A $764 million medical records system is launching at the municipal hospital system on April 2 — even though insiders warn it isn’t ready and patients will suffer. The soft launch of the electronic system Epic is scheduled at Elmhurst and Queens hospitals. “Sooner or later, it will crash,” said one source involved in the project. “There will be patient harm — patient harm and patient death.” Sources say Dr. Ramanathan Raju, who runs the municipal network, NYC Health + Hospitals, is under the gun from City Hall to meet the deadline and fears he’ll be fired if he doesn’t.