just installed rebuilt engine. engine starts, runs like a top for 10 -15 seconds

No chaffing or shorted wires to the fuel injectors, vacuum hoses all in proper place, good vacuum to the hoses, fuel pressure regulator not leaking, injectors all in good shape, did you use some lube on the injector 'o'rings when installing. We aren't there to check it for you, and you might need to get a mechanic to help you double check the install.