Wont start. i replaced fuel assembly unit...ran for a week and now it wont start!

When you say itwon't start I'm assuming the starter is turning the engine over but it won't fire. If this is the case then you need to check to see if you have fuel pressure and then check for spark at one of your spark plug cables. If either one of these are missing car won't start. If both ar present then perform a compression test on all cylinders and checkyour readings this will help to tell you if you have any internal problems. Also if you have fuel pressure and spark check your injector circuits by unplugging an injector connector and hooking up a noid light (availeable at any auto parts stor tool section) see if it flashes while cranking engine, if it's good it'll flash rather quickly. GL