Gmc Diesel things to check for

Hi All, I was using my 2500 in the yard today and all of a sudden it died for no apparent reason. I know with gas engines you check for spark and fuel but I find myself new to the diesel engines. Any suggestions would be appreciated. Thank you

Hi All, I was using my 2500 in the yard today and all of a sudden it died for no apparent reason. I know with gas engines you check for spark and fuel but I find myself new to the diesel engines. Any suggestions would be appreciated. Thank you
What year?

Diesel engines are fuel controlled and compression fired.
Some information about the year and mileage would help.
When was the last time you changed the fuel filter?

it's a 1991 3/4 ton with 61k. It was a former fire dept vehicle (meaning it was town maintained and sat a lot) that only used to plow the fire dept parking lots. I believe I noticed a slight leak in the fuel line which would certainly make sense but I just couldn't believe it died all of a sudden. I am now told after I repair the line I will need to bleed the fuel line. Is this true and if so I'll take any suggestions. Thank you