I recently purchased an 89 RS 2.8 v6. All that was described as being wrong with it was “bad fuel pump”. Upon further investigation I discovered the fuel pump wasn’t getting power which in turn led me to the blown ECM/Fuel Pump fuse. Whenever I tried replacing the fuse it blows immediately. Note the ignition isn’t even turned to the on position. I disconnected the fuel pump relay and replace the fuse and it still blows. I disconnect the ECM and replace the fuse and viola, the fuse doesn’t blow. I reconnected the relay and the fuse is still intact. But as soon as I reconnect the ECM the fuse blows. So this leads me to the question. Is the problem most likely the ECM or can it still be the relay somehow? The wires on the relay harness are frayed some (which I plan on repairing) but the fuse didn’t blow from reconnecting the relay. Any insight or advice would be greatly appreciated. Sorry if this has been posted before but I’m new to the forum and couldn’t find anything that gave me a definitive answer.

I’ve traced the wiring back and haven’t found anything. I’ve since replaced the fuel pump relay as well as cleaned up and heat shrinked the lines that run to the relay right below the plug. The only thing that confuses me is that the fuse doesn’t blow when the ECM is unplugged and everything else is connected. I would think if there was a wiring issue with OPS or FPR it would blow the fuse regardless if the ECM is connected or not.

Double check you ecm service number.
just swap over your prom
https://m.ebay.com/itm/GM-ECM-122730....H0.X1227.TRS1