Yesterday while getting ready to mow, the tractor suddenly stalled. I got it run but it stalled again. The same happened a couple more times. A friend helped me troubleshooting the problem and he said the fuel filter was really dirty, so we removed the filter reservoir and drained it. There were little brown particles/spots on the filter. The filter reservoir was automatically filled as soon as we screwed it back on. After a few tries, I got the tractor running again but then suddenly it stalled. This time I noticed a short puff of white smoke coming out on the right side of the engine. The PTO was not on during all this time. Today I installed a new fuel filter but the tractor would not run. I bled the fuel line as outlined in the operator's manual: opened the air vent cock while cranking the starter for 20-30 seconds, then closed the air vent cock just before I stopped cranking. I repeated this bleeding procedure 3 more times but no luck. Engine turned over good but would not run. I will do the injector line bleed this weekend, following the video posted in this forum. In the mean time can you tell me or guess what caused that puff of white smoke and where it might come from. What is fuel solenoid, as it was discussed in one post. BTW the tank was almost full. I would appreciate very much any recommendations that you might have.