Turns over but wont start................

An engine needs fuel, spark and mechanical integrity to run. Fuel pressure and volume is easy to check (even "opening" a fuel line while someone cranks the engine over will verify the presence of fuel but won't verify pressure or volume). Ignition spark is easy to verify and after that plugging in a scan tool to the 16 pin diagnostic socket under the dash can verify the operation of a lot of key engine sensors. Had the truck been running "normally " prior to this no start condition or had the check engine/service engine soon light been on?