FastWoman

Zed, the transistor is actually more like a switch or a relay than a resistor. It would almost be as though the ECU had a wire from the injector that it would periodically short to ground. When the wire is shorted to ground, current flows from the battery, through the maxifuse, through the fuel injection relay, through the drop resistor, through the injector, to ground. This current opens the injector. When the short to ground is broken, the current stops, and the injector closes. Without some component(s) to pull the voltage up to +12 (which could be via the injector, if plugged in), the voltage on that "floating" connection to the injector will fall towards ground because of current leakage inherent in the transistor. Of course there could be such components in the ECU for some purpose.

Oh, and your second question to ZH: You plug the bulb (do you have one?) into both sides of the injector connector to make it flash. However, to test for voltage to the injectors, you would connect the black lead of your multimeter to ground and the other lead to either of the injector plug contacts. (One should be +12, and the other should not -- with the injector unplugged, that is.)

One more thing: Just so you know how the injectors work... The ignition relay actuates the fuel injection relay. The fuel injection relay feeds +12 power to the drop resistors and the ECU. The drop resistors feed +12 power to the injectors. The other side of each injector runs to the ECU. I'll call this the "floating side" because it floats electrically. Between injection pulses, the floating side is... er... allowed to float at whatever voltage it likes, almost as though it weren't connected to anything. So it will float at 12V. You'll see the same voltage on each side of the injector. (Don't go "Aha!" here. This is only true because the low resistances of the injector and the drop resistor drag the voltage up to 12V. When you unplug the injector and insert a very high resistance multimeter in its place, the voltage could be almost anywhere.) When the ECU pulses the injectors, it does so by "grounding" the floating wire by creating current flow through a transistor to ground. The actual voltage will be a fraction of a volt off of ground. And that's basically it.

OK, good! Here's what we've learned: When you put the digital voltmeter to the injector connector, if you had power you'd have probably gotten SOME reading. I'm not sure what it would be, though. One lead would be at +12 (the one leading to the drop resistor assembly, which is then fed by the fuel injection relay, which is fed by one of your maxifuses, which is fed by the battery. The other lead would likely be at some fraction of a volt, but it wouldn't be a stable or meaningful voltage, and when you reconnected the injector, the voltage should have been dragged up to 12V, except whenever the ECU would pulse it. It would have been better to test for +12, referenced to ground, at each of the injectors and at the #10 pin of the ECU connector. (There is a diagram on p. EF24 of the FSM that shows you the pin layout, and there are little numbers stamped into the connector itself.) Anyway, the fact that you read NOTHING (0 volts, right?) probably indicates no power from the fuel injection relay. And I say "probably." It would have been more meaningful to do your tests at the scary ECU connector with so many teeth! Trust me that you're not going to hurt anything by unplugging the thing and probing it. After you unplug the ECU, there are no sensitive electronics left. It's all sensors, switches, servos, power supply, etc. The only sensitive thing has been unplugged. Incidentally, the two LEDs back to back is a good approach. But also insert a 1000 Ohm resistor in series with them, so that you don't blow the one LED that's wired in the correct direction! Anyway, I think you found your smoking gun. It's something in the relays you moved under the dash. There are two relays of interest here: the ignition relay, which feeds power to the coil on the fuel injection relay to actuate it, and the fuel injection relay. You might have either a bad relay or a bad connection to the relay. Just be aware that parts, especially electrical ones, do not necessarily fail completely. They often fail intermittently. Your problem is (or was) intermittent, so that's the sort of problem you're looking for. I'd pay special attention to the condition of the connectors plugging into the relays. The metal could have weakened or become corroded. And remember that the wires are crimped into those connectors. You could have a corroded wire or a bad crimp. Examine them carefully. If I were you, I think I'd try recreating the problem with the old relay in place and the ECU unplugged. Turn the ignition on, and measure pin 10 to see if you have voltage. Then with the ignition still on, start GENTLY wiggling the relay wires and connectors to see whether you can make any of them click. If you can, then you're "exercising" your intermittent connection problem. Then substitute the new relay and see if you can recreate the same clicking. If not, then it's probably a bad relay. If you can, then it's a connector issue. Keep hunting and poking, and you'll find it. And after you think you've found the problem, still don't stray too far from home, and carry spare parts. This car can't be your DD YET, and you absolutely should not take your daughter anywhere in it (as you don't need the negative energy right now). After you've driven the car for a while with no issues, you'll be able to certify it "reliable" and use it as your DD. And FAIW, the more you drive the car, the more reliable it will become, just due to use. Nothing ails the electrical system of a car like sitting. A car needs to be driven. You're going through what I call the "clearing cobwebs" period.

