FastWoman

Removing a working AAR will result in the loss of high idle when you first start the engine. Normally the engine will idle at about 1500 RPM and then slowly drop over the next min or two to maybe 800 RPM. Without the AAR, you'll run roughly at maybe 650 RPM when you first start, and then the idle will slowly increase to about 800 RPM. And yes, when you remove the CSV, you'll have a harder time starting the engine below 50 deg F. (It's not active at higher temps.) The two types of ECUs: As far as I'm aware, the ECUs are roughly compatible, but Lenny would have much better info on that issue. I believe there are also a lot of unused pins on each of the years, so if you're seeing the connector completely populated with pins, I would bet there are no wires attached to some of them. Oh, and deciding not to sell her: Good news!

Your final note is interesting, namely that two different ECUs run differently. That attests to drift of some sort, even in the earlier Bosch ECUs. My two '78 Hitachi ECUs run exactly the same -- too lean, without modification of the CTS resistance.

Might be that a good whack is all the stupid thing needs!

I drove a '75 Z back in the 1980's. It developed a rust hole in the siphon tube inside the tank, so that when it got down to a half tank of gas, the pump would be drawing air. A more common problem is that rust and debris can clog the intake screen as it sloshes around inside the tank. Then when you shut the pump down, the debris falls to the bottom again.

Very nice looking, Lenny!

Funny this thread popped up again today! I finally dug out my old inspection light from a box last night. I had ordered a couple of Chas' lovely lenses and wanted to test the fit. His workmanship is beautiful, and the fit is perfect! I'm in awe of his talent. As for the source for new inspection lights linked by Dr. 240Z, up around post #13... Well, I have that site bookmarked as "New Z parts -- Last Resort Shyster," so beware. The guy often GROSSLY overcharges, and he doesn't take returns. He charged me a mint for some part I found in abundance on ebay about a week later for 1/10 the price (new, genuine Nissan, in the Nissan-labeled Nissan bags). When I approached him about it, his attitude was essentially to go and f*** myself. So buyer beware!

Lenny, I had asked this before, but I don't think you had addressed it yet: Is your Hellfire going to have IACV capabilities? It would take a bit of cobbling to make a stand-alone IACV, but it could certainly be plumbed in place of the fussy old AAR, which I would dearly love to remove from my engine and beat to death with a sledge hammer. (OK, I wouldn't really do that. I'd actually pack it away lovingly in a box.) I don't know whether there would be enough free lines on the ECU connector to do that, but I certainly wouldn't mind there being an extra connector on the box for additional, non-OEM equipment (e.g. O2 sensor, IACV, ignition equipment, A/C clutch input for bumping idle, ???). Anyway, I would LOVE to have an ECU controlled IACV, instead of all of the current Rube Goldbergery -- AAR, BCDD, and vacuum-solenoid-A/C-throttle-bumping thingie -- none of which works very well.

Great news, Lenny! Please check your PM inbox.

"In the software setup for each sensor, there is a field to select an ECU pin number. If you tell the software that the AFM is attached to pin X instead of pin Y, it doesn't care how crazy your wiring scheme is, it will just read pin X and run with it." NICE!

My HEI retrofit has been in service for a pretty long time now, with no issues. I highly recommend it. For those 280Z owners reading this thread, I'll mention that the MSD 6AL is incompatible with the 280Z's ECU. You'll end up with plenty of spark, but also fuel problems. It's no problem for the 240 or 260.

Tomo, Pomorza (Jan) posted this photo of his megasquirt setup, which would have the same MAP sensor as one possible configuration of Lenny's system: https://fbcdn-sphotos-e-a.akamaihd.net/hphotos-ak-ash3/527276_10152006457680347_412958556_n.jpg The beauty of these systems (either MS or Hellfire) is that they're configurable for what you have and what you need. The Hellfire can work as a P&P ECU with stock components (including the AFM) if you wish. Or it can be configured more like Jan's MS system with the MAP sensor. Or I *think* it can even be configured with a hot-wire MAF sensor, which would go in place of the AFM and would be maybe 1/4 the size. If I understand the MAP sensor strategy correctly, it can be done with a small vacuum line running from the intake manifold to a MAP sensor placed on the circuitry board of the ECU. Or there can be a MAP sensor attached directly to the intake manifold, with wiring running to the ECU. (Right, Lenny?)

Costjo, all your plugs are too lean, except for 2 and 3, which might be WAY too lean. Once the mixture leans out enough, the cylinder starts to partially misfire, which can make the plugs look as though the mixture is too rich. You might have a vacuum leak that bleeds air to #2 and #3, for instance if your intake manifold isn't seated well.

Kudos to you, braving the weather like that! Have fun. We'll be thinking of ya'.

