1987 Jeep YJ Why won't my Jeep start?

Ok. I bought an 87 YJ from a friend of mine after he ran it into the back of a flatbed going down the interstate at about 65 mph. He drove the jeep onto the flatbed after the accident, and then drove it to park it at his parents house once it was towed home. It sat there for two years. I purchased it and sent it to a guy to have the body work done(which took a whole year!), So it has by now been sitting for almost four years. I have given the jeep a complete tune up, changed the head gasket, changed out a bent push rod, put on a new starter, and put on a new ignition coil. The jeep will NOT start up. It will turn over, but it just won't fire up. Any ideas? I am not a mechanic, I'm just a woman who wants to get my jeep running! It has been at a friend of mine's shop(he is a mechanic) and he cannot get it to start! He has adjusted the timing and other things, but it will not fire up. Please, if you have any idea what the problem may be. Again, it ran after it was wrecked, but not now. Please help!