2000 Chevy 7.4 liter wont start

Somebody please help... I have a 2000 3/4 chevy 7.4 litre with 180k. The truck was running not great but running, so decided to do a tune up, plugs wire ect.. Cheched the cap and rotor were in good shape only removed the cap put cap back on. Put new plugs in and new wires, and fuel filter. Tried to start then backfired, realized had the firing order off. So fixed then then never started. 4 days later, i have replaced the ECM, Camshaft postion senson, crankshaft position senson, tested the ICM (good), checked feul pressure about 58 or so. Verified spark at a few different cylinders... Just cranks and cranks and cranks.. Never tries to start. The weird thing is that we spray in brake cleaner and does n ot even try to start, but we do have spark? We hooked up a nice mac scanner and it was showing that the injectors were not firing so we checked the harness and ohmed the injector on cylinder 2 because can only reach and appears to be good... But nothin? Please