my mate[an old school mechanic] bought a cat d S/R 1998 e300td, that wasn't running [no key]he traced previous owner, got her to get new key from MB Blackburn and all was working fine. Leaves it for three weeks or so, then won't start, so charges battery, turns over but still won't start, a bit low on diesel so he puts 10L in, still won't start but is turning over, he is getting fuel to the pump he has checked, but is stumped as to what could be the problem. Could the immobiliser have kicked in when battery flat or something? anything else? what else can he check or do?