Ford Fiesta TDCi starts and stall immediately

I have a problem with my Ford fiesta tdci 2006 model. I was driving one day and stopped in town for an hour or so.Then started the car and it started hesitate even on low gear. Then it would not even go past 20 kmph.The coolant temp was normal.Then all of a sudden after driving like that for a km or so then temp went very high and all the coolant leaked down.I let it cool down then started again this time the throttle wouldnt respond.The next day it would idle for 5-6 secs without any throttle response under 500 rpm and it stalled.I noticed black smoke from tailpipe. There was a leak in the fuel line so fixed it fine.Now the car will just start and stall immediately even if i depress the trhottle.No work.The OBD scanner showed no error code.The fuel pressure while i crank is 250 bar.The mechanics from dealer cleanned the EGR but no luck get it to stay running.I have no idea what to do.Please help.Thank you