Zed Head

You bring up a good point, maybe unintentionally. No offense. He has one of these - http://www.datsunstore.com/high-output-alternator-p-1.html Which are wired as "one wire" alternators, apparently, by the description. Maybe he left something plugged in that shouldn't be and it's messing things up. "These are internally regulated units and bolt right onto your z or other Datsun just like a stock alternator. For the externally regulated vehicles, all you have to do is unplug your voltage regulator and tape off the connection. All stock Datsuns use an external regulator up through 1977. You don't have to use the T plug in that goes in the back of the stock alternator either, just tape it off and lay it over to the side." I wasn't saying the alternator is over-stressed, just that it was at maximum output, Which means maximum torque required on the belt. Which is why Oliver specified a special deep V (high contact) belt. Because the stock belts slip.

By the way, my numbers and theory may not be exact on my "dead cell" guess. I think it's more complicated than that But, still, I would not replace an alternator if the battery is no good. You just don't know what's what.

So if the battery is fully charged but reads as bad, that would probably be incorrect voltage. A dead cell maybe (6 x 21 V each). A dead cell would show 10.5 volts (5 x 2.1), but no current flow. And the machine might read the 10.5 volts as bad regulator. Might also be why the alternator is working so hard to charge, pumping out full current and making the belt slip. If you have a meter you can measure battery voltage yourself. While stopped and with the engine running. It will give you more details than the pass-fail of the parts store tester. Not disagreeing with Diseazd,we posted at the same time. But I would fix the battery first and then make sure the alternator is really bad.

Some of the people who run those machines don't really know what the test is telling them. They just hook it up and read the display. Did they test it on the car or each individually? If you have two components testing bad in the same system, you may be getting one affecting the other, giving erroneous results.

Points? You should be able to turn the engine or distributor to where the points are closed (said open before), then open and close them by hand to see if the coil discharges. You can also measure coil voltage and ground at the points. They have to open completely and close for the spark to be produced. Sorry, may not be the best system. I like to follow the paths and see what's not happening that's supposed to.

http://community.ratsun.net/topic/56630-e12-92-retard-or-no-retard/

Which module is on the distributor? E12-80 style with just one connection, or the E12-92/93, with two? Some people have reported problems with the modules that have the extra terminals.

I've spent some time in the south. Y'all is a useful term, and has no simple equivalent. Also spent some time in the Philly area. Around West Conshohocken, and King of Prussia. Drank more than a few Yuenglings in Manayunk.

Neither of those Dropbox videos will play on my system. Don't know if it needs a sign-in or what. He says that it runs now, but very poorly, so the tach and igntion system seem to be powered. Considering that the plugs were fouled when there was no spark, I would install new, clean plugs, set everything back to where it was, and try again.

I was kidding. Curious though if y'all are including the relief volume in your CR calculations. Difficult to measure but should be included.

Burn!

When it didn't start the first time, did you mess with anything before you reinstalled the tach? Plug wires, maybe? Kind of sounds like the firing order is reversed.

Forgot about that. You have an odd problem. Kind of hard to grasp without actually seeing it happen. Just one cylinder losing spark at mid-range RPM just doesn't make sense. If ir were my problem I would spend a lot of time confirming that that is really happening.

Better to trust the test instruments than appearance or newness. If you're positive that there's no spark on #5 you need to fix that. No spark, no combustion, no power, out of balance, rough running. Another way to test is to remove the injector connector. If idle quality changes, that's a good sign that there is spark.

If the alternator and regulator have been swapped from external to internal, the brake warning lamp check replay can cause a drain. You'll see a small spark when you connect the battery cables, and hear the relay under the passenger seat click.. Actually, you'll see the spark for any drain. There's always a very tiny one for the clock though.

One thing not thought about often is that it takes torque to spin the alternator as it produces power. So that 120 amps needs a good tight proper belt to avoid slipping. It could be that simple.

The coil and ignition module put out an electrical pulse when the reluctor passes the magnet in the distributor, and it just follows the least resistance to ground, Shortest gaps to jump along the way. Where the rotor is pointed determines the shortest gap in the cap. Just basic stuff, follow it out and see what you find. Could be a defect in the cap or a stray piece of wire that got in there somehow. The cap is easy to pop off and inspect. The 280ZX distributor also uses the six pointed reluctor so you can't even have a bad tooth to screw things up. Since you don't see current flowing in the wire (no light), it must be at the cap. Could also be that your #5 wire isn't seated properly and the gap is too big to jump (not good for the ignition module, by the way). Reseat that wire and try again.

Take the belt off and see how the bearing feels. Check the water pump also. It has a bearing.

Wan't really clear. If it's only one wire, there's only three things to look at - the plug (losing ground for some weird reason), the wire (losing continuity), or the electrode in the cap. Above 2000 RPM, the rotor will be in a different position relative to the cap electrode as the mechanical advance turns. Could be that the spark is jumping to a carbon track in the cap and bypassing the #5 electrode. Losing one spark is an odd problem though. Are you sure you didn't just imagine it? Over-hope?

Doesn't really fit your acceleration weirdness, does it? No pickup from idle to 2000 RPM with six sparks, and awesome acceleration after 2000 with five? You're testing for spark with a timing light or tester of some kind?

If it is the same car, the nickels and dimes will flow for a longtime to get it in to decent shape. Every little trim piece is probably costly, especially for the 240Z's, and is hard to find. Could be a fun project but you probably won't be driving it much for quite a while. Doesn't the VIN plate look a little beat up? Makes you wonder.

Since "R" is after TDC, and A is before TDC, when the marks are as shown, timing should be at zero, not 5 degrees.

Looks in good shape. Two sources you'll want to at least open and browse through are linked below. Engine Fuel chapter in the first, and the second is a collection of tests covering many years, in the Guidebook. Get the 1980 book, it covers all. There aren't really many people out there "qualified" to work on these old EFI systems. If you know the basics of an engine and how to use a meter you might be best off to do your own work. http://www.nicoclub.com/FSM/280z/ http://www.xenons130.com/reference.html

This is probably the Ignitor kit that you have - http://www.summitracing.com/parts/pnx-1741 And these are the instructions - http://static.summitracing.com/global/images/instructions/pnx%20ignitor%20i%20tests.pdf which say that you want 3.0 to 4.5 ohms on your coil circuit. Resistance is added in series so just add the resistance of the coil to the resistance of the ballast and make sure that the sum is between 3.0 and 4.5 ohms. Since you have a 3.0 ohm coil you can remove the ballast and run the coil without it. You'll be at 3.0 ohms, which is in spec. and will give the hottest spark. That's what I would do.

Sorry, I got my years mixed up (again). Your engine has a cylinder head temperature sensor (CHTS), in place of the coolant temperature sensor used on the 280Z's. It's on the right side of the engine, above the spark plugs, between 5 and 6 I believe. Same style of connector, and you should fine the bullet connectors, I think. As site said, a vacuum leak after the AFM would cause a lean condition also. Easier to find and fix that, if that's the case. Even the PCV system, the hose underneath the intake or the one from the valve cover, can cause a lean condition if it leaks.