Runaway diesel
I need advice on resolving issues following a runaway diesel engine on a 2006 Zafira 1.7 CDTI. The circumstances were that I was driving along normally, then plumes of thick white smoke came from the exhaust. I dipped the clutch, but the engine raced even higher. I coasted to a halt and turned off the ignition, but the engine continued to run, until eventually it stopped of its own accord, before self-destructing. The garage recovered it and said it could have been caused by an attempted regeneration following a blocked DPF.
So far, they have done an oil and filter change, emptied out all the induction components of the engine oil/diesel fuel mixture, and checked the timing belt, timing and camshaft sensor, but the engine will not fire up. They have found multiple error codes relating to overrevving. They tried Easy Start, just to see if they could get it to run, but it refused to start. There are no nasty noises when it turns over and it appears to have good compression. It feels normal on cranking. The injectors cannot be removed for a test. Eddy Hurst One of the more common problems with the 1.7 CDTI engine is a failure of the turbo seals, which allows engine oil to enter the inlet system. Once in the cylinders, the oil will begin to burn and can feed the engine, causing the runaway effect you have experienced. This is far more likely than a failed regeneration being the cause.
You mention that the induction components were emptied of oil (there should be no fuel in the induction components) and this would back up the idea that the turbo was the cause of the failure. The multiple codes found should be cleared to allow any further returning codes to show up.
You say that the engine stopped of its own accord, before self-destructing. If this is the case, any damage to the pistons, bores or valves may also have damaged the injectors. It would be interesting to know how much oil was left in the engine when it finally stopped. A very low level would confirm that the engine was running on engine oil when the failure happened, but if the level was still high then the failure may have been due to a fuel injection fault.
As the engine will not fire up with Easy Start, this suggests that there is insufficient compression. The next step would be to remove the injectors to test the compression of the cylinders and to check the injectors for damage.