Zed Head

If you are super super lucky. He's saying to find a way to hold the valve stem up so it doesn't drop in to the cylinder if the piston is down. You could also rotate the engine to bring the picton up so that it will hold the valve up while you collect those parts that are scattered around. Or you could remove the spark plug and fill the chamber with rope or tubing. Many tricks. Don't rotate the engine until you have a plan. In the meantime - have you removed the spark plug yet? If the electrodes are all smashed up that means there's been valve head damage and the head will have to come off. You can also shine a light in to the hole to see if the piston is up. You can learn a lot just by removing a spark plug.

Hiccups and loss of power, backfiring, bucking....those are the typical signs of running lean. A common problem with the old EFI systems. Not really clear why, maybe old electronics, different fuel, maybe the system was tuned to perfection for fuel economy. But there's a common fix for it, the potentiometer that I mentioned. But, before that, fuel press ure is critical to correct performance. You have to measure it, there's no easy way to tune around it. It has to be right. There is just a long list of small things that need to be done to get the engines running right. People rarely resurrect one of these old cars and are happy with the way it runs. Here's that fix, for after you check the other stuff. Get those engine and head numbers, just for kicks. There is a wide range of possible combinations that you might have. http://www.atlanticz.ca/zclub/techtips/tempsensorpot/index.html

Not clear which wire is "missing completely". I have a vague memory of a red wire being part of the coolant temperature sensor harness. It has two bullet connectors in between it and the ECU. (It's where people tap in to add a potentiometer). The best thing to do is to work through the EFI system tests, and give the engine a complete tuneup. Find the engine and head numbers and it might help ID the engine. 78 has the N47 head, everything before has the N42 head. The engine serial number will give an idea of year of manufacture. Engine swaps are very common. The N47 head wouldn't have come with the switch in the thermostat housing. The N42 head would have. Here are the links to the two books you'll need for the electrical testing and tuneup. Do the testing at the ECU plug and measure real numbers not continuity. Good luck.

Ouch. That might be the disaster you feared. Even the valve seal came off. Odds are high that the valve hit the top of the piston. Hard to imagine a scenario where it didn't. Pull that spark plug and see what you find.

@cgsheen1 might be able to help you out. He has a business, Sakura Garage (pasted the link below), that should be close to you. I assume that there will be charges, of course, but I'm sure you'll get an honest assessment. Sometimes a rocker arm can pop off and make a lot of noise but with no real damage. @Barefootdan just had that problem, and his engine survived. Surprisingly common with these engines, from what I've seen on the forums. Good luck. https://www.sakuragarage.com/

This might help. I only see four other things that could be connected directly to ground, or have an internal short. The diagram does have an odd parallel circuit in it, for anyone that likes a puzzle. Many ways to figure out a problem.

I seem to recall that you might have a 75 280Z. If so, the diff bolt pattern will be your problem. But, you might try a parts wanted ad on the site. There are forum members with part hoards that might have one. Tell people what you're trying do and they might have suggestions. Your posts seem to be a series of random questions.

The drive shafts (2 of them on each car) will, but the propeller shaft (one on each car) won't. The engine, differential, and transmission are all interchangeable. Various relays. Some front end parts. Wheels.

Spark plugs on the Z engines are about the easiest you'll find anywhere to remove and inspect. If they're dry you'll know more, if they're wet you'll know more. Why wait?

p.s. if I recall right it's a 74 260Z with carbs. So many electrical problems it's hard to keep track... Pull a spark plug and check for wetness. With carbs, when you smell fuel it usually means that flooding/fouling has occurred. Might be because you didn't have spark, maybe. But even if you solve the spark problem, if it exists, flooding will still stop it from starting.

Some coils have instructions to mount them straight up, not sideways. Maybe there's a reason. It would be interesting to see if there are any ID marks on it. https://www.cpperformance.com/instructions/120-8202.pdf

The Engine Electrical chapter shows all of the pins that you can check at the plug for a short to ground. If it was me I'd just unplug that plug, set my meter to beep for continuity and poke, poke, poke. The beep will be the problem circuit. Edit - actually, the beep would not be the best signal. You'll get a beep through the relay solenoid. Best to read resistance. The one close to zero is the problem. Then find that pin in the wiring diagram and follow it out. Here's another circuit, after the relay. If you find that the ignition relay itself is good then check each pin after the ignition relay. The relay will pass plenty of current to blow those fuses.