Definitely calibrate the AFM! That may be it. However... Here's a somewhat esoteric bandaid approach that I've never seen tried: If all else fails -- if all your EFI components (except the ECU) are all good, if there are no leaks, your valves are in adjustment, engine is timed correctly, distributor advance isn't sticking, and you STILL have a rich condition (just like the '78s tend to have that lingering lean condition), then you might consider the following adjustment to the CTS circuit: See if there's some way to accommodate an additional CTS sensor in the thermostat housing. There may be other years, or perhaps California versions, that have additional bungs that would allow you to screw in another sensor. Or maybe there's some other temp sensor for a different vehicle that has a lower resistance that you can substitute for the one you have. (You'll have to get creative here.) Then wire the two CTS sensors in parallel. That would give you half the resistance, while still being responsive to temperature changes. This would lean the mixture. As the mixture might end up being too lean, you could then richen it slightly (to fine-tune it) with a potentiometer in series. Or.... Keep your eyes on the ZFuel thread. The cavalry might be coming to our rescue right now. Soon we'll have the ability to toss our deteriorated ECUs and get our engines running straight with whatever components we have installed. I think that's the ultimate fix.

Mike, it's really very difficult to explain why, but almost every electronic control system is ultimately voltage based, even if it seems to be resistance based. The AFM itself has both input and output voltages, and it's the output voltage that the ECU monitors. It doesn't really care about resistance, except for the air temp sensor, I suppose. The CTS, on the other hand, has a resistance, but that resistance is only meaningful when you send current through it and measure the voltage drop across it, which is what the ECU does. So the way the AFM, if you were to change all the resistances in the AFM by 12-15% (excluding the air temp sensor, which works like the CTS), the output voltage would not be changed. However, if you were to do the same with the CTS, the current/voltage relationship would be changed, and the ECU would respond differently. That's oversimplified, BTW. - - - Updated - - - Mike, it's really very difficult to explain why, but almost every electronic control system is ultimately voltage based, even if it seems to be resistance based. The AFM itself has both input and output voltages, and it's the output voltage that the ECU monitors. It doesn't really care about resistance, except for the air temp sensor, I suppose. The CTS, on the other hand, has a resistance, but that resistance is only meaningful when you send current through it and measure the voltage drop across it, which is what the ECU does. So the way the AFM, if you were to change all the resistances in the AFM by 12-15% (excluding the air temp sensor, which works like the CTS), the output voltage would not be changed. However, if you were to do the same with the CTS, the current/voltage relationship would be changed, and the ECU would respond differently. That's oversimplified, BTW.

AWESOME! TOTALLY AWESOME! Thanks, Lenny! You made my evening!

Maybe you can measure duty cycle with a dwell angle meter wired between +12 and the output of the ECU (note: not the contacts on the injector, which would have a lower voltage differential across them. The answers to your other questions all "depend" on other things: Would a pot on the CTS make up for an out-of-spec AFM? It depends on how it's out of spec and how the pot is wired. Not enough info here. Would turning the pot CCW...? It depends on how the pot is wired. Adjusting it to a higher resistance gives you a richer mix. You can determine which direction raises resistance with your multimeter. Your resistances aren't "awfully" out of spec. However, there's much more to a properly operating AFM than just those resistances. The ECU actually looks at the output voltage. The pot inside the AFM acts as a voltage divider. So if ALL your resistances were 10% high, it would make no difference at all.

Captain, I think this was the first successful implementation of a digital ECU designed specifically for the 280Z. So it actually was a first -- much more exciting than even the Super Bowl, IMO. Disclaimer: OK, I'm not a football person...

IT LIVES!!!! Congrats, Lenny! This is all very exciting! I'm wishing you some decent weather, so that you can continue troubleshooting. And congratulations on your expected arrival in April! Woohoo! It's all wonderful news! And I forgive you for not having the video. Maybe you give us the video on the second start, when you have the MAP hooked up (or are running in the AFM mode) and are starting it for real. Yes?

And me. A g-nose is beautiful, but it just doesn't look like a Z to me -- that same car that I envied in high school and one of the few machines that defined a generation. And unpopular though it may be, I'll take mine with the big, projecting front bumper!

