1988 Other Eagle Models No start / Car kills known good batt

Hi. I have a 1988 Eagle Premier car. It has a 3 litre port fuel injected engine. The car ran fine about a month ago, however, I cannot get it running. If I leave a known good battery {tested at a repair facility}, hooked up to the car with both positive and negative cables attached, this car will kill a good battery. Please advise on how I can go about this. Thank you Roy Phillips