Need info on what '77 Volt meter reading should be

[Guest Loose_Screws]

What should the volt meter reading be on my '77 with:

 

1. Ignition off?

 

2. Battery disconnected?

 

As of right now, the volt meter remains pegged negative, regardless of whether ignition is on off, battery disconnected, or cranking the engine over. I can turn the engine over with the starter without any hesitation. The buzzer works as well. Turn signals are a little slow. The really curious thing is that my windshield wipers only work when I am cranking the engine with the starter.

 

I am continuing to search for this electrical gremlin. It all started when the car would die whenever I turned on the headlights or pressed the brakes (IE - current draw). This problem would come and go, but since the car has sat up for a year now, it refuses to cooperate.

 

I should also mention that during this troubleshooting process, I replaced the fusible links with a power distribution block and BUSS fuses. I have also connected and disconnected the alternator entirely, seems to make no difference on the voltmeter.

 

Anyone have any ideas?

[Guest Loose_Screws]

Think I have found the problem.

 

After checking the fuse panel and tracing out the wires in a wiring diagram, I found a wire from the fuse panel that goes to all of the gauges is grounded. I have hoping that this is bleeding over into other circuits and is what is causing everything to act up.

[Guest Loose_Screws]

I added the .PDF of the full wiring diagram to the downloads section. Assuming it is approved, it will be there for you guys to reference.

[Guest Loose_Screws]

Well, I've got the Z running again. I think I may have been chasing a ghost as far as the wiring. I kept checking circuits/wires with a multimeter for continuity. As as I was isolating circuits, I realized that I would get a 'beep' on the circuits with bulbs such as the gauges.

 

The car not running and the injectors staying open was actually a Megasquirt problem. At some point (car has been down awhile) when I was trying to get it running again, chip labeled U7 fried. I just replaced the chip and fired it back up!

 

So, anyway, I guess in a way I am hijacking my own thread? LOL...there were no responses, but a few views, so I decided to tell what I was doing and what happened.

 

Overall, I learned tons more about wiring on a Z. Actually, it's not really that bad, but some bad choices were made by Datsun/Nissan. If you start unwrapping the harness coming from the fuse box, you will notice that a single wire is T'd off, the T'd again. I am no expert, we know that, but doesn't that lead to a circuit overload if too much current is carried?

 

My next job is to actually remove the EFI harness and replace with a complete custom one I will make. My intention is to have Megasquirt control fuel of course, but also ignition, fuel pump, and probably my electric cooling fan. It'll give me a chance to learn more about wiring, but hopefully not screwn anything up.

[Kevin Shasteen]

Way to keep at it.

 

When you are trying to check for voltage be sure and put your negative lead on different grounds. Electrcial components whose metal body acts as its own ground will cause voltage to return throught the body to the battery. So one ground that looks like a ground to you may actuall carry voltage.

 

In other words, one ground will carry -negative voltage when your negative lead touches it whereas another ground will carry zero voltage...just something I noticed on my z.

 

I know every time my Z has an electrical problem, as frustrating as it can be at times, I always end up learning something I didnt previously know before the problem.

 

One thing I know, and that is I would never get anywhere if I didnt have a factory service manual. The electrical diagram is priceless.

 

Luckily for me I haven't had to go into the dash wiring yet.

 

Kevin,

(Yea,Still an Inliner)