I have a 1990 F150 4.9. I have replaced the fuel pump, fuel filter, fuel lines, and fuel pressure regulator. I have replaced the distributor, spark plugs and coil. I have good spark, and pressure on the fuel rail. The truck will run, but will not start unless I spray some starter fluid into it. Any advice on how to get this truck to run would be great.

 

Do a compression test and see what you have.

 

When you say "The truck will run, but will not start unless I spray some starter fluid into it"

Do you mean it needs a shot of starting fluid to get it running but then it runs until you shut it off ?

Or it runs on the starting fluid and only on the starting fluid?

Believe it to be the latter but not real clear in your wording.

And if the latter you need to verify power to the injectors and the computer is actively firing them.

A noid light is the best method but hand on them feel for a "clicking" vibration, a long screwdriver held to ear as stethoscope etc work in a pinch (don't just verify one).

 

The first thing I would do is check for fuel pressure on the rail.

 

Sounds like a bad computer. I bet the fuel pump(s) are also running all the time the key is on.
In other words the clock in the computer is not running. Maybe from bad caps.