Zed Head

The fancy named modules, like Accel and Pertronix, just pass more current and create more heat. Better spark at 7000 RPM, but if you're not going to be there it's a waste. I like the decent name brands from the parts stores. I have a BWD from OReilly Auto right now. Get on Rockauto and pick a Standard or BWD. You'll save some money and get a part that will work fine with a 0.7 primary circuit coil.

These rubber pieces peel out and can be replaced. Might actually be under what I circled, those look bigger. Courtesy Nissan had the parts a few years ago. They'll give an extra 1/4" of lift. I think it's why old Z's tend to be tail droopy.

Your test procedure is correct. Discolored module is a sign of overheating. I think that the manufacturers actually include that in their instructions. Since it runs now, and ran well before, I'm guessing you'll see good results with new parts.

Be careful with those newly coated wheel flanges. The coating can get squishy and compress, allowing the lug nuts to loosen. There are stories. Mating surfaces are best metal to metal.

Primary is resistance to voltage passing through the coil and module. 0.2 is low and will cause the module and coil both to get hot. Heat can cause problems. If you're sure of that 0.2 number I'd get a new coil. I would not run that with my parts, and I run some weird stuff some times. You might even be able to feel the heat buildup by touch while the engine is running. Put a finger on the module and see if it hurts.

I realized after I posted that the center post does see voltage. Just across very high resistance. So the 12 volts wasn't wrong, but it was the wrong test. Your numbers don't look terrible but they might be a sign of a problem that gets worse with heat. They're not quite right. Where did you get your specs? 0.2 ohms is very low, even for a GM HEI module. Spec. is 0.6. That would create extra heat. The HEI module does put more work on the coil. If you have a spare coil it would be worth a swap. It's not uncommon for coils to fail when they get hot, then work when they cool off. Ignition modules do the same.

The common test for a short is to measure resistance from one of the terminals, + or -, to the center terminal. It should be in the thousands of ohms of resistance. Like 10,000 ohms.

If you really are getting 12 volts to the center electrode of the cap that would be a sign of a bad coil. Shorted internally. Might be your problem, it would probably get worse as the short caused heat. The distributor cap only sees voltage when spark happens. It will never see battery voltage. You might have found it.

720 is right. I edited my post.

Alright, so I've gone back to a known good spot, above. As I understand it, you eventually hooked up the blue wire and it started working. Maybe it's that temp sensor? Who knows. "Welp, I'm a dummy. I didn't have the blue wire hooked to the coil. It works great now. Perfect response. Now just to figure out this temp sensor. I bought a new one today. Hope it works." Then, some things happened. "Hey guys, so I'm back with more issues haha. So I've been wrenching on the Z for months. It's getting really close to driving condition. I'm just running into another spark issue now. The car cranks, runs, and is quite rev happy when the carb is dialed in. But I seem to have an issue where the car will start, then die maybe 3 seconds of running if the idle is anything under 1500RPM. After I tried all sorts of carb tuning, and idle adjustments, it still wont idle correctly. I pulled a plug wire and did a spark check. Very strong spark, but after a few seconds of running, it stops sparking, and dies." So, maybe the HEI module did get damaged. It's hard to say. You sound confident that you're losing spark, causing the engine to die. You might make sure that the module itself is not losing power. Put your meter on the B terminal of the module and see if it is getting lost before it does. It will show low current, like 10 volts, while the engine is running, but should jump to 12 when the engine dies, if it's not losing power. One other possibility is the pickup coil in the distributor. They have been known to have wiring problems. One odd one is that the vacuum advance moving the breaker plate causes the wires to shor out. Maybe disconnect your vacuum advance to be sure. Measure resistance of the red and green distributor wires also, not voltage. Should be about 720 ohms, per FSM. Sorry. Thought you had it back there in March.

When the engine is not running you'll get the same voltage on both sides of the coil. So that's correct. Seems like your ignition system might be okay and you have some other problem. There are a variety of possibilities. I went back through the thread and you have made progress. You have spark and it does run. But, I see that you have an E88 head, which means that you have carbs. So, that's a whole new twist for a 75 280Z. Do you know what type of fuel pump you're using? Electric or mechanical? Have you measured fuel pressure? What shape are the carbs in? Maybe start a new thread about carbs. People with carbs and Pertronix on a 240Z might not even look at this thread. But they'd have the answers.

That's inches of vacuum, a 0 - 28 scale, in mercury (Hg). A very low number. Looks like a big leak somewhere. Just stare at the engine and all of the various hoses and fittings on the intake system and the engine's crank case. Wiggle things while it's running, squirt some carb cleaner. You'll find something. Post a picture and we'll mark it up with places to look. At least it runs. Once you get the leaks sealed up the idle screw should work.

