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Which clamp? And where is the fuel leak ending up? Maybe it's getting pulled in to the intake system. At least you know that you have spark. Does the tachometer show engine RPM when it is running?

UPDATE: Thank you for that information. I have unplugged everything I could from the Neutronics device, though I'm not sure if it's affecting anything. However, I've made a big step forward: I can now get the engine running for a short period of time! I don't understand why, but hopefully it makes sense to someone here. Here's what happened: I decided to clean the cold start sensor. While I was putting it back on, a neighbor came over to talk, and I forgot to tighten the hose clamp that connects to the fuel rail. I started the car, and it ran—but with a fuel leak. If I tighten the clamp back down, it won't start at all. I checked the fuel return line to ensure it's flowing, and it's fine. When the engine does run, the RPM is very low. If I increase the throttle to approximately 1500-2000 RPM, it runs perfectly for about 9-10 seconds and then instantly dies. This happens every time without fail.

Actually (I think) this only true if all of the injectors are disconnected. It's a parallel circuit for the 280Z EFI. Batch fire injectors. CO pointed that out way back when I mentioned getting voltage on both sides. Or it might be if the injectors on the same transistor are all disconnected (there's two, either 3 + 3 or 4 + 2). The later sequential systems wouldn't do this. Anyway, I have seen 12 on both sides, which was confusing. But can't remember the conditions under which I was measuring. There are other tricks to test the injectors and the injector circuits. Like tapping coil negative to ground three times. But, it's best to do the simple stuff first, probably.

Stock wire? How green (or brown, I mean oxidized) is the copper? That's a long run between the ignition switch and coil. Oxidation = increased resistance. If you take the ballast out of the circuit is it better?

First thing - the AFM does indeed have a wiring connector, it's of Bosch design (as is the entire EFI system in your Z) and it's, like most Bosch connectors of that era, a PITA to remove. If your AFM is in place it will be difficult to see as it's underneath all that. Second thing - you really need to make sure the injectors are opening. It's sort of easy if you have the right stuff, and can be done in place IF you know how to release and remove the BOSCH injector connectors... If for instance you HAD a spare Bosch injector connector with a pigtail, you could put it on each injector in sequence and use a 9-volt battery to quickly apply and remove voltage to the pigtail wires. Yes, a 9-volt battery will open an injector. If you hear the distinct CLICK of the injector opening you can immediately rule out the "crapolla, the injector is stuck closed". (here I have to say: one side of the battery needs to be permanently connected, the other (doesn't actually matter which) needs to be loose so you can just tap the exposed wire end to the bare pole quickly. You DO NOT want to hold voltage to the injector except for a very brief period of time - that's how they work, milliseconds... IF STUCK they in truth need to be pulled and cleaned (and flow balanced) by a professional shop OR replaced - BUT most of the time I can get a stuck injector opening again by rapidly tapping the wire for awhile (several seconds or more) until I hear it clicking. That may help you in your effort to get it running even if things are not all perfect. The injector is a coil (an electromagnet) so both of those spade connectors are actually tied together by the coil. You should see that when testing with an Ohm Meter - leads placed on the two should show a steady Ohm value. If that circuit is OPEN, the injector is bad and you can't fix it. Now, you can also test that the injectors are getting voltage - they should ALWAYS show battery voltage if the Ignition switch is in the ON (or Start) position. And, because it's a coil, you WILL see voltage on BOTH sides IF the harness wiring is connected to the injector. If the injector connector has been removed you will see battery voltage ON ONE SIDE of the connector an not the other. The ECU asserts a ground to the other side of the connector to open the injector and, like I said, this happens FAST. You will never see this activity with a meter (oscilloscope yes). Because they are basically a coil IT DOES NOT MATTER which side gets power and which gets a ground signal. Most people wire the "hot" side consistently to one side of the connectors, BUT they don't have to! There is NO "+" side or "-" side. If there was, the injector would tell you.

I would like to know the casting code, please, on the 1973 OEM exhaust manifold ? Are you selling a '73 downpipe ?

Hi all and with my profound apologies for not having replied sooner - somehow windows was blocking my logon ! siteunseen and zed head, thanks for your negative assomptions - great attitude between Z owners in the community ; seriously, if you having nothing constructive to say - stfu please or at best - DM the guy with your unfounded fears. :-) Kind regards, Sean

That's a late one. Never heard it. I was listening to them on vinyl on a cheap record player with a penny taped on the stylus.

p.s. did you measure voltage across the injector connector pins or from one injector connector pin to ground. The second way is the correct way. p.s. 2 you're falling in to the "it measured good" trap. We need the numbers.

Did you disconnect the Neutronics thing? The EFI computer is sensitive to the tachometer/coil - signal on Pin 1. I see a "Power/Tach" label on the box, implying that it's also connected to Pin 1 or the coil. If the Neutronics box is shorted it could cause a no-start. Plus, there's no guarantee that it ever worked. Does the tachometer needle move when cranking? I also see some open vacuum lines in your picture. https://www.classiczcars.com/forums/topic/69545-1977-280z-ignitionfuel-system-neutronics/#comment-679115

I tested the voltage going to the injectors and I'm getting right around one volt or less.

