Zed Head

The built in tool and parts shelf.

I've thought that only the L24E Maxima N47 came with the cylinder head temperature sensor. Cylinder pressures will be a clue. Especially if it's an F54 block with flat tops.

Oops. Still, check the hoses. My fuel injector hoses were also age cracked and ended up shooting tiny streams of gasoline. Made it all the way to the sidewalk when I opened the hood. Another lucky break, I smelled it in the city before I got on the highway. You have a bunch of small odds and ends in front of you. Have fun.

That would be the cylinder head temperature sensor. That deepens the mystery. It was used in 1980 on the P79 and P90 heads but I don't think the Z car N47 heads got it. That might be a Maxima N47 head. A popular compression ratio "upgrade" for the L28's. @madkaw knows. If you look on the driver's side by the engine mount you might be able to see the block casting number. It should be N42 or F54. I was going to mention the fuel hoses. Make sure that they are all high pressure EFI hose. I'm pretty sure that that glass filter is not rated for 36 psi. Check the rubber hose in the back from the fuel pump also. My car had low pressure hose when I got it and it split while I was driving. Luckily a UPS drive saw the fuel spilling and flagged me down.

It's not a big deal. It will only affect things like intake/exhaust manifold gaskets. Look between the 1 and 2 spark plugs on the cylinder head and you''ll probably see N47 or P79. Check for numbers on the exhaust manifold. They might have used the N42 manifold from the 75. The port shapes are different.

Somebody put a 280ZX engine in that car. Maybe they did the 5 speed too. That would be nice. The intake manifold and the cooling fan ducts over the valve cover are the tell. It should run just like the original 75 L28. Had second thoughts. Probably not. Looks like a 75 manifold. https://bringatrailer.com/listing/1975-datsun-280z-43/

It already has front wheel discs. Download the FSM, and wiring diagram, and Owners Manual before you get too far along. And get a multimeter, it will help a lot with the EFI system. https://www.classiczcars.com/files/ There's also a thread on the forum somewhere about things to do before trying to resurrect an old Z that's been sitting. You can avoid some damage and increase the odds of a good startup. I'd read up on that before even trying to turn the engine over. Welcome to the Z world.

EuroDat added a dotted green line from the inhibitor switch to the seat belt switch. Maybe he had the same thoughts. Maybe the dotted line means maybe. It's not shown in the FSM original. He also changed the closed relay to open. Normally closed seems to make more sense since it would complete the buzzer circuit unitl you opened it by fastening the seat belt. Maybe. Oh well, just another puzzle that Nissan left us.

Or a short to ground. Not as obvious though. At about 2:00.

The coil and ballast resistor won't affect just a single cylinder. They will affect all of them equally. If you have a single cylinder problem it won't be fixed with a new coil and resistor.

One is under the voltage regulator in the engine bay (I think that they're trying to show the oil filter in the background in their drawing ,with the bracket unbolted so that it can be reached), the other is by the fuse box in the cabin.

But they do show the belt switch wires as two green wires, which correlate with the two greens at the inhibitor switch. So, if the buzzer works then stops then the inhibitor is probably getting its power too. Your problem is probably in the ignition relay or the starter seat belt relay, if jumping the inhibitor doesn't work.

I don't know why Nissan calls that relay a Seat Belt relay. Hard to tell by the wiring diagrams. Looks like the seat belt buzzer has its own circuit. They show the "driver's belt switch" here but not in the starting diagrams above. Confusing.

Something that the electrical guys might be able to explain - does this diagram not show power from a fusible link passing through two normally closed relays to a realu coil then to ground? Can't be right, right?

I had assumed a manual. Didn't notice the A/T in the signature. Shame on me. There's actually a relay and and a switch in the starter circuit. The relay is one of those two function relays, connected to the inhibitor switch. So, there's three possibilities there - a bad relay, a bad inhibitor switch, or a bad inhibitor switch actuation. I don't understand how the Inhibitor Switch works, but I think CO and SteveJ do. Might be that there's a seat belt switch that actuates the Inhibitor Switch which then actuates the Starter Relay allowing the starter to function. So, I think you need to consider all of these or just find that wire from the ignition switch and bypass all of it. Notice the M at the bottom, completely bypassing the A/T safety devices. Funny, because the manuals do not have a clutch or neutral safety switch. You can start them in gear.

It's in the circuit too. On page EF-25 of the 76 FSM. I've lost the ability to paste an image.

I think the accessory ignition relay is over there. And if I recall correctly it's in the leak zone.

There is another device on the Start circuit - the cold start valve. Maybe it's drawing too much current. You could unplug it and see what happens. It's the one at the thermostat housing with the large hex base. There's another small one with the same injector style connection but it's the coolant temperature sensor. Don't unplug that one. Edit - actually there's the switch, the thermotime switch, and the injector. One has a heater in it and the other has the injector coil. Unpluggng the switch at the housing takes both out.

I don't think that that diagram is for a 1978. Pre-78 Nissan did have a water temperature switch for the dual point distributors. But 78 uses the single point distributor. And the EGR system uses a heat activated siwtch. The quickest way to narrow things down is to get the voltage measurements from the coil, both positive and negative posts (the coil circuit could be overheating and going open), and the injectors. If it cranks but doesn't start those two elements are most likely to be the cause. No spark or no fuel. Carry the meter and/or noid lights in the car. Measure voltages then insert a noid light if you have injector power. A bad PCM is still a possibility.

But it is the same car and engine, moved from Panama to Spain?

@72 Datsun 240z I would start your own thread, rather than adding to other existing threads. It will help people stay focused on your problem instead of getting distracted by the original topic. Also, since you've already asked your question in another thread it makes sense to respond to that thread. Except in this case where you should start your own new thread. Good luck. Click "Start new topic" at the top of the page.