Cam timing on 1.9 diesel renault traffic x reg?

hi, a friend of mine has recently changed the cam seal on his reanult traffic 1.9 diesel engine and has messed the timing up. i offered to have a look for him as i know a bit more than he does. he tells me the sprocket to camshaft isnt keyed in anyway so it could go on anyway and it hasnt been put back on right so the timing mark is now wrong to how the followers are acting, can any1 help in setting the cam up?ive set the pump and crank timing as they should be and taken the rocker cover off so i could see where the followers were at but cant seem to get it right so the pistons dont catch the valves. my autodata software says cam timing is BTDC, wot does this mean. Cany anyone help as this is frying my brain? many thanks