Zed Head

Coincidentally, this ZX came up in my email this morning. "Datsun" 280ZX. https://row52.com/Vehicle/Index/JN1HZ04S3BX273855

Put them on the manifold and check functionality. I wonder if there are different versions of the ZX TB's. I spent some time looking at this same type of project and remember finding more reasons it might not work. My TB came a from a 1981 280ZX 2+2. I was using a 78 TB to compare.

As I mentioned above it really doesn't take much force to flex the head. Experiments with longitudinal clamps might show something. If it's bowed up on the ends then it might be as simple as tightening the center bolts first. If it's bowed up in the middle, clamp it from end to end and drive some wedges under the middle of the clamp. Who knows, it might actually be simple to do. https://www.harborfreight.com/1-2-half-inch-pipe-clamp-3813.html

This could be a bad connection at the T plug on the back of the alternator. Seems like you partially realized that something is wrong there. Or, and I think this is rare, and I can't remember if there's not a second L circuit, the bulb in the voltmeter could be blown. That will also kill the charging circuit, assuming that it is the only L wire power source. Looks like they added a second L circuit in 78, with the internally regulated alternator. What year is your car?

How many ohms? What does "good" mean? What does "ground" mean? "That ground looks clean". I can only offer clues. You decide how to run with them. Think in terms of circuits. Current flow. You're losing current flow somewhere.

If the plugs are new you can't really tell if it's running lean. EFI engines are designed to run clean, the plugs don't brown up like an old carb'ed engine might. Could be several things. You need to know fuel pressure at the rail while the problem happens. Leave a gauge on and check it when it loses power. Take the black cover off of the side of the AFM and make sure the counterweight is moving with air flow. It might be stuck. Usually when these engines run lean you get popping back through the intake manifold. Popping and bucking, very annoying. Just a lack of power sounds more like air flow. You can check the coolant temperature sensor with an ohm-meter, at the ECU connection. There's a chart in the FSM. Don't forget the EGR system. I think that it is actuated after the engine warms up.

So you can unplug a single bulb, either side, and power comes back? I don't have a solution in mind but do see that the ground wire for the bulbs is back at the ignition relay. Same for the signal bulbs. You might find that ground wire and either replace it with a better ground wire or clean up the connection. My latest guess is that the ground circuit is opening due to heat from the extra current. Similar to how the bad battery connection open up. Find that ground wire and make sure it's right. It could be the connection at the relay mount or the connector shown in the diagrams.

Are you unplugging each light individually, at the socket, or unplugging the reverse switch on the transmission? You said "them" which implies both, but you have to unplug each individually if you're actually unplugging the lights at the socket.

Do you lose power to the ignition system also? The coil. You're focused on the tail of the problem instead of the head. Go all the way back to the battery. You might even have a bad battery connection. You haven't really said that everything else maintains power, only that certain relays lose power. And don't assume that voltage equals current. Seeing voltage on a circuit just means that it has the potential to do something. Without a ground nothing will happen. Be the electrons...

This is actually a good thing. Now you can look elsewhere for the source of the problem. Try to determine if you're losing ignition power, fuel pump power, or both. That will be a clue.

My mistake on the TB fitting. It must have been the hoses between the AFM and the TB that I was thinking of. The ZX hose and TB inlet is smaller. I thought that there was a bolt pattern issue but apparently not. p.s. edit - although I do also vaguely remember a throttle linkage problem. Worth double-checking, but kind of pointless if you have the other parts. Just like when swapping any of the EFI parts there's always a way to make it work. It's a crude system. The engines all have about the same power from 75-83.

Are you assuming that the larger plenum will flow more air? Your throttle body will not fit if it comes from a 280ZX intake manifold. They're different, the ZX TB's and manifold opening are smaller.

Don't assume that continuity and low voltage mean the relay contacts are making good contact. Sounds like you have a bad relay. The test I described will show you if that's the case. The measurements only get you so far, typically showing what's working correctly. Your measurements have shown you that something is not right in the relay. The next step is testing.

You just described a bad relay. Not sure why your fabbed-up relay didn't work. You're saying that the coil is energized but the switch is not transmitting power. Be the relay. Short across the circuit in the relay that you think is losing power. If it fixes the problem then the relay is bad, either the contacts are dirty or the solenoid isn't working. If it doesn't fix the problem then you can move on from the relay.

It's not clear why the engine needs to be running for this problem to manifest itself. Also not clear that the fuel pump power is the main reason the engine dies. Seems more like you're losing all ignition relay power, not just fuel pump power. Do other things shut down? Radio, heater blower, windshield wipers, etc. Those are accessory items but I think that they use the same supply line to the ignition relay. Also, voltage to the coil should go away if it's an ignition relay problem. Maybe connect a test light or two to your ignition relay's input and output then put it in and out of reverse and see if something different shows up. And don't forget the Hazard switch. It is the cause of many mysterious electrical problems.

The 280Z's have the relay in a bad spot. Gets wet if there's a leak. They're easy to take apart, just bend the crimped lock tabs back and pull the cover off.

Fuel pump control relay loses power on the white/black stripe wire when he shift lever is put in to reverse power is returned as soon as the lever is taken out of reverse Have you tried disconnecting the reverse switch to see what happens? It might not be a high current draw but instead one of the circuits to the control relay is getting grounded, causing the control relay to cut power. The control relay system operation just never sticks in my head. but I think that the oil pressure switch is closed at low pressure, grounding that circuit. Seems like it might be possible that your reverse circuit and oil pressure switch circuit have been swapped. When you actuate the switch, grounding that circuit, it looks low oil pressure to the control relay. Are your reverse lights on when the key is on and engine not running?

Curious as to how an EGR intake adds value to a car. Not arguing, just wondering. That logic also says that a catalytic converter adds value. And EFI. Meaning carbs are bad, since all three of those are for cleaner emissions.

Not seeing it. Can you snap a picture and point it out?

Check the wear pattern on the new shoes. I found that my parts store shoes seemed to be made for a larger diameter drum. The contact points were only on the ends of the shoes. Didn't create much friction. You could remove the lock pin and try to spin the spindle pin to get an idea of whether or not it will come out. Some are easy some are not. If it won't spin it won't be easy.

Sounds fishy...

The fuel pump control system uses the alternator output as a control signal also. So bypassing the oil pressure switch shouldn't have been necessary. Doesn't really make sense, if you're saying that a bad oil pressure switch stopped your fuel pump power., I haven't read the whole thread, it starts off as a turn signal/reverse switch problem.

https://portland.craigslist.org/wsc/pts/d/portland-z-coupe/6939839846.html

Maybe there's something in "SEC 50B".

Maybe it is a Japan market number and the picture got pulled through the translation to English for other markets, unnoticed.