Rossiz, Your Z will eventually become reliable if you keep picking at it. Be brave. Don't listen to your daughter and/or any other naysayers. The best news, although it doesn't sound like it, is that your intermittent problem has become consistent. And where there's a consistent malfunction, you have some hope of diagnosing it. OK, you say you're getting no voltage to the injectors. That could be a MAJOR clue. But before we conclude that's the case, we need to be certain that's what's happening. You tested two ways. The first way was with a voltmeter. Was it an analog-type voltmeter, with a mechanical needle, or was it electronic? And EXACTLY what did you find? Then you tested with an LED across the leads. Depending on how you hooked it up, it either wouldn't have worked, or your LED could have been destroyed unless you had maybe a 1 kOhm drop resistor in series. The best test is with a miniature Christmas light bulb, such as you would pull from a long string that you would hang on your tree. You should see it flashing dimly and slowly (once per revolution) as you crank the engine. If you pull the connector off of the coolant temp sensor (the sensor with the connector like the ones on the injectors), the light should flash more brightly. The tests laid out in the FSM are pretty straight forward. You SHOULD be able to find pin 37 (or whatever pin) on the ECU connector. They're numbered on the connector and are in order. By testing the injectors one by one at the ECU connector, in the manner described in the FSM, you should be able to diagnose the injectors, the drop resistors (located beneath the brake master cylinder) AND their wiring at the same time. Until you do these tests in a methodical manner, there's nothing any of us can do except to guess. So if you truly love this beautiful machine, you're going to have to fight for her! FAIW, my GUESS, and it's only a guess at this point, is that you don't have power to either your ECU or your injector drop resistors. (How do your fusible links look? Crusty and awful?) Or perhaps the ECU is not adequately grounded. Less likely, perhaps your ECU is bad. Oh, I'll mention we have four cars -- a '92 Saturn SL2, a '94 Mazda Miata, an '09 Dodge Ram, and the '78 Z. They are all very reliable vehicles, because I keep them well maintained. It might surprise you to learn that we consider all of these vehicles approximately as reliable. Whenever we hit the road to Richmond (about 1.5 hr), we take the Z, feeling it's safer than the Miata and more fuel efficient than the Dodge. It also has working A/C, unlike the Saturn. And of course it's fun to drive. BUT... There were a couple of times, before I finished straightening out the Z, that it had to be towed home in humiliation. And there were times I had a HELL of a time getting her started. But not anymore. All fixed.

Congrats! Sorry I wasn't here for you yesterday, but it looks like everyone else got you running! I hope you had a great victory cruise. Whenever conquering a problem, don't forget to do the ritual snoopy dance around your car!

Hey, congratulations, Len! Another new life embarks on her own journey! Way cool!

I used the "test your server" link that Pat cites above -- a utility written by an Italian programmer. Here's the result for classiczcars.com: Test your server for Heartbleed (CVE-2014-0160)

Hi all, Today I've been checking websites where I have logins for their vulnerability to the heartbleed bug. Most sites have been checking out alright. However, classiczcars.com apparently has this vulnerability. I don't yet know the full implications of this security threat or how the security threat would be corrected, but I thought I should make my fellow Z enthusiasts aware of the problem. Peace, Sarah

Running the fuel pump will cool the "trumpet," and the legs leading to the injectors might also fill with fuel, but the injectors will still be hot. Actuating the cold start valve wouldn't cool anything down, any more than running the pump (which would do much more good), but it might spray enough fuel to run the motor. That would be a very fiddly way to start the motor, but it might work. Rossiz, for the sake of this thread... Yes, you indeed had a hot restart issue. What is the configuration of your engine?

