Plowing my garden tractor started to run rough, black smoke, low power. I drained diesel, changed fuel and air filter, now does not start. I followed instructions on video, bled all the lines, made sure fuel is going from tank to injector, only small amount comes out of injector when the nut is loosened. Still will not start, tries to turn over for about 3 seconds. What else can I do? Only 102 hours on this tractor.