NewZed

Are you sure that the wires to the alternator and regulator in the car are connected properly? Plus a good ground to the alternator case (check with ohm-meter)? And fusible links are all intact? The auto parts store testers are wrong occasionally. You should test with a volt-meter (not the dash gauge) at the battery, in the car, at idle and higher rpm. What is your Charge Light doing?

You mean I could have just suggested moving a wire from negative to positive, without all the extra writing, and looked genius?! An opportunity missed...

Those are both positive power supply to two different components. Two different circuits, with two separate fusible links for protection. Don't connect either one to ground. I gave you the wrong page number above. It's page EF-26, not 36. Not sure why you don't want to take a look. Every time I look through there I learn something new (one reason I like to browse the forum). Those are the fuel injection harness fusible links. The diagram shows that one feeds power through the EFI main relay (72 in, 43 out) to the dropping resistors and the other feeds through the same relay to Pin 10 on the ECU (71 in, 10 out). So you should be able to check the circuit to the relay, through the relay and to the target. You won't get power to the targets until the relay is powered up through the ignition relay. But you have power to the injectors so you know at least one side of your main relay works correctly. Check for 12 volts at the Pin 10 connection to the ECU for the other half. There's a good diagram of the main relay in there also, with the pins numbered as referenced above. I would check continuity from Pin 1 at the ECU to the negative post of the coil. There's a resistor in-line but you should still have a circuit there. If Pin 1 doesn't see what's happening at the coil, your injectors won't fire. I'll leave you alone now.

http://www.datsunstore.com/product_info.php/cPath/37_157/products_id/1026

I am definitely not an expert on the Datsun EFI system (still learning) so can't really answer that question, but I would recommend moving on to the wiring diagram in the 1978 FSM. Page EF-36 shows the ECU, the relays, the power sources, injectors, cold start valve, etc all on one page. Just a quick look shows that Pin 10 gets its power from the electronic fuel injection main relay, which gets it power from the ignition relay. With the diagram and your meter, you should be able to back track to the power sources and make sure that you have good circuits. Be aware that your fusible links can be bad with no external signs. They're designed to contain the melted wire inside the silicone cover. You might check power at the end of those fusible links (the two green wires in your picture) to be sure they're good. The dropping resistors won't show a voltage drop until current is flowing. So you'll get 12 volts on either side of the dropping resistors if they're intact, engine not running, key on. Good luck. Download that FSM, it's broken up in to chapters, easy to use. If you're using the EFI Bible now it's the logical next step, it's more specific to the model. p.s. to the others on this forum who know the EFI system very well, feel free to add any thoughts or corrections.

Here's a link with some good pictures of the later 5 speeds, including the Borg Warner. If the shifter hangs off the back on a cylindrical mount and it's a 5 speed, it's one of the FS5W71Bs. http://www.az-zbum.com/information.transmission.shtml

Power to both terminals is correct. The ECU grounds the circuit, energizing the injector solenoids when the ECU sees the pulse from the negative side of the coil on Pin 1 at the ECU. Check that Pin 1 is getting the signal from the negative post of the tachometer. The tachometer has to be installed for the Pin 1 signal to get through. You might be starting on the cold start valve which only squirts during Start, but not firing the injectors.

I found the same thing with the ECUs. I found that 76 and 78 have the same part number but 78 won't run a 76. The pins are different (look at the pins on the ECUs if you have both). I've also found that my 78 ECU doesn't match the 78 FSM wiring diagram (the cold start valve circuit and a wire to a relay were different if I recall correctly). Did you bring all of the relays over too? That would be quite a job to swap the complete wiring harness. 1978 used more relays and less ECU to control some functions. You might take a look at the wiring diagrams between 75 and 78 and see if you need to add some relays or do some custom wiring. The Engine fuel section has some good breakouts of the ECU wiring. You can get both FSMs from the xenons30 web site -http://www.xenons30.com/reference.html If it starts, but won't run it might also be the fuel pump safety circuit, which is different for 1978, using the alternator or oil pressure switch to keep the fuel flowing.

What year is the car that you put the 78 gear in to? Did you change the wiring harness also?

Is it an LSD? I see the finned cover. That might narrow your options. If you're careful, you can put whiteout on the axle shafts and the pinion, turn the axles in the same direction one turn and count the number of revolutions of the pinion shaft. It's hard to estimate 3.7 from 3.9 but it is possible.

