Caddy 2.0 SDI: Starting Problems & Troubleshooting

Hello,
My friend's Caddy 2.0 SDI with the BDJ engine sometimes fails to start when it's cold. It only starts after a very long cranking period, and then it suddenly starts and runs smoothly and normally. The longer it has been standing and the colder it is outside, the more frequently the problem occurs. This only happens when the engine is cold and at irregular intervals. In short, it either starts perfectly or not at all.
Error memory is empty.
The idle speed control system shows completely normal values.
Battery recently replaced.
Starter motor replaced.
Twin-pump, 30,000 km old (over 3.5 bar at 1500 rpm and 11 bar at 4000 rpm).
PD cable harness, 10,000 km, old.

Thank you in advance for any further tips and ideas.

Hello,

Please check if the vehicle does not start whether the engine control unit is accessible via diagnostics.
If it is not powered, no diagnosis can be performed.

Best regards, Rainer.

Yes, he is reachable.

Hi.

3bAFN wrote:

Yes, it is reachable.

Even if the vehicle isn't starting, does the ignition key simply stay in the "on" position when you release it?

3bAFN wrote:

he comes suddenly and immediately starts walking very calmly

This actually argues against problems like air leaks in the injection system/common rail, because in that case, the engine would initially sputter, and it's rare for all four injector elements to fill evenly at the same time.

Have you checked the coolant temperature in the engine control unit during a cold start? Please pay attention to whether the glow plug/preheating light in the instrument cluster briefly illuminates when the ignition is turned "on" (which is normal) or remains off if the subsequent start attempt is unsuccessful.

Best regards, Rainer.

Yes, even then, the control unit is accessible.

The coolant temperature sensor is providing realistic values. A test with the cable disconnected did not improve the situation. In this case, the displayed coolant temperature was (I'm not entirely sure about this) 12.4 °C.

The glow plug illuminates normally for a short time.