Captain Obvious

You are talking about the water temperature switch, not the water temperature sensor. I'm no expert on the 76, but I took a quick look at the 76 FSM. The water temp switch is closed when cold and open when warm (above 135-145 degrees F). It might do more than the below, but in my quick look I turned up two things the switch does: 1) As described starting on page EC-10 - When the switch is cold, the EGR system is disabled, and once the switch warms up and opens, it will enable the EGR system. 2) As described starting on page EE-26, it controls which of the two ignition pickups are used for non-California models. Non-CA models will used the advanced pickup when cold and the switch over to the retarded pickup once the water temp switch warms up and opens. There is supposed to be a 6 degrees timing difference between the two. You didn't say exactly what went wrong with your water temp switch, but if it failed short (cold), then your EGR system will never become active and you will always run using the advanced ignition timing pickup. On the other hand, if it failed open (warm), your EGR will always be active and you will always be using the retarded ignition pickup. So, your original question... Yes, the car will work without it, but you'll have to decide if you want it to fail "cold" (closed) or "warm" (open).

Zed Head and Willoughby Z, Thanks for the reality check! I didn't even think of the possibility that a previous owner took that stuff off my 77! I already saw that someone before me pulled the EGR system off, and it now seems they pulled the TVV and that heater block off as well. I'm not a fan of the fan either. Here's my plan A... Like I said, I've not yet owned this 280 through a summer yet, so I'm going to play ostrich and hope it doesn't get me. If that doesn't work, the second thing I'm going to try your trick of fooling the ECU into a richer mixture.

xubuntu, It sounds like you (and the guy who wrote that page) are overestimating the power of the AAR. The AAR can not make you run lean. It does not affect mixture. Ever. All it does is boost the cold idle RPM's by providing a temporary air path around the throttle body butterfly plate while the engine is warming up so you don't have to sit there with your foot on the gas to keep it running. There is no difference in operation between pushing down on the gas pedal a tiny bit with your foot and having an open AAR. Unless you push your foot down far enough to open the idle switch on the TPS, then the ECU does not know the difference between your foot and the AAR. If you are running lean on cold idle, it's not the AAR's fault. It simply cannot do that to you.

Good luck with the testing!

My guess would be that the extra heat comes from a bunch of stuff: The pistons, the head, the cylinder walls, the valves, and yes... the exhaust manifold. When the engine is running, parts of those things are much hotter than the water (hence the fact that they are cooled by the water), and when you shut off the engine and stop the water flow, everything will stabilize to a higher temperature before decaying over time. But my point about conduction is that I'm skeptical that the heat being conducted from all those sources would travel any faster to the thermostat housing than it would to something located near the spark plugs. I would expect that energy would conduct at pretty much the same rate in every direction away from the heat sources. What's an AAR pad heating line? I've got a 77 and I don't have any water going to my AAR. Did they put that on in 78? Thanks to Blue, I've been messing with AAR's lately and he told me that later Nissans included the provision to heat the AAR with engine coolant, but I didn't think he was talking about Z's. I thought he was talking about newer stuff. Just remember that the AAR might mess with your idle speed, but it shouldn't do anything to change your mixture ratios. Remember, you're already downstream of the AFM. BTW - Something else I discovered recently while poking through the parts fische was that Canadian Z's included an insulating jacket on the outside of the AAR. Kind of a little "AAR cozy", eh?

Pure speculation of course, but I'm not so sure close proximity to the exhaust manifold is the problem. I would expect something sitting right on top of the manifold might get a little hotter than something screwed into the head on the plug side, but I'm skeptical as to how much difference there would be. I suspect that the efficiency of conduction will mostly overrule even close proximity convection. By that, I mean... I bet that when you shut off the engine, the heat soak will raise the temperature of everything. But that big hunk of metal and the water that's inside it are excellent heat conductors. Way better than the air between the exhaust manifold and the thermostat housing. I wouldn't expect a big difference in temperature between something screwed into the thermostat housing and something screwed into the plug side of the head. Speculation only. I'm not an ME and thermodynamics made me, well... :sick: Nice!

