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Datsun 280z with 5.3 LS: Having some electrical problems.


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Hey guys, my car has been having a little bit of an electrical problem.  The car will not start unless it gets jumped.  I went out and bought a new battery, terminals, spark plugs, spark plug wires, and even an alternator.  The volts are constantly moving up and down, and every time I give it a little rev, it sounds like it wants to cut off or eventually does cut off.  

 

I'm pretty new to all of this, if someone could chime in and help that would be GREAT.  The only reason the car is running, is from a jump.  After I shut it off, it will not turn back on by itself.

 

Here's a video for a better understanding.

 

https://www.youtube.com/watch?x-yt-ts=1422579428&v=K2v9Hi6CsGQ&x-yt-cl=85114404

 

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Looks like a bad alternator.  Even though you replaced it.  The need for a jump with a new battery suggests a short, killing the battery, then when you jump it, the load from charging the dead battery, or the short, or both, kills the alternator again.  I would first verify no short circuits.

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If you don't know how to find a short you need to find some help.  Replacing more parts isn't going to get it done.  It may not be a short but that's one of the simplest electrical problems to diagnose.  It could just be something always on and killing your battery.  If that's the case, you'll get a spark when you reconnect the battery and everything is supposed to be off.

Edited by NewZed
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If you don't know how to find a short you need to find some help.  Replacing more parts isn't going to get it done.  It may not be a short but that's one of the simplest electrical problems to diagnose.  It could just be something always on and killing your battery.  If that's the case, you'll get a spark when you reconnect the battery and everything is supposed to be off.

 

Yeah I got someone that's going to look at it sometime this week, and hopefully we can find that short or whatever it may be.  Thanks man

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Looks like a bad alternator.  Even though you replaced it.  The need for a jump with a new battery suggests a short, killing the battery, then when you jump it, the load from charging the dead battery, or the short, or both, kills the alternator again.  I would first verify no short circuits.

 

My experience with a short would cut the engine and then it would fire back up to life.  However, if this is the case, I would strongly suggest looking at where the battery positive cable connects to the alternator.  If you are using JCI mounts and the "stock" alternator position for an LS1 (from a Camaro), it mounts down low on the driver side.  The battery connection to the alternator is very close to the JCI mount.

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What engine harness? Assuming its a 1 wire alternator, does it have the proper resistor in the exciter wire? Verified +12V to exciter wire?

 

Have you had the alternator checked, or checked output voltage?

 

1. Load test batter

2. Check alternator output voltage (sounds like this is erratic)

3. Verify exciter wire voltage and resistor.

4. Detailed report back

 

Electrical stuff can be a PITA to diagnose, but that should give you a good leg up.

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Having the same problem with an LS1 swap. We could not find the power drain, so I just installed a battery cut off behind the passenger seat. Now the issue is remembering to turn it of the off position when I park the car.

Edited by GeeZ
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Battery cut off is always and option however all power drains can be found. All you need is a good multimeter, electrical drawings of the car in question, some familiarity of how the new engine was wired into the existing electrical system and a lot of patience. Electrical/electronics knowledge would not hurt either.

Troubleshooting an electrical problem on the forums is not going to be easy as there are so many varaibles to consider not to mention all these cars are not wired exactly the same especially when you do an LS swap. Good luck sir, electrical problems suck but I think you are taking the right approach and have someone take a look at it.

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