FastWoman

A tiny, itsy-bitsy ray of optimism for Blue: There was a time, really long ago, that cheap crap came from Japan. Can China ever manufacture fine products like Japan has done for many decades now? There may be some chance, although I have my doubts whether it's in their culture. Another ray of hope: There was a time, not quite as far back, that the US and Canada actually made stuff -- good stuff. And I think we could do it again in a heartbeat. My little (almost-antique) Saturn SL-2 is a shining example of the brief resurgence of US quality manufacturing. I wonder whether the solution to this fuel filter issue is to place a clear filter after the main filter, so that (1) you can see what's going on, and (2) if the main filter ever craps out, you'll see a big pile of debris in the clear filter. I installed one of these long ago between the tank and pump: http://www.autozone.com/autozone/accessories/Valmar-Marine-Universal-in-line-fuel-filter/_/N-275c?itemIdentifier=294531_0_0_ It seems to flow well enough and hold up well enough. I don't know whether it can hold up to EFI pressures, though. Incidentally, it's built so that you can screw it apart, clear the filter, and reassemble. I think it's constructed of polycarbonate. Thoughts?

Well, you've got... 1. Power to the injectors, which operate when grounded. (Therefore working drop resistors, etc.) 2. Power to the ECU. (Therefore both EFI fusible links and the fusible link relay are good.) 3. Good ECU ground. 4. Likely good connection between ignition coil (-) and pin 1, because tach bounces when cranking, and you have +12 at pin 1 with key on. 5. Fuel pressure 6. Typically pathological priorities at a time when your power is out, your fence has blown down, and your fish are suffocating. Assuming your mechanic was correct that you have no injector pulse (and I'm not totally convinced yet), then it does seem likely the ECU is bad. It will be interesting to see what that '75 ECU does for you.

Very nice job! And you got a good deal on the work!

I agree. And don't go pulling injectors! Pulling injectors can open you up to having to do other stuff -- replacing O rings and insulators, replacing fuel lines, or even mucking with screws rusted in place (like on my engine). There's a much easier way to verify flow if your system holds fuel pressure: Put a fuel pressure gauge somewhere on the fuel rail (or between the filter and the rail). Briefly run the fuel pump to pressurize, stop the fuel pump, and then ground an injector to depressurize. If you don't see the pressure drop when you ground an injector, then you have no flow. Easy.

No problem, Zed! Yes, it's a very easy test. I've never had occasion to use it, but it seems a great way to confirm that the ECU is awake, is being triggered, and is sending out injector pulses. Kelly, if the injectors don't click, then it's either a triggering problem (e.g. wiring to the #1, weak ignition), a problem with the power (which you say you have), the drop resistors and/or injector wiring, or a dead ECU. You can rule out the drop resistors and injector wiring by grounding the individual injectors at the ECU plug. You should be able to make them click. If the injectors do click, then your EFI is functioning, and you have some sort of fuel or fuel/air ratio issue -- bad fuel, clogged injectors, clogged rail, wrong fuel pressure, massive vacuum leaks, or whatever.

I'll just mention that another tool in your diagnostic arsenal could be to unplug the coolant temp sensor (injector-styled connector going to the SMALLER sensor in the thermostat housing). That should result in the delivery of LOTS more fuel, as though you were trying to start the car during the winter in Antarctica. However, try triggering the ECU manually without cranking, the way Zed and I suggested (posts 12 and 39). I bet your ECU is really working.

In general, old/bad gas can be deadly for a flat tappet, OHC, interference engine. If it's bad enough, varnish goo will form on the valve stems, and then it will solidify when the engine cools. When you go to start it again, your valves are stuck in place and collide with the pistons, while your rockers come loose. It makes a delightful, snappy-klink-klink sound. DAMHIK Anyway, I wouldn't do any serious diagnostic work without some known good gas. in the system.

When you ground the injectors via the ECU plug, current has to flow through both the drop resistors and the injectors for you to hear clicking injectors. So if you can ground the ECU contacts and get clicks, you know that... (1) Your injectors have power, I believe through the ECU circuit, (2) Your drop resistors are good. (3) Your injectors are good, at least mechanically. That's not to say that they aren't clogged. (4) Your wiring is good. (5) If the ECU is also operational, then you should get an injector pulse.

You're absolutely certain you have no pulse? Is your noid functioning correctly? It should be a VERY brief flicker once every rotation. If you turn on the ignition with the ECU unplugged, can you ground the individual injectors at the ECU plug and hear them click?

Captain, my faith in automotive manufacturing has been restored. I suggested long ago that there's no way a manufacturer would waste 6 pull-up resistors in the design of a circuit. We had speculated that it might have been just one of those charming '70's things or that the hypothesized pull-up resistors might have been for diagnostic purposes (e.g. to be able to test both sides of an injector plug to confirm power to the ECU). However, a Deutschmark is a Deutschmark (Bosch), or a Yen is a Yen (Hitachi). Anyway, yes, the backfeed through a common transistor connection would explain the +12 on the ECU side of an injector connector without indicating anything about whether the ECU has power. Kelly, if your fusible links are in typical condition, they're probably pretty awful. I, too, would begin my diagnostic efforts with regard to power to the ECU. However (and this is important), I would not start pulling apart the fusible links to do it. Start methodically at the ECU connector to see if you have power. If you don't, then move back to the EFI relay. If you don't have power there, move back to the fusible links. The reason is that if you have a marginal connection somewhere, you can make it good (for the moment), just by jiggling it around. However, sometime when you're out on the highway, it might decide to go bad again, leaving you stranded. Faulty connection gremlins are sometimes very skittish, so to catch them, it's better to diagnose from afar and to sneak in on them -- catching them by surprise before they can clean up their acts. [voice of Elmer Fudd] Be veeeewy veeeewy quiet! I'm hunting gwemlins! Eheheheheheh!

