4d55 Won't start. Help?

Ok, finally getting around to firing up the 4d55 diesel motor from the truck that's been sitting a LONG while, and hasn't run since before I bought it.

Key is on, I hear the fuel pump, and see fuel bubbling out at the injectors when I crack a line at the injectors.

Glow plugs are getting power, and they showed the proper resistance when I removed and checked all of them.

Vehicle turns over when they key is turned.

But it won't start.

Any suggestions?

There's fuel at the engine, and power to the glow plugs, and the starter turns the motor over, so I'm perplexed as to why it won't fire up. Or at least give SOME sign of wanting to start.

When you say bubbling out do you see bubbles or is it a nice clean squirt when cranking it over? If there are any bubbles then it wont fire. You got to get all that air out so it has a nice clean squirt. It's a PAI but it needs to be done. It can't build up pressure with it in there. Also is there any smoke out the back. White or black? White + not enough heat, Black = fuel. Nothing = no fuel.

Sorry, it's clear fuel, no air. I'm aware of the problems air causes! Learned that the hard way on my last diesel... lol

No smoke at all. It's not starting...but fuel is going into the cylinders.

injector(s) gone bad or plugged maybe?