Volvo: intermittent trouble with starting, mass air flow sensor, mass air flow

Question
Hi,
Recently purchased a 99 S80 and it won't start at times.  We used the dealership "service" and they stated that they put in a new Mass Air Flow
sensor.  About two weeks after this "service" is when the trouble started.  Our normal mechanic has checked many things, but can you give us a few things that he can check out.  He did check to see what the computer said but it had no message.  So we would appreciate any help.
Thank you

Answer
Nancy,
Engine cranks and will not start, how about a fuel pump or the relay starting to fail. They will not leave codes in the system. Is the charging system working and battery good? Voltage may be low, and not enought power to the starter or control units. Is the neutral switch ok? Perhaps the starter interlock system assocated with with the chip in the key is failing. Usually the antenna ring around the key is at fault.