Why? Because I can. Seriously though... I'm not sure my OEM stuff IS working as it should. I'm running rich and for all I know it might be a leaky cold start injector. Honestly, I don't think that's the problem, but if I didn't even HAVE a cold start injector, I could cross that off my list, right? It would just be one less potential leak source, and a little less plumbing and complexity. Just a slightly simpler, cleaner system without it. Granted, not a huge difference, but every little bit helps. Thinking about it some more, the truly elegant solution to fooling the ECU into sending more fuel would be to use the thermotime switch to actuate a NC relay in series with the CTS. That way, it would energize and open the NC relay under the same conditions that it would previously have actuated the cold start injector. (Did I say that right?)

I disabled my cold start injector a little while ago by pulling off the electrical connector. Just to see how the car would perform on cold starts without it, and decide if I really needed it or if I could do without. I've not used the car much since I disabled it, but the results are not that dramatic. The cranking times when "Pennsylvania cold" are definitely longer than with it connected, but they are not "objectionable". I'm assuming that if I were in Canada or Wisconsin, I wouldn't be able to get away with this, but here in PA it seems to be OK without. This is a fair weather car for me anyway and I don't expect it will get a lot of winter usage. I'm thinking I may remove it completely and get rid of that complexity. Pull it off and cap the holes. What say you? Anyone else disabled theirs and have advice to share? I guess I could use a switch to temporarily insert a fixed resistor in series with the CTS to fool the ECU into adding extra fuel through the injectors if I find the cranking times unacceptable. This winter hasn't really been a good test of cold weather starts...

I like it. As good a theory as the others I've heard to date. I picked up a 280 recently, but since I bought it in cold weather and haven't owned it through a summer yet, I haven't had the pleasure of dealing with hot starts after that heat soak. I'm assuming that this summer I'll be in the same boat as the rest of you guys. I've been paying more attention to the "hot start" threads than I used to. You know, if the only thing you're using your pot for is the hot start, you could measure the resistance you need to fool the WTS on your hot start and then replace it with a switch an fixed resistor instead. Two positions on the switch: "Normal Start" and "Hot Start". Simply short around the resistor for "normal" and open the short for "hot". That way, you wouldn't take the chance that you are messing with your mixture at other pot positions. (Unless, of course, you want the ability to do so. )

Yeah, this kind of stuff can be annoying. You can end up chasing your tail. Can you put the AFM back to where it was when it left the factory? Just as a "documentable" starting point? Is there any goop left on the original lock-down location for you to tell where it originally was? I guess it might not matter if the AFM isn't the one that came with the car though... Fastwoman, You're saying that the anti-backfire valve was there from 76-78? The only year that did NOT have it was 75?

Sorry. Got it. No, you explained it just fine. Haha! I'm pretty sure my post #74 is what a brain fart looks like when you take that time to type it out. :stupid: Well I got that pretty picture posted anyway! That's got to count for something, right? Back to reality... Seems to contradict the AFM test results, but I agree with you. Those plugs look lean, not rich.

Here's a pic from that great EFI thread on HybridZ: http://forums.hybridz.org/index.php/topic/95316-braaps-l6-efi-induction-advice-and-tips/ This pic makes it look like CCW is richer and CW is leaner:

I'm really sorry, but I'm confused and I hope I'm not asking stupid questions... I've not been inside an AFM myself, but I'm looking at pictures and I'm getting a different read on the directions that you are... Looking at pictures, the counterweight is in the upper left corner, say 11:00, and it appears to me that if you would move the counterweight "forward", in a CCW direction say from 11:00 to 9:00, then you would be opening the AFM flapper and the ECU would add more fuel accordingly. And if you would move the counterweight in a CW direction, say from 11:00 to 1:00, that would close the AFM flapper, and the ECU would reduce the amount of fuel. Short story is that it appears to me that CCW is richer and CW is leaner. I know it's just a matter of time until I'm inside my own AFM, but until then... I'm confused! When your mechanic was messing with the AFM, was that in an attempt to fix the problems you're having now, or was that a while ago before you started this thread?

