I recently acquired a 1991 240 and the fuel pump relay won't energize.I have power on the main red wire at the relay and on both orange wires when the ignition switch is on. If I ground the blue-green wire to the ECU the relay closes and the pumps run. I hate to replace an ECU and find out there was something simple like a safety interlock I didn't know about. I can jump out the relay and the car runs fine. Thanks for your help

 

Without looking at a schematic, I can't tell you precisely where to look as I've never had this particular problem. I'm sure someone will chime in who has experienced it. I'd say you have a broken, loose or corroded ground somewhere. There isn't an interlock...if it turns out to be the ecu, check eBay as they often are $50 or less.

 

Im new here I have the exact problem ,I believe its the ecu, let me know I m lost here also.