5.0 nitrous fed solenoid ???

Is the relay amperage rated for the current draw of the solenoids? Is the relay wired correctly? Are the solenoids wired correctly? I know that sounds elementary, but first things first. Is it a double pole relay or single. If double have you switched the hot wires for the solenoids around? If it is a single pole and both hots are to the same pole, the relay is working because one solenoid is working so that narrows it down a bit. Are your grounds good? Try bypassing the relay for the suspect solenoid, completely unhook everything from the suspect solenoid, hook up the power, then just touch the ground to a ground source listening for a "click"