I agree that the gas shouldn't evaporate that quickly, but I'm not coming up with any other answer. I've got that wild assed supposition that there might be some siphon effect with the lines, but with the bowls? No way. Once fuel is in the bowl, there's no way it's leaving that bowl unless it leaks out, evaporates out, or is pulled out by engine vacuum. The engine isn't running, so that's not it. It should not evaporate bone dry in less than one week. That's not it. The only thing left is to be leaking out. :paranoid: I, like you, would hope to smell something if it was leaking, but let me tell you a little story... My carbs did not have bowl drains. I wanted bowl drains plugs, so I modified my carbs to include drain plugs and I used copper washers to seal my new drain plugs. It was two or three weeks since the last time I messed with the car, and I checked my bowl levels before I tried to start it. Unlike every other time I did this, the bowls were so dry that I couldn't see any gas through the sight glasses. No fuel on the ground. No gas smell. Car has sat for longer than this, even in warmer weather, and hasn't done this before, so it clearly HAS to be the new drains I installed. I reached up under the carbs, and there was an oily residue on the heads of the drain plugs. the gas had slowly leaked past the copper washers and had evaporated off the drain plug heads. Never hit the floor, but the entire bowl had leaked out and evaporated. That oil residue is what's left after you evaporate an entire bowl off the head of a small bolt. Didn't look like gas anymore. The moral is... Check your drain plugs and the hoses that connect between the bowls and the nozzle for any kind of residue. Might not look like gas anymore, but might be a leak anyway. I'm thinking that if you can keep your bowls full when you shut the engine off, you might not care that the lines have gone dry. A full bowl should easily run the engine long enough to get the pump on-line.

Haha! Well THERE'S your problem! That will unquestionably explain why it takes so much cranking to start the car. No mystery there. So you're done with the "what", now how about the "why?": 1) WHY were the float bowls bone dry? 2) WHY were the fuel lines so empty that it took 20 seconds of cranking before you saw any fuel reaching the carbs? I know it's warmer in AL than PA, but I can let my car sit for weeks without the bowls evaporating dry. As I mentioned earlier, I get a little evaporation over two weeks, but not much. Have you got the round tops that have the drain plug on the float bowls? Maybe they fuel is leaking past that plug and evaporating fast enough that it never reaches the ground. As for the empty fuel lines... As soon as the pump stops moving, there will be no pressure in the lines. It's not like the 280s that attempt to keep the lines pressurized even with the car off. On the carb'd cars, no pump, no pressure. So is it possible that there is a siphon effect pulling fuel back into the tank when the fuel pump isn't running? The return line being lower than the supply and slowly pulling fuel past the check valves in the fuel pump? Just a WA theory... It's can't be so hot that you're simply percolating (boiling) the fuel in the carbs and lines. Could it?

FastWoman is the guru who coined the ECU drift concept. In theory, if the electronics in the ECU drift over time, then you could end up running either rich or lean, but in FastWoman's case, she ended up lean. Here's the two main threads of the saga: http://www.classiczcars.com/forums/showthread.php?40234-Purs-like-a-kitten http://www.classiczcars.com/forums/showthread.php?42429-Update-on-EFI-mod-potentiometer-on-coolant-temp-sensor-circuit I don't know if there are any differences in AFM's over the years.

Yes, I'm saying that you use a short piece of tubing to connect a small funnel directly to the input nipple on the carb float bowl, and then slowly pour gas into the funnel until the carb won't take any more. Then after the bowl is as full as it's gonna get, do the same thing to the other carb. After you're done with both, set the funnel and short tube aside and connect up the fuel lines from the fuel rail and then try to start the car. If everything is working properly, the fuel in the carbs bowls should be enough to run the engine for at least thirty seconds or more before they need more fuel, and by that time, hopefully the fuel pump is on-line and pumping it's little heart out. Your question about "do I need those emissions devices?" is a little tougher to answer. It all comes down to what you mean by "need". All of the emissions devices on your car were put there for a reason. That reason is to make the world a cleaner, greener, better place for all those who walk this earth after you. Your car would probably run smoother and perform stronger without any of them in place, so if you look at it that way, you don't really need any of them. However, if you care about doing your own little part to preserve what's left of the environment, then you should try your best to comply. Some systems on the car do not cost anything in the way of performance yet do have environmental benefits: The PCV system The evaporative emissions system The throttle opener system And then there are some systems that do potentially cost performance: The EGR system The AIR (Air Injection Reaction) system (the air pump) All depends on where you stand and that part is up to you...

