96 crown vic, starts and runs 3 seconds, dies

When a motor blows out white smoke that means its burning coolant in the combustion chamber. So a head gasket, A crack some where. Could be the reason for poor performance.

Possible. Cooling system pressure check, compression test and fuel pressure tests are all in order. Do the simple stuff first. The fuel pressure regulator can fail and dump a lot of fuel into the intake and possibly cause these symptoms but what you describe leading up to the "starts but won't continue running" condition does suggest an internal engine concern.