93 D250-Had a shudder so bad that tailpipe struck corner of aux tank. Fixed the shudder TSP and idle too slow. Now the Aux tank will not fill seems like it's plugged. I blew the air relief and filled the tank Ok once then it started all over again. I am going to call Transfer Flow Co in Chico CA it's their tank about 9 - 10 years since installation by previous owner. The fuel that's in the tank can be used and the switch "Aux-Main" works ok. any experience? Suggestions?Oo. 