Chris, I simply like big electrical contacts for high current. I wouldn't completely trust the contacts on a small fuse not to overheat when carrying 30A, even if the fuse is rated 30A. I'd anticipate the possibility of arcing, melted plastic, and other mischief. (Even our 1/4" glass fuses sometimes get pretty hot!) I would trust 20A, because I've seen enough 20A fuses of that size that I know they're OK That's just my gut feeling. To put it in household wiring terms, I just finished installing 150A electrical service to a workshop. The massive branch breaker that goes in the main panel occupies FOUR breaker slots, because TWO slots would be inadequate. As I look at the amount of metal making contact, I would say each slot has four times the metal one would find in one of those standard sized automotive fuse tabs. Not only that, but there's a special compression spring on each pre-greased contact! That would be 8x them metal overall for a 150A circuit. Divide 150 by 8, and you fall in the range of that 20A fuse I would trust. FAIW, I did once run a 30A fuse of that size. It had to go in a tiny space on the upper kick wall of my '66 Mustang, in the accessory block I rigged for my stereo system. When I had a VintageAire A/C system installed, the installer covered over the fuse block with a duct. (I wasn't happy about a few aspects of that installation.) To make a long story short, the contacts on that 30A fuse were really inadequate, and the circuit kept going out, requiring me to unfasten the duct, so that I could reseat the fuse. Very annoying. Now it wasn't a great fuse block -- not as nice as the Blue Sea -- but still the contact was inadequate at 30A. But like I say, running two 15A fuses in parallel would work fine. An overcurrent would blow both fuses. I think a single 20A fuse is also fine for that size of fuse, but 30A seems to me a bit much (even though I realize you can do it).

I rewired my boat in 2005, using a Blue Sea block. We sold the boat a few years ago, and the block was still in like new condition. This is remarkable, considering the salt air and the really high humidity here. I think that part held up better than any other metal part I've installed on a boat (stainless?). If it can survive there, it should survive very well under the hood. I got mine at West Marine, BTW. That said, a 30A circuit might do better with a Maxi Fuse. Or you could always wire two 15A fuses in parallel. Use silicone dielectric grease on the contacts! BTW, I wouldn't trust the snap-on shield not to snap-off and fall onto the roadway at some time. Perhaps there's some way to secure it with screws. Or you could always just do without it.

Just look at where the flap comes to rest. As I recall, the '75 AFM has no bumpers to stop the travel of the vane, but it's rather obvious looking at it where the vane is supposed to stop when fully closed. If it's somewhat curved and rests past that point (mine was bent maybe 1/4" past), then it's bent. As I recall, I cut a block of wood to stick up through the throat of the AFM as an anvil, and I tapped a block of wood on the other side to straighten the flap. All I did was to straighten the curve. My engine instantly ran better. There's also the possibility that your AFM's clock spring has been adjusted by a well-meaning mechanic. Visit the Atlantic Z website for a re-calibration procedure. And it's also possible a well-meaning mechanic wrapped up a fixed resistor in your fuel injection harness. Such was the case with mine. I removed mine and ultimately inserted a variable resistor (potentiometer) to tune the mixture. **Is it possible the ECU could be at fault on the rich running?** Yes and no. The ECU drift issue seems to plague the later models (77 and especially 78). I believe Datsun made a shift from Bosch (your year) to Hitachi (my year) somewhere along the line. The ECUs would have been functionally similar, but with somewhat different circuit designs. In the '77/78, there seems to be a pattern of drift towards the lean side. This would represent a common failure mode characteristic of the design. Could a '77/78 ECU drift the other way? Not likely. It would be more likely that the unit took some sort of damage to cause it to suddenly run rich. None of this is to say how a '75 Bosch ECU might drift. Frankly I wouldn't have a clue. I've not heard of the '75 ECU drifting, but that doesn't mean it doesn't happen. It's possible. Time and heat are the enemies of electronic circuits, and 40 years (almost) is quite a long time for these circuits to keep running within spec. I would be astonished if the circuits in your ECU hadn't drifted. The trick is whether the designers were clever enough to design in compensations to keep the behavior of the ECU relatively stable, despite the drifting of individual components.

Bart, it's interesting that here in Virginia I have the option of self-certifying my own antique vehicle safe. I think the rationale is that modern mechanics don't know antique vehicles the way their owners and restorers do. My inspection standards are much higher than the state's anyway. However, I don't take this option. Every year I go to the inspection station, and the kid who KNOWS my vehicles are in top shape always practically waves me through. He'll sometimes put my car up on the lift, so I take the opportunity to walk around the underside and do my own quick inspection. The reason I pay my $16 is that I have had my vehicle certified "safe" to state standards by a professional safety inspector. Then if I get into an accident, and someone decides to sue me, I can show I've taken reasonable steps to maintain my vehicle in safe operating condition. In our litigious society, I think that's $16 well spent!

Other rich-running causes, besides the CTS and FPR: Cold start valve. (Test by clamping or blocking the fuel line.) It might be stuck open, or the thermotime switch might be bad. Or perhaps something was miswired. Bent AFM vane (from backfire). I had this issue in a '75 (which doesn't have the backfire valve). A backfire bent the vane, so that when it opened, it turned the potentiometer a bit further than it should have. I fixed the issue literally by tapping the vane out with a hammer. AFM broken, misadjusted or out of specification. As far as I'm aware, any other problem would cause the engine to run leaner, not richer.