I have a '92 240 that won't start. The engine will turn over but won't catch; all the fuses appear to be intact, and I have even replaced the fuses relating to the fuel injectors and fuel pump (last time it wouldn't start, the fuses were the problem). On the off chance that somebody siphoned out all my gasoline, I got a can and put a gallon in it, but it still won't catch at all. Not even a sputter.
I'm trying to sell it, and it's been sitting in a lot behind my office for the past few months. I start it and drive it pretty much every week; on New year's Eve, I ran it for more than twenty minutes, and it idled as smoothly as my new Honda. Not the slightest problem starting it up; three days later, I couldn't even get a cough.
Can anybody give me an idea of what I might check or do to fix this? Like I said, I'm trying to sell it and have been trying for a few months, so if I have to put a bunch of money into it, my wife is going to kill me. HELP! Thanks!

-UNCJD2003