I have a 2000 Hyundai Elantra which for over a year, incrementally would not start after it had rained. It would crank, just not turn over. We bought a brand new battery after the last time when it finally wouldn’t crank at all, just clicked as it was dead. After replacing the battery, it went back to the symptom of just cranking with no turnover. My auto-mechanic father in law looked at it while visiting and said he couldn’t get a reading on the ECM, and that all the electronics were jumping all over the place and my best bet was to replace the ECM. We replaced the ECM and sure enough, it started up like a brand new car and has run and started perfectly for one month rain or shine. Now suddenly this morning after a normal rainy night (on the Oregon coast) it once again is doing the same crank, but no turn over. The ECM is brand new and had initially fixed the problem. Any suggestions would be helpful. We’re literally stranded without a vehicle since our Chevy Tahoe’s passlock has disabled our use of that vehicle at the same time that we finally fixed the Hyundai. Just our luck. Thank you!
Sounds like water in your power distribution box. Usually located under the hood on drivers side. Also may be some relays , etc on the firewall. Look along the edges of your hood, and locate likely problem areas under those spots: bad wires, loose connections, bad weather-stripping, etc.