Captain Obvious

"Oh, that's very different.... Never mind."

I had mine completely apart a few months ago, but I don't remember. I would assume it only goes together one way.

The ECU output stage uses open collector Darlington transistor drivers to pull the low side of the injectors toward ground in order to open them. That open collector style of driver is sometimes referred to as "floating" when it's OFF. Ummm... I'm assuming that has absolutely nothing to do with what you're talking about? If that's the case, then I've never heard of it. Give me just a little hint (PM if you don't want to influence the results from others) and I'll see if it rings any other bells?

My pleasure. And if all else fails and you're ready to throw in the towel, I'm about an hour south of you. Once you get over the cold start hump, I'm sure your car would make the drive.

Nothing jumps out at me as being out of the ordinary. I was half expecting to see the #1 wire on the rear side of the cap back by the carbs. I can't really explain how yours works fine with the small half moon to the rear when my car (and all the service manuals) say to put the small half moon to the front, but whatever works. Only other thought I have is that what you were thinking was TDC on #1 was actually TDC for #6. I remember you said that you pulled the valve cover to verify that you were, in fact, on TDC#1, so other than that, I got nuthin'. Anyway, like I said, whatever works. If it's running fine now, then I say don't mess with success, right? Unless someone else has a theory... Great pics by the way.

Yeah, a clear head is a requirement. Let us know what you find when you get back to it. But in the meantime, something to think about: You said CSV above, but I'm guessing you meant thermotime? You verified that the CSV is fine when you grounded 46 and it sprayed when you hit START. I'm thinking that the thermotime or a wiring issue may still be suspect, but I believe you have verified that the CSV good, right? The thermotime has two connections to it: One of them should go to +12 in START (just like one of the CSV connections). The other will be (depending on temperature) either a no connect, or a connection to the body of the thermotime. The body of the device is supposed to connect to ground through the thermostat housing. So, to answer your question... Yes, when the thermotime switches to ground, it grounds connection 46 through the mounting threads where it screws into the thermostat housing. It does not make a ground connection using another wire in the harness. It GROUNDS one of the wires in the harness.

:paranoid:

What an annoying, wretched, painful, dangerous, stressful pain in the arse. Sure glad that's over. Have you cleaned up the bore in the bottom of the strut knuckles yet so you can see what it's supposed to feel like? A little sandpaper wrapped around a gun swab chucked up in a drill does wonders.

Pump never ran? Any idea what was the threshold temp for the ZX fan switch? What other supporting data might I be able to help with? I won't be in any position to further investigate until it warms up, but once that happens, I'd be glad to do what I can.

The ever persistant 280 hot restart issue..There are lots of threads about it and lots of things people have tried to fix it. Here's mine... I put a 10K resistor across the contacts of a normally closed push button switch and then put that switch in series with the water temperature sensor. With the switch not pushed, the resistor is shorted out by the switch and it's as though it's not there at all. However when you push the button, the switch opens, and now you've now go a 10K resistor in series with the water temp sensor. The resistor adds to the water temp sensor, and presto... Your ECU thinks your engine is very, very cold and supplies the "appropriate" amount of fuel to start a frigid engine. Worked so well for me that I even disconnected my cold start valve. I just push my "electronic choke" button. Supporting info? Here's resistance measurements I took last fall from my air and water temperature sensors after shutting down my motor. All measurements are in Ohms. 0 minutes after shutdown: W=250, A=1900 2 minutes after shutdown: W=226, A=1640 4 minutes after shutdown: W=231, A=1530 6 minutes after shutdown: W=245, A=1450 8 minutes after shutdown: W=268, W=1350 Some conclusions? a) The temperatures of both sensors goes up after the motor has been shut off. No surprise there. The water temperature seems to crest somewhere between 4 and 5 minutes after shutdown. c) The air temperature sensor temperature is still rising even after eight minutes of shutdown. My theory, which is mine, is that the ECU is seeing the temp sensors and injecting a very small amount of fuel because it thinks that's all the engine needs. On edit - Forgot to mention... This coming summer, my plan is to refine the system a little and use a relay instead of a push button switch. Wire it such that when the key is in "START", the additional resistor will be inserted in series, but once the key moves to "RUN" the resistor would be shorted out and the WTS readings would be normal. That way I won't have to push the "choke" button. It will all be automatic.