Here's a picture of my old ignition relay, from a 76.

Don't go bigger on the fuses. There's nothing on the Z's that will pull 40 amps through one circuit, I think. You must have a short circuit after the ignition switch. Could be the ignition/accessory relay or something after it like the ignition system (coil, etc.). If your car was or is an automatic there are two inhibitor devices that could be shorting. The simplest starting point is at the plug to the ignition switch. Unplug it and check the black with white stripe for continuity to ground and the same for the black with yellow stripe. That will split the system in to two parts. You have a dead short after the switch. SteveJ just posted. Better see what he said...looks rational (of course). So, there's two separate things that you can do to narrow things down.

Might be that the engine was hotwired, or the PO tried to hotwire it and did it wrong. Might be that the PO replaced fusible links with full gauge wire. Lots of "might be's". If you had a coil blow up just by connecting the battery, that's a sign of major wrongness. Better get a meter and start using it. You really really don't want to smoke the wiring in the harness. You can test everything you need to test without connecting most of it. You don't need a coil yet. You don't even have enough information to choose a correct one. Also, Nissan did not use the standard red for positive, black for negative on their battery cables. Make sure you know which is which. The colors won't tell you anything. Good luck.

Was the engine running, or the key on? I'd guess the P.O. connected the blue coil negative wire to a ground terminal or shorted it out by accident, you turned the key on, the coil overheated and popped it's top. Is that a Blaster or did the PO just paint the stock coil red? Download the 1980 EFI book, and the Factory Service Manual if you want to figure things out quickly. Replace and hope doesn't do well on the EFI cars. No offense intended. If the PO bypassed the ballast resistor then he/she probably did something with the ignition module. Might even have a ZX distributor on there.

Looks like you can still find NOS stuff out there. I'd pick a few links but the Google page has too much good stuff to choose just a few. https://www.google.com/search?q=heathkit+cp-1060&rlz=1C1SQJL_enUS862US862&oq=heathkit+cp-1060&aqs=chrome..69i57.13132j0j15&sourceid=chrome&ie=UTF-8

Maybe you're thinking of this saying...

Do you have a picture of the exploded coil? I've never seen one or heard of it happening. An internal short could pass enough current through to heat it up rapidly but even then the negative terminal wire and positive terminal wire would have to pass the current, and the negative terminal would have to supply a ground path. If the ignition module was shorted or the negative post wire shorted to ground, the coil could heat up more slowly and maybe get hot enough to smoke or something. Either way, the coil itself would only be the cause of the "explosion" if it was internally shorted, and there was a path to ground on the negative post side.. More likely that the source of the failure is somewhere else. Better check the other components before you get carried away with new parts. Heat comes from current and current only happens when the circuit to and from the battery is complete.

Sorry for stirring things up folks. I got carried away with what seemed funny about the first post. "Spend $14,000...you're welcome." Funny.

What year Z and is the ignition system the factory stock parts or has it been modified? Primary resistance is your main concern. Welcome. Most people don't get exploding parts to help them diagnose a problem.

Edited/ The video was pretty funny, I thought, but doesn't help anything.

Edit - I should not have replied to the post. Should have let it fade away. Sorry. (Removed some stuff here). I only posted the graphic to show the physical distance. I did a Google on the name and zip code (weird that zip codes are global).

Edit - I wrote the below while you posted. Another simple check of just the lines and system up to the calipers would be to disconnect both calipers and place the ends of the lines in two containers. Sit in the drivers seat and pump the pedal a few times (don't bang the MC piston off the end of the bore, use short strokes). If the lines are open and pressure is fairly balanced you should get about equal volumes in each container. If you don't then you can just go backward toward the MC. Disconnect at the switch and make some stubby lines to check flow there (you have a number of old pieces laying around by now). Do the same test. Since there's only a single line for the fronts to the switch there's no reason to go above the switch. There's no left-right up there. That will break the system up in to three parts - the calipers, the lines, and the switch.

Don't they use the same calendar in Neuvecelle as the rest of the world? This thread is 13 years old. mikewags hasn't visited the site since 2010. Welcome to the forum.