The flywheel can rust and stick to the clutch disc, freezing them together. The pressure plate comes up but the disc (connected to the trans mainshaft) just stays stuck to the flywheel. Way back on the first clutch I ever installed, on a small block chevy engine, I actually put the disc on backwards (the "This side toward flywheel" sticker fell off!). Everything moved like it should but the clutch would not release. The engine was loud too, so I couldn't hear the clutch springs rubbing on the flywheel bolts. Just one more possibility...

Pads are easy to change. Did you toss the old ones? Or just buy some cheap stock style replacement pads as a benchmark.

Thanks. I had a bookmark to a specific forum so didn't get the Facebook link. They're back up now.

Wondering if anyone knows what happened to the classiczcars site? Did they get hacked or did the domain name not get renewed?

That's a good point. There was a guy over on Classiczcar who had his brand new alternator tested several times at the auto parts store and it showed as good, but his measurements showed that it was only putting out 12 volts. You need ~ 14.8 to properly charge the battery. He had to put up a fight to get a replacement. Does your charge light come on before the engine is started, then go off?

Do you have a volt/ohm meter? The 1975 FSM has a thorough test procedure in the Engine Electrical section. Have the regulator tested also. If the regulator is one of the newer solid state ones it might have been damaged when you removed the cable. Or it might have been bad from the start. The old points type might not like the power surges from removing and replacing the cable either. Did everything work right pre-turbo motor?

It looks intriguing but the only benefit that you actually described was moving the harmonics up in the RPM range (even that is kind of subjective). Most of what I've been reading implies that the L6 block is very rigid as designed. Do you have more measured numbers or descriptions of the benefits of adding a girdle? Might generate more interest and discussion.

Interesting. Some ZX's come with 50 amp alternators. I learned something. Watch out for the brake warning lamp check relay wire. 1976 has a wire to it that will leave it on all the time and slowly drain your battery after the AtlanticZ swap. 1975 might be the same. You'll know if you hear a click from under the passenger seat when you reconnect the battery, even though the key is Off. Edit - p.s. - Consider using jumpers at the plug instead of cutting the wires. You'll have the option of going back and it looks cleaner than cut wire ends hanging around. If you do cut wires, be aware that of the ones left over, one is hot always and one is switched so will be hot when running.

You could just unbolt the other side, where the nuts are undamaged, and see what's there. Or, isn't the bolt head visible under the u-joint? The snap-in ones don't have a bolt head there. Or you could probably file or grind that damaged portion of the nut off. Some alternative thoughts.

1975 comes with a 60 amp alternator and an external voltage regulator. The main thing you get with the ZX alternator would be to save money on buying voltage regulators. I don't think that a ZX alternator would be 50 amps either. I think that Datsun went to 60 amps at the 260Z and stayed there for quite a while. You probably have an old external Z alternator. Are you sure it's the alt and not the reg?

In general, the O2 sensor gives information back the computer that is used to lean out or richen the mixture, mostly for cruise conditions. Otherwise I believe the computers use an internal map that assumes a certain injector rate, and uses temperature and air mass to determine how long to hold the injectors open. You have bigger injectors so unless you've retuned the computer (maybe that's what modified means?), it is using the map for small ones, probably adding much more fuel than needed. That's all I know, just a few things in general. You have a mix of parts, the more information you give, the better the advice back you'll get. I'm interested, I've seen a few examples of the 300ZX ECM modification but not a lot of detail on how to make it work well. I think if you search "afshin" and "300ZX" you'll get some threads to look at. I'll bow out now, there's others here who know more.

This observation may or may not help - your first paragraph shows that you are way ahead of where many people are when installing Megasquirt for the first time. Which makes the second paragraph about connecting four wires for power kind of confusing. How could you do the first but not get the second? Just my initial thought the first time I read your post and when I just read it again. The second issue with getting some responses is that your pictures are enormous! I think that they are the largest I have ever seen on this forum. I have 2.5 Mbps upload speed which is middle of the road for internet and it took ~10 seconds to load the pictures. Then they were way too big to look at, I could only see one corner. Many people probably bailed out or thought that their computer was locked up. If you can still modify, I would shrink those pictures down. Back to the problem, I have found that this link has some good basic advice for wiring - http://www.megamanual.com/mtabcon.htm#wire'>http://www.megamanual.com/mtabcon.htm#wire Here is the same page from the top - http://www.megamanual.com/mtabcon.htm

Are you using the stock 1983 ECCS with a working O2 sensor?

You need to post a picture. Just because we want to see it.

List the 5 choices.