How much air can there be in injection pump?

[i-osprey]

I have a 1981 300D that is having some air in the fuel lines/injector pump issues.

I ran out of diesel about a week ago and ever since I have been having a very rough running engine.

I bled the injector lines for a while with no results. I had the engine running and I loosened one line at a time.

I then found a leaking fuel line before the plastic fuel filter. I fixed this problem and there is little to no air in that filter now.

I then tried to bleed the injector lines again today. I loosened the nut that holds the injector line to the injector on the front two injectors and nothing but foamy air comes out.

I left them off for almost ten minutes with me increasing RPMs occasionally but they still put out foamy air. Not much diesel at all.

I then loosened one of the back three injector lines and there was a noticeable drop in engine performance.

I think I am running on three cylinders and I don't know how much air the injector pump can have in it. Could I have an air leak somewhere else that only affects the front two injector lines?

Is there something else wrong?

Also, to add insult to injury I cross-threaded the nut on the front injector line and now I presume I need a new line altogether. Anybody have one for sale?