Not sure what to recommend here. I've offered ideas but then you do something else instead. Did you swap G and W? Not clear what the problem is now. Is it still the idle problem or is it something new? Why do you think the HEI module might be burnt out? Does it not work at all now? The distributor leads don't have a possible power supply unless they're connected the the G and W terminals. Try touching your meter leads together and see what voltage reading you get. Maybe you have a meter problem. Might want to just resummarize your situation.

Bad vacuum leak seems likely. If the intake system and crankcase are properly sealed you can kill the engine just by closing off the idle screw. And raise idle speed by a couple hundred RPM with a single turn. Check the PCV hose under the intake manifold and the EGR system. Common leak areas. The valve cover and crankcase are connected to the intake system so even a leaking oil filler cap can cause a big leak. Injector o-rings are another common leak area. Spraying carb cleaner at various spots is a good way to find a leak. Idle speed will change. Beware though, it will eat paint. Intake vacuum is usually measured in inches of mercury though. Not sure what 6 psi means.

Just mentioned this on another thread. The Maxima L24E. Probably what that AFM was used on. Not sure what Nissan would do differently between the two applications.

On the sticking throttle, one thing about the gummed up throttle blade is that it only happened when the engine got warm. Which might fit your symptoms. If by "kick it down" you mean pull it up with your toe, then that's a sign. Nissan did make a fuel injected L24 engine. The L24E, used in the Maximas. Could be what you had. Might also be that you had an L24 with an L28E head. Check the head markings for that. N42, N47, P79, P90. The Maxima L24E had an N47 head but it had a CHTS, which the 280Z N47 head did not have. That's how you tell them apart. Running rich cold but not hot is kind of odd. Usually they just run rich all the time. Good luck.

What is "which"? Seems like it might work.

As I understand things there are several versions of the E88 head. Some have large combustion chambers and small valves. That would be a "boat anchor" head. Your head though, seems to be well thought out, with larger valves and a known combustion chamber volume. You know what you have and it seems designed for the overall engine package. I've found, in my long and varied history of any type of "bench racing' that people who don't really know what they're talking about are the ones who use terms like "boat anchor". Once the head has been modified it's no longer an E88 head. A better description might be that it's an "open chamber" head (to distinguish from the squish type P79 and P90 heads), with 35 and 44 mm valves, and 44 cc combustion chambers. E88 is what it used to be.

I haven't swapped a head. But, your E88 is probably not much different than an N42, if it has the same valve sizes. A P90 has a larger combustion chamber and will lower your CR. And it has the same valve sizes. So, basically, all you'll get is a lower compression ratio. You will get some "quench" but, even though quench is supposed to be a good thing, it's not very clear that Nissan's quench really offers much. People talk about the theory and the principle but the actual benefits are hard to measure. Plus, you have to get it just right or you end up creating a problem. https://help.summitracing.com/app/answers/detail/a_id/4941/~/engine-basics-–-quench

How hot is too hot? So, the temperature sender is what got hot. p.s. I was wrong about the line bypassing the head. Since it feeds from under the thermostat it does flow some coolant from the same place the normal coolant would flow.

This has come up before, and I don't know how the Sakura product is adjusted to set ride height, but preload can make the low speed ride stiffer. If you adjusted ride height by compressing the spring you would add preload. You might see if you have used the wrong method to set ride height.

You can find a lot of discussion and conjecture about how those lines are important during warm up but Nissan doesn't mention them at all in the Cooling chapters, for the carb'ed or EFI engines. The thermostat's have a small hole in them to let coolant past so there is flow through the head. Edit - This is wrong, my mistake >> ((The line doesn't flow through the head anyway, it actually flows around it.)). Just pointing out that some of the internet stuff is from other people's imagination. No offense intended to the imaginators.

So it's been sitting for 14 years. It could be that the gas in the rail and injectors dried up and the residue gummed up the injectors. But it should dissolve with time and motion. Or that it didn't dry out but has lost its volatility. You might disconnect the starter solenoid wire, the little yellow one that will pull off by hand, and turn the key to Start to let the fuel pump flush out the lines and get some fresh fuel sitting on top of the injectors. Then, if it does start but runs rough take a screwdriver and tap each injector. A sharp tap can break a stuck injector free. Then, if the that works take it out and give it a mild thrashing to loosen things up. The engine in my car sat for ten years and it runs great now. Good luck. Welcome.

Which ones?

McMaster Carr is easy to order from. Very quick. they've even improved their web page so I can paste links now, and get fairly close. https://www.mcmaster.com/#bushings/=1e57wtr I'd go for drill bushings.