I recently got a A/T ‘03 G35 Coupe from facebook marketplace and i realized, upon getting it to my house, that the starter was just clicking on start up. I replaced the starter and it started to crank but, after finding out the fuel pump wasn’t turning on, I was messing with the fuses and i reconnected the battery to check the pump again and the starter started to crank itself over even when the key wasn’t in the car. I put the fuses back the way they were, thinking maybe something that wasn’t working before started working and the same thing happened. I’m starting to think maybe the starter is shorting but i’m not sure to be honest.

Anyone have any ideas?

 

Did you pull any relays?
Provided you wired everything up with the starter properly, it could be a shorted or stuck open relay.

There also should be a signal from the key to a relay.

It is a pretty simple circuit.
You will need a Haynes manual or look it up on line.

 

The starter relay looks brand new almost like the previous owner has dealt with this before. I put a known good battery in and the problem didn’t arise from the initial plug-in of the battery however, Im not certain a bad battery would cause the starter to do that.

Also Im thinking the ECM is bad/not turning on because Im getting high radiator fan when powering ignition to on (not start) and there’s no fuel pump prime. The fuel pump indeed works because I connected straight to 12v and it powered right up; fuel level reads correctly too so i’m not sure. My next step is to check the inner fuse box for possible bad fuses and go from there but at the moment i’m gonna focus on getting the fuel pump to prime unless the starter acts up again.

 

Sounds like relay problem with a ignition key/stalk-clockspring issue.

Yup..you have to pick a problem to troubleshoot.

 

You think a bad ignition switch could cause the issues related to the starter running on its on? Could the ECM not powering up be caused by the ignition switch?