Difficulty getting Ford 3000 to fire

[NJClark7]

I have a 1971 Ford 3000 Select-o-speed diesel with a Simms fuel pump. I serviced it with new filters, gaskets and fluids this summer and got it running well. This is my first diesel tractor. Recently, I was so enamored with tilling up my ground I didn't realize I had ran out of diesel fuel. Thinking this was like an unleaded vehicle, I filled it up with 4.5 gallons of diesel and tried to start it. To my surprise the battery will crank but the engine won't fire. There is grey diesel smoke coming out of the exhaust and the battery is healthy, cranking at 10.8 V. Now, I know I'm an idiot and should have never let the tractor run out of diesel. Air had gotten into the fuel lines. I have bled the fuel filters, attempted to bleed the Simms pump (Although diesel only comes out when the engine is cranked, not by the small hand pump), and I have bled the 3 fuel injectors where they meet the engine. I am at a loss here, what else should I do to get it firing? Thank you all for your help and wisdom.