ok, heres the problem, got a 91 crx and had a b18a1, went to b18c1 w/ b16 head i put the pr3 ecu in and the main relay wont kick on the fuel pump. pr4 will, i jumped the main relay and the car seems to run fine, warm up and drive good. what could cause this to be?? ive tried new relays, tested mine and they all work fine. i tried other pr3 ecus and they do the same thing????????????????????

 

missed a ground wire somewhere? check the thermostat wire, re-do it even if it looks ok.