Yes, it's (much) too lean, at least at idle. First thing to check: Throttle position sensor. See the FSM. Next, check for vacuum leaks, and make certain every other fuel component is working properly. Check timing, valve lash, etc. Calibrate the AFM clock spring per Atlantic Z. If you've ruled everything else out and still have a lean running problem.... Yes, you want to add the potentiometer to richen the mixture. You don't want to richen the mixture with adjustments to the clock spring, because that will leave you with a leaned-out engine at WOT. Zed is correct that there's a separate idle mixture screw. However, in MY experience (not to say other people would experience this), it doesn't really do much. I have mine adjusted 5 full turns open (CCW) from fully closed. This is an arbitrary position, but it allows at least some flow-through in the event of a backfire. Anyway, with my idle mixture screw adjusted 5 turns open and my AFM calibrated per Atlantic Z, I've found my mixture under load is approximately correct when my idle mixture is correct (adjusted slightly to the rich side of the peak RPM / vacuum). I judge my mixture under load entirely by the "feel" of the engine and my reading of the plugs, currently lacking any more sophisticated method. But plug readings are a pretty good indicator.

Well, you could always take the time-honored approach of asking, "What's the least you would take for this car?" Or, "How firm are you on that price? It seems a bit high for a car that's not running." Oh, and... errhem!... about the 280 not being as valuable as a 240 thing... OK, it's true. But it's not dramatically true. A 280 can be valuable too. However, unless you're a flipper or a collector, that doesn't really matter. If you're buying the car to enjoy, buy the car you like. I suppose if you're buying a $1000 240 vs. a $1000 280, you might get more for your restoration dollar when you sell the 240, assuming it's kept 100% stock, is a low number, has matching S/N engine, etc. However, if you start with a running car that's in halfway decent shape (which I would recommend), you will get into the 280 for less money and get out of it with less money. And you will have cheaper fun with less at risk -- and quite likely a car that's nicer to drive, depending on what you want from the car. All I'm saying is that there's no "wrong" choice, despite what some 240 owners might think.

I'm not understanding, Mike. When you open the AFM vane very slightly (maybe 1 mm), what happens? RPM increases (indicating your engine runs too lean)? RPM decreases (indicating your engine runs too rich)? Not much (meaning your engine runs with about the right mix)? Note: I'm not talking about adjusting the clock spring. Rather, I'm talking about pushing the vane slightly farther open than it "wants" to be.

Andrew, it's perhaps an occupational hazard (former neurobiologist), but I can't think of the "screwdriver to the ear test" without thinking of Phineas Gage: Phineas Gage - Wikipedia, the free encyclopedia My son told me over the phone about the old screwdriver trick, and I immediately ordered him a mechanic's stethoscope, which works a TON better than a screwdriver and is also safer -- and probably even cheaper. Harbor Freight -- best few dollars you'll ever spend on a tool!

"bronze bushing upgrade" Yeah, I have that too, but I don't know whether I'd call it an upgrade. The shifter is really nice and tight, but that RATTLE/BUZZ is really annoying. Anyway, I wouldn't be afraid of that noise. It doesn't really signify anything, except that maybe the nylon bushings are a more civilized choice.

Mike, I suppose I never noticed whether my carbon deposits (both plugs and tailpipe) were fluffy vs. harder. However, I am 100% certain they were from an extremely lean condition. When I richened the mix, the engine ran much, MUCH better/stronger, and the carbon deposit issue went away. My plugs are now a pretty mocha. I, too, calibrated the AFM per Atlantic Z, and my CTS was functioning in spec. All electrical connections were new, injectors new, all other components individually cleaned/verified or replaced if needed, rebuilt distributor and correct timing, properly adjusted valve lash, everything verified to OEM specs, zero vacuum leaks (new tubing, accordion boots, intake/exhaust manifold gasket) -- and VERY lean running. The problem was the ECU, which had drifted lean. The fix at that point was the potentiometer. My Z is a '78 with a Hitachi ECU. If your '75 has the original ECU, it's probably a Bosch. I think it's the '78 (and '77?) Hitachi ECUs that have the biggest lean drift issue, but maybe also the Bosch. Check to see what mixture your engine "likes" by fingering the AFM counterweight while your engine is running. If the engine runs at a higher RPM and better vacuum when you open up the AFM a tiny bit, it's running lean. Easy test. Ideally, your RPMs should drop off in either direction, whether you finger the AFM richer or leaner. In fact you should be just a tiny bit towards the rich direction. As for the altitude question: According to the FSM, you should inject about 6% less fuel above 3675 ft vs. below. Up at 9000 ft, you might need an even leaner mix still. (I know that I lean a lot when walking around at that altitude!)

