1990 F250 Wont start... Need Help

[gusd]

I just recently bought a 1990 f-250 7.3 4x4. When i got it it had a little trouble starting cold but within about 3 minutes i would have it started and it would start immediately for the rest of the day. Then a couple days later i went to start it in the morning and couldn't get it to run. Cranks fine but would not start. once or twice it would start for a couple of seconds and then cut off. very new to diesels but just working through what i know. heres what i've done so far...

I started out by testing the glow plugs with an ohmmeter and they all tested fine.

added fuel to the tank just to make sure my fuel gauge wasn't wrong.

Then I changed the glow plug relay. still nothing.

changed fuel pump relay.

checked and primed the fuel filter. seems fine.

checked mechanical fuel pump. working fine.

loosened each injector and all are getting fuel.

I noticed that i am missed an EEC Power Relay... could that cause it not to run? but it ran before...

I need some help... Thanks in advance for your time and knowledge.

-Gus