I hope the OP comes back after looking into it some more. (I hope that all our chatter hasn't scared him off! )

Not buying it. I just took a look at my ECU notes, and pin #21 is not populated. The ECU has absolutely no idea what's going on with the thermotime or the CSV or pin 21. There are two "power" signals into the ECU. Pin 10 which is hot in "RUN" and "START", and pin 4 which is hot in "START" only. We're getting a little off topic here, but here's my full read on what happens when starting the engine. All engines need a richer mixture in order to start, "irrespective of the cooling water temperature". They use pin 4 to tell the ECU that the engine is attempting to be started, and the ECU responds by injecting more fuel than would normally be required based on the current AFM, WTS, ATS, and TPS signal inputs. That's the phase "Start Enrichment" referenced in the pictures and text you posted. Since this signal to pin 4 will be present irrespective of the cooling water temperature, it will cause the ECU too add some enrichment even if the engine is hot enough that the thermotime and CSV will not operate. After the engine starts and the key is released from "START" back to "RUN", the 12V on pin 4 goes away, but the ECU continues to hold the injector pulse widths longer than would normally be required based on the current AFM, WTS, ATS, and TPS signal inputs. This is the phase "After Start Enrichment" referenced in the pictures and text you posted. This "After Start" phase gradually decreases from the time the key is moved off "START" until this enrichment is completely gone. At that time the injector pulse widths are based solely on the AFM, WTS, ATS, and TPS signal inputs.| I haven't traced the signal, but I would assume there is a simple R-C circuit on pin 4 that performs this gradual decrease feature. As for pin 10, it's the power to run the ECU. That's where it get's the energy to operate.

And even after all that typing I did earlier (certainly too much), I didn't address this issue... If you did in fact connect the thermotime 45 wire to ground and then hit START, something should have gone up in smoke. I suspect that you grounded 46, not 45. One small digit. Big functional difference. And if in fact that's what you did, it points to a problem with the thermotime switch. I know you just replaced it, but if the CSV opens on START with 46 grounded, then the problem is on the ground side (thermotime side) somewhere.

I don't believe so. I suspect the pin you are thinking of is pin 4 which goes hot in START. That would be the signal to the ECU of how long ago the engine was started. And The ECU already knows when the engine is cold due to the water temp sensor. I'm no expert, but that's my read.

Wade's info is from a 1980 ZX, not a 78, and while the concepts of the cold start system are the same, I wouldn't assume that the systems are identical. For example, things that caught my eye in his thread... a) He drew in a relay between the ignition switch "START" signal and the cold start system. You don't have that relay. You're "START" signal comes straight from the ignition switch. No relay. There might be a relay on the ZX, but you don't have one in that location on your 78. He referenced wire colors in his text that may or may not apply to you. Looking at the 78 diagrams, seems all the cold start wiring is green or black. Both sides of your thermotime sw are black and everything else is green including both sides of your CSV. The point is not to get hung up on wire colors like the yellow/white that are referenced in Wade's ZX thread. You don't have a yellow/white. So while the system concepts are the same, I'm not sure you can count on the specific details. You have a yellow/black wire coming off the back of the ignition switch that goes hot in "START". That wire goes to a bunch of things including the starter and the fuel pump relay. It also goes to a connector at which point it changes color and becomes G-4 (green number four) in the EFI system. Once that wire gets into the EFI system, it splices a few times after which, G-4, G-45, G-47, and B-45 (black number 45) are all connected together. Simply put - When you turn the key to START, you should have 12 volts on G-4, G-45, B-45, and G-47. G-47 goes to one side of the CSV and should have 12 volts when cranking. B-45 goes to one side of the thermotime and should also have 12 volts when cranking. The other side of the thermotime is B-46 which connects to G-46 and G-21 (the mystery connection to the ECU). This set of connections (B-46, G-46, and G-21) will be connected to ground when the thermotime is cold and becomes a no connect once the thermotime has warmed up and opened. This ground connection is made through the thermotime body where it is screwed into the engine. Operation goes like this: Key in START - 12 volts connects through the ignition switch to one side of the CSV (G-47) and the heating element side of the thermotime (B-45). If the thermotime is cold and it's internal switch is closed, it connects the other side of the CSV (G-21) to ground. If the thermotime is warm and it's internal switch is open, the other side of the CSV is connected to nothing, and the CSV will not open. So, about that pin 21? Why does the thermotime switch feed back to the ECU? I got two possibilities. a) First is what Wayne mentioned in his thread... That Bosch wanted the ability for the ECU to activate the CSV instead of (or in addition to) a thermotime switch. If they would switch pin 21 to ground inside the ECU, it would activate the CSV while cranking. I don't remember what, if anything, that pin is connected to inside the ECU, but it may have been or a future enhancement. Second theory is that it is simply a test point for being able to check the function of the thermotime switch. Seems Datsun wants you to do all of the diagnostic testing right there at the big ECU connector, and they provided that wire just to allow you to have the ability to measure the thermotime switch function. Without that connection, you would have no insight into the cold start system from the ECU connector. Remember, I wasn't there when they designed the thing, but those are my guesses.

