Captain Obvious

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...

I've got a pair from a ZX motor... They look the same to me, but I'm no expert. Just sent you PM.

Any thoughts on this?

After you have bolted up the oil pump with the drive shaft in place, it is impossible to get the distributor installed in an incorrect position. There is only one position for it. The distributor drive tang will only go in one way. To fix a "one tooth off" problem, you have to pull the oil pump out the bottom, remove it's driving shaft (again out the bottom), rotate it one tooth, and then put everything back together again. You cannot fix "one tooth off" from up top.

Since it's not going to be Z driving weather anytime soon, I spent a little time on the hunt for this gremlin. I pulled the throttle body off and verified that everything moves smooth and easy. Took it all apart again and didn't find anything astounding. No wear marks on the butterfly. No wear marks on the inside bore. No gunk. A small wear spot where the throttle shaft spins in the throttle body bushings, but not enough that looked like a significant problem. Then I pulled a vacuum on the back side with my shop vac, and it was more difficult to move with the vacuum behind it. Has anyone else ever seen anything like this? On a potentially related note... How many rotations should the return spring receive before it hooks onto the post. It's easy to get a half turn. It's difficult, but possible to get one-and-a-half turns. I don't think I could possibly get more than that. It would certainly be less prone to hanging up if there was more return force. So between those two options 1/2 and 1 1/2, which is the proper return force?

One thing that I forgot to point out is that the process and pics above are for 240 only. In 74 they changed the column design and I've not taken one of the newer "steel ball" styles apart. I'd love to mess with a new one (since that's what I have in my 77) but since the only one I have is on my car, I can't take risks with it without a backup plan.

I don't think you're "really" supposed to mess with it. That said: Start with this: Slide the mount off exposing three screws that hold upper half to lower half: Take out three screws and separate upper and lower: This is the steering wheel end with retainer clip still installed: Pull off the steering wheel taper shoes and the retainer clip: Once you remove the retainer clip, the upper shaft comes out the bottom end of the housing. The spring will probably push it out, but it might require some gentle persuasion in addition to the spring: Tap the bearings out of the housing if you dare. There is one at the top and one at the bottom: Bearing disassembled: There are thirty balls in the bearings so you can count what you have to make sure you didn't drop any:

That's my impression. I'm not sure why they originally thought they needed that grabber in addition to the metal "snuff out shelf", and Datsun seemed to agree in later years. Maybe in the beginning they figured that owners wouldn't want to stick a finger into the bucket of butts to lift up on the other part, but somewhere along the line they decided it wasn't worth the cost? I don't know when they stopped putting in that other piece, but I don't think my 74 had one either. As for depth fitment between the two, I don't think there would be any problems with depth. The older one is a little deeper, but it's only by a sixteenth of an inch or so. I believe there's more than enough dead space below the 280 ashtray that you could put the old one in it's place. I don't know if the depth change was even intentional on their part. Might have been something as simple as a drawing die wearing out at the stampers and the new one was a little different. So here's something for the concourse judges to look for. "Ewwwww... Did you see that red 240 over there with the new style ashtray? I'm gonna deduct points for that!" :laugh:

I was messing around with consoles recently and noticed some differences between old style and new style ashtrays. Here's older (240) on left and newer (280) on right. Note the deletion of the little grabber handle in the later years. Probably a tiny cost savings change: In the later years, they also added the little window for the tray illumination lamp. 280 on left, 240 on right: And, I'm not sure if it's simply manufacturing variation over the years, but the 240 version is just a tiny bit deeper than the 280 version. I'm sure your day is now complete knowing all this.

And BTW, in 74 the water line coming out of the rear carb back to the water pump wasn't metal either. They had changed from the metal flare fitting line you have to rubber braided tubing with hose clamps.

So in 73, did they really use a metal tube off the rear carb for the EGR vacuum? I've only ever messed with 74... Going full bore OEM with a set of flat tops? Most people would tell you you're nuts.

Absolutely! It's not meant to be a press fit at all. The pin is supposed to slip easily in and out of that hole. That's why Datsun went through the expense of using the retainer bolt in the center of the pin. When the pin and holes are clean, the pin would (would?, could?, or should?) float and spin in the knuckle hole in the bottom of the strut housing if it weren't for the retainer bolt.