I have a 92 cummins that's got me and the local Cummins guru stumped.
If I take the 3rd injector line loose it foams out of it and runs fine minus the third cylinder obviously but when I tighten it all the injectors get air and it quickly dies. Does anyone have experience with this problem?

 

possable cracked injector fuel line
There could also be a crack in a rubber fuel line before the injection pump

 

Try swapping the #3 injector to another cylinder and see if the problem goes with it.

 

If it's a cracked injector line wouldn't it spray fuel? And I tested the line to the tank by putting a hose directly into a can of diesel.
And I don't see how it could be an injector issue but I could try switching it.