Starting issues...
 

89 240SX stock.

Just fixed a bad exhaust gasket and the car has been doing amazing ever since then up until yesterday morning. I drove from the hospital to my friends house less then 10 minutes away and the car started and ran fine. Went to leave my friends house for work about a half hour later and the car wont start. It just clicks as if its a dead battery but it's not because all my radio equipment and everything works plus we tried jumping it for kicks and giggles and nothing.

So I went to work from 930 till 230 (leaving the car sit for those 5 hours and using my grandpas truck) come back to my friends house and start her... She fires right up... So I shut it off and let it go for a bit try again and she still starts. Well then I go to bed and let her sit leave for work today at 12 and she starts drive to work fine go out to start her again at 2 starts right up...

Now I drive to my friends again at 9 and she started then when Im ready to leave at 10 no such luck... Wait till 11 still no dice 12:45 nothing... Car still wont start and once again acts as if the battery is dead but it isn't. Now I can hear the fuel pump prime when its in ACC and when I start it I hear some other buzzing from the passenger side sounds like its under the car. It only goes on for a bit when I try to start it then that goes away but if I turn it off then try to start it again that buzzing comes back...

Any thoughts? I was at first leaning toward bad coolant temp sensor but when that happened on my 300ZX it would stumble and carry on while driving even randomly shut off on its own then when you tried to start it it would act like this but my 240 seems absolutely normal when it is actually running and driving.

I've also checked the grounds they seem to be doing ok and cleaned the connectors on a few things including the coolant temp sensor.

Thanks in advance

Also I replaced the water pump when I did the exhaust gasket and I believe I bled the lines correctly so Im doubting air pockets though I could be wrong. And I Seafoamed the engine in the gas tank and sucking it in threw the brake booster line. She hated me for that but damn that stuff does wonders Im getting like double the gas millage now (with overdrive off instead of on like I had it before which confuses but Im not gonna argue cuz its much more fun to drive without overdrive).

Ran ECU self diagnostics as well... Code 55...

It sounds like a short to me maybe you have a loose wire hanging thats grounding out and is making the buzzing when you start it otherwise i can't imagine what that sound would be?

I think it may be the starter cuz I hit it with a wrench while my girlfriend started it and she fired right up. Then went down to the hospital let it sit for about 45 minutes and it started again no hitting necessary.

I remember mine buzzing like that. I cant remember what it was though... Yeah, sounds like a short. But maybe Ignition coil. Idk. lol