Muh240sx

I’ve searched all over for answers pertaining to this problem, and I hope this is in the proper section to get help, but basically as the title says, my car will die and refuses to start acting as if it has a bad battery despite me just getting a brand new one a month ago.

Basically I bought a used two owner 1989 240sx two tone coupe that?s been in a family forever for a okay price, and it?s got minimal rust. The car had been sitting since 2018 after it had gotten about $7500 dollars in repairs of just general maintenance like new lines and new undercoat.
Well it ran fine up until early November when after I had done some tinkering with the radio and speakers and my buddy forgot to unplug the battery while I was working on the cars radio, one simple job. Basically I noticed after that the car ran fine for awhile radio worked great and suddenly it just died, so I attempted to start it without the radio and I got it running for a minute before it died and acted like it had a dead battery, so first things first was to replace the battery, which I did, and to no avail. I drove it 30ish miles before in decided to start stuttering like it had no fuel or power and died, I got a jump from someone and it cranked right over, only to die not more than a quarter of a mile down the street. So I dropped the battery on the charger and hoped it would run fine which it did, for 20ish miles before leaving me stranded once again. So I cleaned the IACV valve, MAF sensor, changed spark plugs (not part of the issues just wanted to) cleaned up the throttle body and put a new battery in again in case I had a faulty one, and still nothing ran for 20ish miles again and almost died until i mashed the gas and it acted like it wanted to die but it kept going, wouldn?t go over 5-7 miles an hour until I got it home and it?s been sitting since. I?m confused on what to do, and really want to get it up and running as I want to store it for the winter, but I?m having no luck deducing anything.

Thanks again for any suggestions if you guys can toss any my way

zombiewolf513

Check if your alternator is charging

Muh240sx

I did the basic cable thing where you disconnect the black one to see if it keeps running and it seems to be fine it doesn?t die, but if I can get a multimeter I?ll try that out.

FaLKoN240

Check the voltage to the battery while it is running.

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97nismo

Sounds like the alternator

I believe the battery and brake dash lights show up when the alternator is bad can’t recall

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inferno s14

check your battery wires. if stock i believe it has 2 white wires on the terminal.check those little demons out.
make sure you battery terminals are clean and tight.
make sure wire to alternator is tight and little ground is present.
and check is the alt plug is in all the way lol.
then check the actual alternator.

Muh240sx

Update on this whole situation, I changed the alternator out after it tested good but the same issue still happens, shuts down after a bit of driving, This time the lights will stay on inside the cabin, but they’re dim and the blower motor still turns on. Wondering what to do next, I put some HEET in the fuel system to see if possibly the fuel had water in it causing some issues but I haven’t driven it since the last time it shut down on me. I had to push it a 3rd of a mile home and I don’t want to repeat that stuff again.

Muh240sx

Still need help on this

smoked240

Is it shutting down at pretty much the same time? have you tried letting it just idle for about the same time to see if it only happens under load.

Sounds like an alt not charging but you did replace it you said. I would still check the voltage at the alt to make sure you have proper charging volts.

Clean all your grounds and load test your battery even if its new. I've bought 3 brand new batteries before that were bad from the start.

I would get a fuel pressure gauge and monitor your fuel pressure as you drive and as it dies.

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Muh240sx

It?s not shutting down right away, right after I changed the alternator I let it idle for about 45 minutes only thing I heard was a small clunk once and the idle dipped for like 2 seconds and went back up, when I can get a multimeter I?ll check it but I can?t anytime soon with college and shit, I?ll look at the grounds but one thing I want to check is the fender harness? I don?t know if that would have anything to do with it since the whole thing with my buddy not removing the cables but I?ll check that out. Someone I talked to said it could have possibly been fuel pump but I?d rather have the ?experts? tell me if it?s a possibility, I did check all the connections on the alternator and they do seem to be firmly tight but not overly tight. I?ll probably download the FSM and go over all the grounds when I can

jedi03

if your voltage is good, I would lean toward pump going out too...you can power the fuel pump directly or let it idle to verify...45 minutes of idle time sounds like it could be something else like maybe shorting wire somewhere...maybe try shorter course eg around your driveway to mimic your drive so you don't get stranded...

inferno s14

battery terminals like stated before make sure clean and tight. if they are bot clean or tight your car will not charge.
Also check the battery light on your cluster when you turn swith battery light should come on and when you start the motor battery light should go away.

Muh240sx

About the speedo, I took it out just before all the issues started showing up since it?s a digital and I wanted to repair it, after examining it I found two traces on the weird mesh pcb were fried, idk if this has anything to do with my issues at hand possible shorting out somewhere else, but I doubt it honestly

Muh240sx

Those traces being “battery” and “ill +” which I believe is illumination positive, correct me if Im wrong on that

Here’s a photo of them:
https://imgur.com/a/66rl6nk

inferno s14

probably burned the battery light bulb causing your charging circuit to open.

Muh240sx

I?d say that?s possible but I?d been running without a speedo for a month before this whole incident happened.

I did get a multimeter (finally) and I watched as the battery slowly went down, post start it was at 11.84 and went down to 11.56 with lights on and post revving it to 3-4K rpms, so it has to be electrical of some kind. I tested the fuel pump fuses and the relays, and heard the fuel pump kick on. as well as the alternator fuse now that I had the proper tool and it all checked out so maybe the alternator or my battery is bad. Could possibly be some ground is f?d up somehow. I?ll have to inspect it tomorrow since I?ve got time to rip it apart again.

smoked240

Check the voltage coming out of the Alternator. it needs to be like 13.2-14v to be a good alternator. if it's only giving out 12v while running it's not enough and should be replaced

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Muh240sx

Update on this all, after 3 alternators it seems to be running and driving again, but it starts off at 14.3 and drops to 12.6 on the battery, should I be concerned or just let it be

jedi03

check at the alternator...the voltage drop of the wiring can be different...should be 14 volts running...I usually do the load test at autozone, their machine will indicate if faulty or not, they can usually do on vehicle too...however, even my current alternator (after 3 showing low volts at idle) I settled on one that keeps 12 while running...not the best but it works and keeps my battery light off...im sure it contributed to my last battery failing after 10 years...