Mjr45, FAIW, an extremely lean condition can result in carbon fouling because of incomplete combustion.

I remember having a worn lower ball joint in a Datsun 210. Everything would be fine until I reached about 55 mph. Then I'd suddenly get a violent shimmy. A mechanic found the problem after wrestling with my front suspension for about 15 min. As I recall, it took a crowbar to pry the part enough to reveal the play.

BTW, I note that JRSGTS (on this list) is a pro mechanic specializing in classic cars, located in Greenwich, NY, about 3 hr from you. I realize that's a bit of a hike, and I suspect you can tackle this issue on your own. However, he's there if you need him. He's not a Z specialist, but he's currently working on a customer's Z and is coming up to speed quickly -- apparently eager to learn. There may be other mechanics closer to you who would be willing/able to work on your Z. In fact you might find some old-timer mechanics at your local Nissan dealer. The PO of my Z lived in a fairly remote part of Virginia, but he was able to find expertise at the local dealership. There was one mechanic there who cut his teeth long ago on the Z and did all his work. I've had a few nice conversations with him, both before and after the sale. I vaguely remember being at another Nissan dealer's service department inquiring about a fuel pump check valve. One older mechanic shouted over to another and asked, "What's the part number on those old Bosch check valves?" The other mechanic rattled off the number from memory! I mention all this not because I don't think you're up to solving this fuel delivery problem. I think you are. Rather, I saw JR's post on another thread and remembered you -- both of you from the nether-regions of New York.

If you have the pump off the car, pre-fill it with gasoline. Just pour the gas right into the holes until it won't hold any more. That was enough at least for my new pump, even with air in the new intake line. Another approach might be to use a mighty-vac in the engine compartment to draw gas from the tank into the pump.

Leonard, ahhhh, geee.... I've never heard of such a thing happening! I don't know enough about the heavy mechanicals to venture a guess, except that it sounds like something fell apart, rather than broke. Was it making any noises before all hell broke out? Depending on the condition of the entire car, it might be worth trying to repair the block, if that's possible. I've seen skilled welders and machinists do some pretty tricky stuff. It's too bad you don't live in my neighborhood. We have Naval shipyard machinists and welders, both active and retired, all over the place! They'd fix you right up!

My vote would be ignition as well. As long as your jets are clean, it's hard to starve a carbed engine for gas. Floating points are more common. I'd change over to electronic ignition as well, unless it's important to stay 100% OEM.

I don't think you'll hurt the engine, but driving like that on a daily basis can be hell on the rest of the drivetrain. I think the Z can handle it as well as, or better than, most cars, but it's still hell on any car. As to how far you can push without shortening the life? Well, we sent my stepson off to college with an automatic transmission Ford Taurus, which he drove in a very spirited manner -- hard acceleration, hard braking, hard cornering, not slowing for speed bumps, etc. The car is tough, but it came back in somewhat deteriorated condition. My point is that running a car hard will shorten its life. Common sense, really. But that engine is tough, even at 35 years of age!

I don't know about their availability. I suspect you can't get them new (old stock), but there are certainly wrecking yard parts. However, it's not all that difficult to refurbish the things, as I understand, and a refurbished switch would be better than another old switch in considerably used condition. I consider it a karma thing (note the play on words ), but I think there's something wrong with replacing an out-of-production part on a classic car without trying to fix it (or have it fixed). That only contributes to the disappearance of parts and the shortening of the time our cars can be kept on the road. Here's an article for a 240 switch, but I suspect the 280 switch is very similar: Turn Signal Repair | Fiddling With Z Cars The new exhaust should be sweet!

If I were you, I would rule out the pump as Zed suggests. You can "hot-wire" it by running a wire from the battery's (+) post to the (+) post of the fuel pump (blue/green wire). You don't have to disconnect the existing wiring. Before you fire up the pump, connect a long piece of rubber tubing to the "return" line of your fuel rail (coming from the outlet of the fuel pump regulator and sweeping around the front of the engine -- the tube other than the one connected to the fuel filter. Now fire up the pump. Your pressure should be 36 psi, and you should have a steady flow of fuel coming out the end of the hose. You can pour it into a fuel can, or if your hose is long enough, you can dump it right into the filler neck of your gas tank. Just watch it for a while to see what happens. If you've got the same fuel flow and pressure after 15 min or so, then your pump and filters are probably fine, and we search for other issues (like electrical).