Agree, need more info. Was this a running engine that you started having trouble with? A car you just bought and trying to crank? Have you checked the grounds?
I've had this car for 17 years and it has been running the entire time. It has never failed to start before. Just about everything mechanical in the drivetrain is new or has been replaced.
I have checked the grounds and rechecked them, everything appears to be well grounded, but I will take another look at everything electrical.