John, I would suggest in changing out your fuel filters before starting engine. Motorhome
has been sitting for a long time, what will happen any water, dirt etc. that was being carried
in the fuel while engine was running will settle to bottom of your fuel filters ( with engine
being stopped long period ). I would drain primary fuel filter on bottom if equipped with fuel
drain plug, and change out the secondary 2 micron 1R-0751 fuel filter. In some cases after
engine has been started such as in your case sitting idle, foreign dirt in fuel rail on engine
will plug orifice on fuel pressure regulator on engine. Dave Atherton Retired Cat Mechanic