td5 cuts out when drivng

hey guys need help. just had car in for mot and i had fuel leak so they changed fuel pressure regulator. drove away from garage fine went to work but drivin the 2 mile home the landy cut out 3 times. when it turns over it struggles and then dies out. i had to bump it to get it running twice on the last time it managed to start but makes a clicking noise but does not sound the same as when the starter clicks. also when it did start the car was engulfed in white smoke.

does any one have any ideas to what this is.

thanks