Hello all, new member here.

I recently got a '76 ,280Z that has been in storage for 5 years. It's been a challenge to say the least. Anyway, I got it running, but the engine won't cut off with the key. I have to disconnect the battery (new battery, but it kills it ???). I replaced the switch but that didn't help. I pulled the alternator and had it checked at NAPA, it was putting out about 15V.

I read somewhere that I may need to install a diode due to a feedback problem, but I don't know where or how to install it.

I really appreciate any help.

ol fiat

Are you possibly running an internally regulated alternator? Like one from a 78 280z/79 and up 280ZX? A 76 was originally externally regulated and that could be your problem.

Thanks

It does have a voltage regulator on the fender that looks original, as is the Hitachi alternator. Is there a way to check the regulator?

ol fiat

The diode is only required if someone has installed an internally regulated alternator. Does the car keep running with the alternator disconnected?

Trying that would at least tell you if it is related to the alternator wiring or something else.

With an older car that has no documented history it is hard to know what might have been done.

When I disconnect the battery cable, it dies. Then it won't restart until the (new) battery is recharged (alternator checked good), maybe the voltage regulator is faultyl How do I check it?

Tried unplugging the alternator with the switch off, no luck.

Thanks

ol fiat

Edited July 17, 200915 yr by ol fiat

FAIW, it's really hard on all the circuitry (e.g. fuel injection computer) to disconnect the battery while the engine is running! While you're diagnosing, and when you need to kill the motor when it fails to shut off, you're much better off pulling your ignition coil wire. (Wear Playtex gloves, so that you don't get zapped.)

Not to hijack , but the term '' cut off '' sounds wrong and slang like. You mean to say '' stop '' . I've even heard '' cut on '' refering to '' cut on the gas for cooking '' . Sounds and looks silly when you type it ! Imagine what non english speaking people must think when they read '' cut off '' for stop !

All due respect, Mr Unkle, but be it ,cut off, shut down, terminate, ceast running, stop, faulter, or just quit. I think an answer to the pertinate question is at hand rather than a grammer lesson.

Thanks

Sure ok no flame intended ! It's not the ''grammer'' it's the slang that others that may want to help just won't understand . ( and I did add an emoticom ) .

On a 240Z, the factory diode is in the external regulator, but it's somewhere else in the later cars, like the 280Z that is the subject of this thread. That's why a 240Z needs an add-on diode when converting to a ZX alternator, but a 280Z needs only plain jumper wires. Doesn't tell us if the diode is the problem here, though.

Back to the beginning. So you start the car, it runs fine. Turn off the key, it continues to run, and you must pull the power to stop it. Here are some questions to help pin this down:

1.) When you turn off the key, is there any change in how the car runs? Stutters, misses, etc.? Or does it run the same as with the key on?

2.) With the key off and the engine still running, do all the gauges still work as normal? Or do they go off?

3.) You mentioned you replaced the ignition switch. Did you replace the small electrical part on the very back (the actual switch), or just the key lock (tumblers)? Or both?

4.) If you leave the battery connected overnight or over the weekend, does the car drain it dead with nothing turned on?

Thanks Arne

1. When you turn off the key, ther's no difference in the way it runs.

2. Yes, everything works even the defrost blower and the radio.

3. I replaced the electrical part of the switch.

4. I haven't left the battery connected overnight.

This car had a lot of modifications done before I got it but the work seemed very good quality and neat.

I feel like something simple is keeping that circuit energized and I'm just overlooking it.

Either the new ignition switch is bad (not likely), or the wiring has been modified or otherwise shorted.

Next test -- start the car as normal, then reach up behind the ignition and unplug the connector from the ignition switch.

If the car continues to run with the switch completely disconnected, we have serious issues in the wiring. If it shuts off (and the blower and radio go off as well), we are making progress. Try this and report back, the test results will determine what the next step will be.