You don't know it but this forum helped me get my truck running again. I did not ask any questions for they had already been ask. I changed the fuel filters in my 2009 f250 6.4l and I still don't understand how air entered the system because I followed the procedure exactly. I read the post replies and after about 5 hours of work was able to get the air purged out. I would like to thank all for replying to the post because they saved me a trip to the dealer and no telling how much money.