Captain Obvious

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...

I remember reading the same thing. I read it on the web so it was of questionable validity, but I do remember hearing that. But on the other hand, I've had GM V-6's in the past that used their HEI modules. I had no ignition issues that I was aware of and I easily reached 6500 RPM. Anyone have any thoughts on the matter?

Still wondering if my 77 is supposed to have a fan shroud. Anyone know if it only coming with A/C cars applies to all years?

I think those two tubes you show in the last two pics connect to your flow guide valve. It's an early crude evaporative emissions control system who's purpose is to capturing and store the fuel vapors that evaporate out of the gas tank when the car is not running. It's the predecessor to the carbon canister containment systems that are on newer vehicles. Plenty of details in the fatory service manuals. By the way, I know you've got an L28, and I know you are pulling off flat tops and replacing them with round tops, but what year is the car?? With flat tops and a flow guide valve... I'm guessing it's a 73? If it's a 73, then you can find info on the flow guide valve on page EF-20 in the Engine Fuel section. As for starting it... When you get to that point, you could just crank it and (hopefully) go, but sometimes it can be a pain to get enough fuel to the carbs to get it to catch in the first place. I would recommend filling the carb float bowls with a funnel and short piece of tubing first, before you connect up the real fuel lines to the carbs. That way you shouldn't have to count on the fuel pump until after the car is running. But before you bother even putting the carbs on the car... Have you checked your round top float levels?

Looking forward to the pics. What was the cost, if you don't mind me asking?

Does that hold true for all years? My non-A/C 77 doesn't have a shroud either and I assumed it was tossed by a previous owner.

Well my first foray into the junkyards was unsuccessful... Nissan changed their lock designs to a double sided tumbler design* sometime before 1986 and made the tumblers wider as part of that change. The new ones won't fit earlier locks: I don't know when they made the change, but the oldest Nissan I could find in my local U-Pull was a 1986 pickup. Apparently not old enough. *The new design uses both sides of the key at the same time. Our keys are cut on both sides, but that's for convenience only so you can put the key into the lock and it will work either way. On the early Z locks, you could theoretically get your key cut on just one side only and it would still work if you inserted it the right way. The difference is that on the newer designs, half the tumblers are actuated by one side of the key, and the other half are actuated by the other side of the key at the same time. Not that it matters, but I think it's a better design because the forces of the tumbler springs being on both sides of the key will help keep the key centered in the lock, unlike what we have where all the tumbler springs always push the key in the same direction. The new design has got to be better for minimizing wear inside the cylinder plug.

Pictures worth 1000 words?

Do you have copies of the service manual(s)? You need two copies... One from 74 and one from 72. The 74 will help identifying the hoses from the flat-tops, and the 72 will help identify what you need once you're done. The manuals aren't perfect and there will still be questions, but they will help a lot. OK, Here's your first pic. The two hoses that come off the original flat top balance tube... The larger one should be for your brake power booster, and the smaller one should be the vacuum source for your heater system. If you want power brakes and a heater that works, you're going to need to figure out a way to get vacuum to both of those hoses. Your second pic... A little blurry and tough to figure out what you're identifying, but I'll give it a shot. Going clockwise starting in the upper right. a) Brake booster - You need this. Coolant out of rear flat top returning to water pump - Pull the hose and cap it off near the firewall. c) Coolant supplied from thermostat housing into front flat top - Pull the hose and cap it off at the thermostat housing. d) Bundle of snakes identified with star - Can't tell. Need a better pic. e) Two fittings on front intake manifold - F = Throttle opener system, R = anti-backfire valve system. f) The smaller starred circle - Can't tell. Again, need a better pic. The red and yellow fittings you have capped off in this pic are for the throttle opener system. It's function is to reduce emissions by opening the throttle a little under very high manifold vacuum. There are some good pictures of that system in the FSM. Look there first and after that, if you still have questions, come back and ask. On your last pic, the tube in question is coolant supply to the balance tube. Coolant is supplied to the tube you have identified, flows through the balance tube under the EGR valve, and then returns back to the engine through the cut off tube sticking out the bottom in your pic. Study your service manuals.

Here's the thread that Bruce was talking about. It's not that detailed as far as exactly what to do with the hoses, but it does give a good mechanical overview. http://www.classiczcars.com/forums/showthread.php?44969-Flat-top-carbs-replaced-with-ZTherapy-round-tops I'll get to the details of your hoses in a second. I have to open up your pictures first...