chance of finding the problem... but I'm stumped!

280RPM huh? Do you have any more info on this?

[Umai Naa!!]

If you have a way of measuring the cranking speed, you'll be able to confirm this.

Basically, the technical bulletin went on to say; if the battery is good, but the cranking speed is less than 280rpm, replace the starter motor.