As advised by Zed head, I'm going to start my own thread to document everything I've troubleshooted while trying to get this car started. This is my first EFI car, and I'm learning as I go, but I believe I've narrowed the problem down to the EFI system. The fuel pump is running and generating good pressure within the fuel rail. I have found no leaks or vacuum leaks. The AFM (Air Flow Meter) appears to be working; I can see it moving while cranking. I checked the continuity at the ECU pins, and the readings are correct, one pin is slightly higher resistance but looks to be okay. Im not sure if the AFM has a connection that i can take off an clean. looks to be directly wired. The starter/injector relay on the driver's side is clicking over and functioning properly. I've installed a new ignition coil and verified that there is spark at the spark plugs. The car can start with starter fluid but will not continue to run without it. Beyond this, I am unsure how to check why the injectors aren't getting a signal. I'd like to avoid removing the injectors and disturbing the fuel rail for now. My main question is how to troubleshoot why either the injector relay or the ECU is not sending a signal to the resistors, which in turn should activate the injectors.

The tach is back in commission connected to the petronix ignitor 1.5 ohms with ballast resistor. Its a shame you cannot make the 1972 240z tachometer work with the MSD blaster 2 coil. Car was running fine at idle and no hesitation or misfiring even when coming out of long traffic jams. Been fighting this problem for more than 11 years and thought this could be a solution. I guess the MSD blaster coil has more power and keeps the spark plugs clean. Any recommendation?

This is probably my favorite Steely Dan from the only CD I have of theirs. They were a tight playing group on that disc.

Never mind! Coffee kicked in. 3 outer and only 2 inner shims. I read back through that and this doesn't make sense. Diseazed do you know how many valve spring washers Eiji uses? I don't know him like you do and kinda scared to call and ask a bunch of questions until I am actually ready to do mine. I know he's a busy man. Because .080" longer valves are now in the head the springs must be shimmed up to from the bottom to retain the same spring tension. The washers are hardened steel and are there to prevent galling of the aluminum head...don't get them from the hardware store. The stock head came with only one shim under each per spring is exactly .040" in thickness. So just add 2 more under each outer spring (total fo three) and you can achieve the desired increase of .080". Washers used to be available at MSA and were inexpensive. The single stock washer under the inner spring is also .040" thick. But you can only add a total of 2 washers under the valve seal instead of 3, as it won't let the valve seal lock-ring seat properly. The inner spring is more of a "helper" spring and won't be adversely affected, I've had no problems using only 2 washers here and I rev my engine to 7,300.

Have you read datsungarage p79 modification? You shave 80 off, shim cam towers 80 higher and use the valves from the N head. https://datsunzgarage.us/p79/

I do, I ordered another from Nissan to replace mine. When I get back in town from Boston, I’ll post the p/n. Can’t remember if it was superseded.

@Yarb Made a little progress today. I got the reverse lights fixed with the help of Yarb and my little helper was in town too. Yarb sent me a new switch he had. It's longer than the one I ordered Yarb, do you know the part number for that switch?

p.s. Neutronics Enterprises is still out there. Check out the email addresses here - https://neuracing.us/brushless-motor-engineering-and-manufacturing-based-in-sand-diego-ca/ Phone numbers - https://dieselnet.com/com/85.php Stop by and say hello - https://www.mapquest.com/us/california/neutronics-enterprises-inc-366412161 Here's a book that references the patent - https://link.springer.com/chapter/10.1007/978-981-10-5903-2_124

Provide some details about the car. Is it a California car with a converter or is it a Federal car without? There will be a sticker on the door jamb that says Catalyst or No Catalyst. I found the patent describing the concept. If the system follows the patent there will be some hardware attached to the air intake system after the AFM. Attached below. If it was mine I would disconnect it and get the wiring back to factory stock in order to simplify things until you get the engine started. There are numerous reasons that it might not be starting. Start with the basics - power to the coil, spark, tach signal, etc. Download the 1980 EFI book and do the electrical tests. Try starting fluid if you have spark. Make sure the fuel pump is working, etc... I'd also start a separate thread where everything you try is contained. Sometimes people start multiple threads and you can't tell what's been done. It can take a while to get things right after an EFI car has sat. https://patents.google.com/patent/US5163412A/en "Pollution control system for older vehiclesAbstractA pollution or emission control system for retrofitting on older vehicle engines includes a catalytic converter with an in-built oxygen sensor for mounting in the exhaust line, and a supplemental air input line containing a control valve for connection to the engine intake manifold to control the amount of air supplied to the engine. A computer monitors the oxygen sensor output and the engine speed, and controls opening and closing of the control valve according to the detected conditions. The computer also controls the speed at which the valve is opened or closed dependent on the engine speed and optionally the engine temperature, so that the valve can be closed faster at slower engine speeds and opened faster at higher engine speed. The computer is additionally capable of producing diagnostic telemetry, both digital and analog, to assist installation of the invention and test for proper operation once installed."

I live in arizona... i bought it and it just arived in less than 24 hrs. fastest turn around for a relay i thought i would have to wait 1-2 months for.

I just picked up a 1977 280z with a wiring harness for a "Neutronics" system. It looks like it connects to the o2 sensor on the exhaust and possibly the ignition coil. I cant find a single google search about this system or a wiring diagram. I have a black, red and green wire disconnected. Any help would be greatful. If more infomration is needed this is a EFI car. I am trying to get it started. can get it cranking but thats about it.

I have some OEM, two used and one NOS.