Woof. After all that work. Glad you got off without more serious injury. :hurt: I totaled my first Z many moons ago on 95 very close to you. Maybe there's something in the water?

Naaa. Don't take anything apart if you got it running. All of the manuals say that when you look down into the distributor hole the small half moon should be at the front when at #1TDC, but I guess you could put it wherever you want as long as you adjust the spark plug wires to make up for it. Out of curiosity, now that it runs... Can you take a pic of the engine bay showing the distributor and wires?

Yeah, I'm not sure if it's a trick due to camera angle, but I agree. Here's another pic showing the same. This one is from Blue from the Atlantic Z Car Club (www.atlanticz.ca): Blue's looks a lot more 11:30-ish than mine, but all I can say is that my car runs well, my timing is correct, and I've got more than enough adjustability fore and aft from where it belongs. So maybe mine is off one tooth, but I can still get it timed? Maybe it's a camera angle issue? Biggest issue to check is that the factory service manuals says that when at TDC#1, you should have the smaller bow shape should be placed toward the front of the car. That's what you have now, right?

If you've got the problems sorted out, it's academic, but... Here's what the distributor drive tang should look like at TDC. You're saying that yours is different than this?

Haha! Thanks guys! Just trying to help out where I can.

Haha! Nice. I won't make that mistake, but I promise I'll make one equally embarrassing. Not sure I'll tell you about it, but I do promise to make one in your honor. Probably tomorrow...

Glad you got it figured out. Distributors can be a pain. I was gonna ask about the 1:15 vs 1:35 thing... :laugh:

Couple thousandths. Nothing that I would consider problematic (if it weren't for the fact that I'm having a problem). :paranoid: The shaft is chrome plated for wear resistance, and the aluminum throttle body has steel sleeves in it where the shaft enters and exits. This is annoying... It's gonna be Z season soon and I gotta get to the bottom of this.

I just took a better look at the mounts from the ZX, and the are not the same. The later brackets have a gusset welded in the center to... well... prevent exactly what happened to yours. I suspect they bolt up identically, but if you're looking for concourse replacement, then what I've got is off the table. Here's one of the ZX mounts PS - My 77 also has the reinforcing gusset, so they figured it out some time before 77.

Yes, in addition to the rotating spring on the throttle body, there is an extension spring on the linkage located up near the throttle body. It's rusty and should probably be replaced, but it is there. There is also another spring right at the gas pedal. The weird thing about this sticky throttle body is that it is perfectly smooth and easy to rotate when there is no vacuum behind the butterfly, but when there's high engine vacuum at idle, it gets stuck a little above idle. Kill the motor, and it shuts to the stop screw. Wrapping that throttle body return spring around an additional turn might prevent the issue, but I don't think weak springs are the root of the problem...