Primastar Van (Traffic) Cutting out?

Have a 53 primastar 1.9dci, same as a renault. Have had a new engine installed 6 weeks ago along with timing gear, erg valve air flow sensor and all filters. Now the van keeps cutting out, and i have difficulty restarting it, and when it starts it sounds like a fuel problem, but once started it runs great. The problem is it cuts out if i go over a bump,so i checked for a loose connection every thing looks tight, so with the van running i shut the bonnet and the van cut out, strange i know, got the van running again and hit the top where the bonnet lock is on the left hand side and every time i do this it cuts out, so am woundering if there is some sort of sensor round there that cuts the power in case if a collision.....any help would be gratefull.