Ummm. I was kidding? Haha!! Have you seen any of my work? I live for that kind of stuff! :laugh:

Bummer. :hurt: I know you're beat up and I hope they can help you get to the bottom of the issue. Reputation is that if there's something wrong with the carbs, they're the guys, right? I just can't imagine what could possibly be wrong with the carbs themselves. Cracked body somewhere? Wrong springs installed somehow? Wrong needles installed somehow? Wrong suction pistons installed somehow? One last question before we all wait to hear back from ZT... Did they always have that lean mid-range from day one when you got them from ZT, or is this something that developed over time? Anyway, good luck to you and ZT!!

What? You mean way over-engineer a solution and spend ten times what normal people would consider a "reasonable" amount of time on it? In the end, it works great and looks cool, but it took way too much labor to make and nobody in their right mind would ever pay what it should really cost. Now you've got my attention!!

I've got some GM locks disassembled as well. That sidebar is pretty effective. Definitely a step up in security compared to the original Z locks. If I get a chance, maybe I'll snap a pic or two of the GM stuff... Haha. That's exactly what I did with mine until I get around to fixing it right.

Thanks Willoughby! I guess I should have thought of looking at the parts manual. Thanks for checking!

If it is a lean condition, I'm not sure that it ever does go away. I was theorizing that it isn't as noticeable once the engine is warm. It may still be lean even once warm, but just not enough to cause a drivability issue. And I know that you know... There are plenty of other ways to run lean other than by having a vacuum leak. AFM problem. Throttle position sensor problem. Coolant temp sensor problem. Intake air temp sensor problem. Fuel pressure problem. Fuel filter clogged. Injector(s) clogged. ECU drift problem. And probably others that the experts can come up with! And not to forget... Any air leak anywhere between the AFM and the pistons. On either side of the throttle butterfly is a problem. Basically, if it doesn't go through the AFM, the ECU won't account for it. (Yes... I meant intake to head. I've clearly got a lot to learn!) :stupid:

Yeah, that's what I figured. I do know from experience that the "inside the distributor cap" GM HEI modules were subject to heat related failures. You are supposed to use heat sink compound (thermally conductive goo) on the underside of those modules to help conduct the heat away from the module. That, and there was a little breather filter screen in the bottom plate of the distributor that would corrode and clog. Once it was clogged, the temps went up. I'm sure mounted on a fender wall, they would be fine.

I'm now (thanks to Blue) intimately familiar with the inner workings of the AAR, and I don't think that's where your problem is. I'm new to the details of the FI stuff, but here's my theory... From the instant you start the car, you are running lean. When the engine is warm, it doesn't matter as much because the warm engine is more tolerant to a lean condition. But while the engine is cold, it's less tolerant of the lean condition and it causes your idle issues. I'm thinking that it's so lean that even a cold (open) AAR isn't enough to bring the idle up to the 1200-1400 that you would expect on a cold start. Your foot on the pedal for thirty seconds FORCING a high idle is long enough to shake the cobwebs out and raise the engine temperature just enough that the AAR can now succeed and continue to hold the idle up where it should be. That's why blipping the throttle while cold doesn't do much, but holding the RPM's up at 2000 for thirty seconds does. I think you nailed it back in post #55 when you compared it to carbs where you "had to throttle it up a little just long enough to get it past it's "coldness" so to speak so it would idle on it's own?" I think that's exactly what's going on. Your mixture is off and your engine is really struggling when cold. Have you checked for vacuum leaks? I'm thinking something like maybe the intake manifold to block connection. Severity of the leak may even reduce some as the block heats up...