Hi folks-so I had a pretty strange day yesterday in my 1972 240z. Some specs:

-2021 battery, never ran down

-new alternator

-new starter, with new inline "fuse"

 

I installed the new starter and alternator around last fall. Since then, the battery meter in the dash would periodically peg all the way to the right, but only occasionally. Most of the time, it would hover near the middle marking, maybe swing upwards by a small bit when running. I had the car out for 2x 20 minute drives yesterday, and by the second drive, the meter was pegging all the way to the right. I had to gingerly ride the throttle to keep RPM's near 2k to get home, as the car has been wanting to stall out with a hot engine+low idle+fast throttle application(another issue for another day, the 4/5/6 carb is running too rich).  Near home, I gave it a test, and let off the throttle. Sure enough, it held idle with no throttle but the instant I gave it throttle, it stalled. Here's where the issue starts: 10 seconds later, the starter wouldnt even spin. I let it rest for 30 seconds, and the starter luckily spun enough to start, and I got home. Also, the sound of the starter is different now. Please see pics of the insulation on the wire; I can't tell if that looks correct or not. Also, I got a mild burning smell near the starter when I sniffed around the engine bay after driving. 

 

I checked the battery when I got home, 12.8V, so I don't think I've got a bad battery. Any ideas as to what is going on? thanks for the help!

20 minutes ago, RJK said:

Hi folks-so I had a pretty strange day yesterday in my 1972 240z. Some specs:

-2021 battery, never ran down

-new alternator

-new starter, with new inline "fuse"

 

I installed the new starter and alternator around last fall. Since then, the battery meter in the dash would periodically peg all the way to the right, but only occasionally. Most of the time, it would hover near the middle marking, maybe swing upwards by a small bit when running. I had the car out for 2x 20 minute drives yesterday, and by the second drive, the meter was pegging all the way to the right. I had to gingerly ride the throttle to keep RPM's near 2k to get home, as the car has been wanting to stall out with a hot engine+low idle+fast throttle application(another issue for another day, the 4/5/6 carb is running too rich).  Near home, I gave it a test, and let off the throttle. Sure enough, it held idle with no throttle but the instant I gave it throttle, it stalled. Here's where the issue starts: 10 seconds later, the starter wouldnt even spin. I let it rest for 30 seconds, and the starter luckily spun enough to start, and I got home. Also, the sound of the starter is different now. Please see pics of the insulation on the wire; I can't tell if that looks correct or not. Also, I got a mild burning smell near the starter when I sniffed around the engine bay after driving. 

 

I checked the battery when I got home, 12.8V, so I don't think I've got a bad battery. Any ideas as to what is going on? thanks for the help!

Voltage is only one indicator of battery health.

First, what is connected to the red wire that is going to the positive terminal on the starter? That load could be part of why your ammeter is behaving the way it is. When the ammeter needle is on the positive side of the gauge, that means current is flowing from the alternator to the battery. After recharging the battery after starting, the only loads that should make the needle move right are the brake lights and horn. Even then, those shouldn't cause much of a deflection in the needle. Other than that mystery load, the needle moving to the right could indicate a failing battery as your alternator keeps pushing current into the battery. It could also indicate an alternator overvoltage condition.

If the battery health isn't good, that could cause issues with starting. The issues with the car stalling could be related to improper re-wiring, bad battery, or something else.

With the car running at around 2000RPM, what is the voltage at the battery?

 

1 hour ago, RJK said:

I installed the new starter and alternator around last fall.

How about a failing voltage regulator?  Why did you install the new parts last fall?

Might just be more than one variable here. Give us a history of what you changed when and why. What was the first symptom back in time that involved changing parts.

Thanks ya'll. So, if memory serves, last fall the car was behaving like it was starved for voltage when starting, and the battery was pretty old, and I did the old "while I'm in there" with the alternator and starter, cause I wanted the car to be reliable and have two less things to fail. Possibly dumb in hindsight, but if you think that's dumb, boy have I got stories for ya. I recall struggling with the new alternator at one point, and going around about internal regulation, as well as the in-line fuse piece for the starter. I will take a battery reading with the car at 2k RPM, and how it behaves relative to throttle, and report back. Thanks.

Was the starter and and alternator failing at that point? The reason I ask is what’s available today is not Mitsubishi. Mostly Chinese junk. Many threads here relating to multiple defective parts right out of the box. Most folks now have it tested before they leave the store for that reason. Please let us know what you bought and where. The starter from the pic doesn’t look like it was a rebuilt original. @stevej has posts out there on how to take voltage measurements on the charging system. It’s pretty in-depth and worth the effort. 

 

If the starter or solenoid gets hot you may have a bad ground connection. Shine up the contact surface on the cable and the block. Might help.

Is the red cable coming off the starter going to audio equipment in the car? If so disconnect that until you get this figured out and move on from there.

 

 

Is the smaller black wire to solenoid where the spade connector clicks on the copper blade looking terminal in good solid shape. I honestly don't know if that could hurt the solenoid but I can't see the connection so I do not know. 😁

4 hours ago, SteveJ said:

First, what is connected to the red wire that is going to the positive terminal on the starter?

How about this?  Should be in your memory.  The other wires look normal.

The red wire to the starter: I have no idea, as it was implemented by a previous owner to me, or original to the car. I do recall that much.

 

Got to the car today. At rest, battery shows 12.8V. I only ran it briefly as it was in the shop, but at idle, this jumped to 13.0V, and around 13.1 or 13.2 at ~2k RPM. The first time I tried to start it, the starter failed. It momentarily spun, and then just stopped. 2nd time I tried to crank it, the starter spun and it started.

13.2 V @ 2000 RPM is not good. As suggested earlier, contemplate replacing your voltage regulator.

The red wire is not original to the car. You might want to see where that wire goes to. Someone may have "fixed" something only to cause other problems.

Need to dig around to find where that goes. Should be easy to find being red. Most professional audio companies use yellow 12 gauge wire for direct 12V supply to a bridge.