95 B3500 Cranks wont start

[yumaflyman]

Ok I'm usually pretty good at this kind of stuff but I'm now stumped.
95' 5.9 engine
Engine cranks but wont start.
Have 40psi at fuel rail.
Changed coil & crankshaft sensor.
Camshaft sensor checks ok with volt meter during cranking.
Pulled all relays and checked ohms and continuity.
Now I beleive it is the ECU?

For a few days before it quit when starting it would crank about 10 seconds and then start. Now nothing.

Any suggestions? Should I replace the ECU?

[alloro]

1. Have you pulled trouble codes yet, if so what were they?
2. Did you measure voltage across the coil leads with the key on, if so what was it?
3. Did this failure seem to happen when the colder weather started?
4. If you spray starting fluid into the throttle body, can you get it to fire up momentarily?
5. Have you checked for spark by pulling a spark plug wire and inserting a test plug into it?

[yumaflyman]

1. Codes are the normal 12 and 55.
2. Voltages at coil leads were what the book says ( can't remember now) but after further reading I realize I did have my ground hooked to the frame not the ground wire on connecter.
3. I'm in Yuma Az , it is still hot here...
4. I put a little gas in the throttle body and nothing changed.
5. No spark with test plug.

[alloro]

It does sound like you've covered all of your bases and are only left with the ECU as the most likely bad component. Of course there's still the possibility of broken or shorted wiring, bad connections at the connectors, etc.