[SVKDK]

Hi,

I'm having issues with a 2007 V6 TDI. The car is originally equipped with two batteries.

The car drove just fine, was parked for ~8 hours in cold weather and could subsequently not start. It cranked but didn't start. Several attempts to boost using starter cables from an Toyota RAV4 + an additional battery didn't solve the problem. Car was flatbedded to the mechanic.

The car was charged with both batteries mounted using the posts under the bonnet. VCDS showed a hell a lot of errors due to low voltage. After clearing these (several attempts) they've all disappeared.

The car seems to crank just fine but just doesn't start. Thinks that have been checked:
1. Belt to high pressure fuel pump intact and spins when cranking.
2. Engine RPM (G28-sensor) shows between 147-168 rpm when cranking.
3. Rail pressure is dead zero (0) when cranking.

Especially regarding
2): Could anyone confirm whether there's a lower limit of engine crank speed before the ECU initiates a start?
I found the following on another site:
V6 TDI battling to start in the morning - 4x4 Community Forum
The cranking speed needs to be at least 280rpm on the v6 TDI

3): Is it correct pressure should first be built after sufficient RPM has been reached? Is there some kind of magnetic clutch on the pump?

Any input would be very much appreciated.

 

[MJHandy]

Have you confirmed fuel flow while cranking?

My first thought was just cold weather, but not if it's in a mechanics bay. Unless it's outside and it's still rather cold.

 

[SVKDK]

No. Would I be able to do so via VCDS?

I also initially guessed it was due to the cold weather but the car has been in the mechanics garage for 24+ hours in approx +18 degrees celsius.

 

[MJHandy]

On these engines I'm not 100% sure. My old jetta I'd crack an injector and have someone crank.

Does the vcds give any codes?

 

[SVKDK]

No codes at all for the engine.
I've seen others mention having a code for eg. "low fuel pressure". I would expect that would be the case if it was fuel starvation?
The Webasto heater runs just fine but I'm guessing it has separate piping directly to the fuel tank.

 

[SVKDK]

And there's no smoke coming from the exhaust. One should think there would be some smoke/smell if diesel were injected.

 

[SVKDK]

Update: The mechanic checked again this morning - no codes at all. He then subsequently retried starting it and after 2-3 attempts it started (!)
The car has now been picked up and is apparently working as normal.

 

[MJHandy]

Glad to hear it's started.

I wonder if the battery was the issue. Not enough juice to crank fully when she's cold.

 

[SVKDK]

Could be. I'm guessing time will tell. We still have the coldest months of winter to come.