1984 GMC Jimmy 6.2

I bought it 2 weeks ago and it has been sitting for that time, and now there is no fuel to the injectors. Cracked injector #one and cranked for a while. no fuel. I want to pull the return line on the injector pump and add compressed air, but how many PSI? And I think I know which is the return but do I inject into the hose or the fitting? So many different ways outlined online.

I know nothing about the 6.2. Is there a owners manual you would recommend for the 1984 6.2?

My 7.3IDI (1992 ford centurion) ran out of fuel and I cracked an injector and it started in about 15 seconds. I like my 7.3 so much I wanted an older gmc diesel jimmy as a rock crawler project.

New jimmy needs love and I have lots to learn. Thank you for the help.

 

IP fuel return is the line at the frt of the IP-no more than 5 psi in that line with the fuel cap OFF of the tank.
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Might be that the mechanical lift pump has given up the ghost and a leak exists in the fuel system allowing air to get in?