[AT] Gas problem now diesel

[jtchall at nc.rr.com]

OK, in the dark on this one. Dad's 4020 Deere is diesel. We haven't been 
adding anything to the fuel, should we? I actually did just buy some 
injector cleaner as it was skipping when idling about a month ago when he 
was harrowing some corn land. The cleaner seemed to resolve that issue. 
We've noticed some pretty nasty stuff in the fuel filters lately, been 
thinking of adding a filter on the supply tank.

John Hall