engine fires, revs quickly on its own then shuts off

[Vegified TDi]

Hi folks. Started 2001 Golf tdi up this morning and drove for about 5 minutes. Parked it for 15 minutes. I tried to start it. It turned over normally, fired normally, but then the engine reved up quickly to 2500-3000 then immediately shut off. I tried this 10 times with same outcome.

Also there was a "clunk" sound from the engine on a few of the attempts. Timing belt looks normal.

Sound familiar to anyone?

Thanks
Torie