Hey guys. Haven't driven my 99 7.3 in 6 months. Batteries have been kept charged. No problem there. Long crank before it will start, has a half a tank of fuel in it. Should I top it off with fresh fuel with stanadyne or run it low and fill it up and add stanadyne? Once it starts it seems to run good. Just long crank times before it starts. Drove it at low speeds for about 4 miles. Might have improved slightly but can't say for sure.

 

6 months isn't terrible, but it would have been better it the truck had been topped off and a biocide added (but you probably already know that). My truck? I'd top it off with fresh diesel and add the biocide, drain the fuel H2O separator (replace the filter if it's been awhile), and drive it. 2nd tank maybe use an injector cleaner.

 

Six months isn't going to hurt diesel fuel sitting in a truck tank, gas could be questionable at that age depending on the weather and vehicle but diesel ages much better.
It's not uncommon for farm machinery to sit for almost a year without being used and it's completely fine on the old diesel but we do like to park it with a full tank of fuel to minimize in tank moisture condensation.

 

My truck sits in a garage all winter long, and I never worry about it. I just treat the fuel (Standayne or Motor Craft) and not worry about it. Always fires right up in the spring when I need it to.

Sarge