No, you leave the ECU in place. If I recall correctly, the big connector is held down with a screw on one end (??). Free up that one end, and the connector hinges away from the box. It's very quick/easy to get into the thing.

Kelly, I only know of one bad ECU that cropped up on this list. It was a cold solder joint, and it was fixed by re-flowing. So these things are pretty robust. If you do end up needing one, they sometimes show up on ebay relatively cheaply.

Nick, those early analog EFI systems do very well to pass smog, but yes, with a lot of fiddling, they can be made to pass. That said, as familiar as I am with the L-Jet EFI, and as well as I've gotten my engine running in my non-emissions state, I surely wouldn't enjoy keeping my 280 emissions compliant in California! If you prefer EFI and hate carburetors as much as I do, then you can certainly find a '75 280. I would probably replace the 1975 airflow meter (AFM) with a 1976 model, which has a backfire valve in the metering vane. I would also consider stashing away the 1975 hood (if it's original) and using a 1977 or 1978 vented hood, which would help you with hot restart issues resulting from modern ethanol-gasoline. Another option is keeping the '75 un-vented hood and installing a 280ZX injector fan, which will bolt right up. (You'll have to cobble together some control circuitry, though.) There's a fond spot in my heart for the '75, which I bought back in '82 after selling my RX-7. The RX-7 was a cool little car, but the EFI inline 6 of the Z was truly a thing of beauty to this hopeless gearhead. It's been surpassed by generations of advancement, but the flat-tappet head, "bugle" fuel rail, and flappy AFM still make my heart quicken a bit.

Welding... I tried that once! Well, at least I tried. I'm sure it's a learnable skill, just like any other skill. I have nothing to add about the ECU. If it has power, ground, and ignition pulse to #1, then it should be grounding your injectors. If not, then you might have a bad ECU. I'll mention one thing, though: You should be able to fire your ignition manually by connecting a wire to the (-) side of your coil and tapping it to ground somewhere. Every three taps/sparks should get you an injector pulse. It might be easier than cranking your engine. Don't touch the bare wire, because the flyback could give you a jolt.

No problem... Obviously check that the ECU has a good ground also!

Hey Kelly, Good question from Captain! No sparks means no triggering of the ECU. You also need connectivity from the negative side of the coil to the #1 terminal on the ECU to sequence it. You've got 12V at the injectors, which means you've got continuity through the drop resistors. All that's left is for the ECU to ground the injectors. Got power to the ECU, BTW?

My Z stands ready for action! I just finished ticking off a major project, so I think I'll have some time for ECU stuff in weeks to come. Looking forward to it!

Welcome! Sweet ride!

Another option: Put a "tee" in your fuel line between your fuel filter and fuel rail. Then connect the CSV to that "tee," running another line across the front of your engine. That will hold you until you get the correct fuel rail at some future date, or if you don't care about the cosmetics of that solution, it should work every bit as well as the original design.

Welcome, Nick! It looks like a reasonably solid car. That would be a decent price here on the East Coast. I don't really know much about West Coast pricing. And of course I can't really assess the rust from the photos. I'm assuming it's doesn't have much. I think the fact that it's a daily driver in California (an emissions state) probably speaks well for it. As Chas said, the EFI Z's are primitive, but you can get them running well enough. (Again, in California, it probably already IS running well enough pass emissions.) The problem with some of these systems is that they drift leaner with age, although this seems to be a problem more with '78 and possibly '77 models than anything. But if your ECU drifts, there's a simple electrical modification to tune it. You can also tune the airflow meter mechanically. And somewhere on the horizon, one of our list members is developing a modern, digital, drop-in replacement for our aging ECUs. I presume you already know what you want, but I'll just point out that the 240, 260, and 280 each offer something a little bit different. There are threads you can search on this very subject (e.g. "240z vs. 280z"). There are good reasons to choose either, so pick what you like. Oh, and I think you will find this is a very good list. It's a bit slower than some, but it's very civilized here. And we have a lot of very good people who know these cars quite well. This list is more into stock configurations. A list like hybridz is where you'd go if you want to go nuts with mods.

Welcome! Nice 240! You asked, "Could the carbon be from the run-on?" I think it would be the other way around. Usually run-on is caused by carbon accumulation in your cylinders, which raises the compression. That's why higher octane gas remedies the problem. But it's only a remedy, not a cure. FAIW, octane ratings nowadays are not the same as octane ratings back when the car was manufactured. I don't know a lot about them -- how they differ -- but I do know that an 87 octane gas today is equivalent to a higher octane rating from back then. I don't know what 1970's 91 octane that Datsun recommended would compare to today. Perhaps 89? As long as you don't get knocking you can use any grade of gas. I use 87 in my '78 280Z. It works fine. My engine is happy with it, so there is no reason to use higher octane. Anyway, your engine's intolerance to regular gas is probably more of a symptom than anything else. Your engine seems to be running rich, hence the carbon accumulation (check your plugs to confirm -- probably black) and the boost in RPM when you engage your leaky brake booster (which leans the mixture). I suspect if you correct the lean condition, your engine will slowly burn off the carbon by itself. Until that happens, run the higher octane gas. Eventually, after your engine cleans up, you should be able to run 89 or even 87, unless your head was shaved to raise compression or something. If you do confirm a rich condition, correcting it will involve practicing voodoo on your SU carbs. You can find experienced voodoo practitioners on the carb board on this forum.

I'm sorry to hear about your dent! If it's any consolation, I have one just like it, so I feel your pain. When I did this test, I didn't measure leakdown with a gauge. Heck, I'm not sure I can even blow hard enough to register much on a gauge, even having played oboe in high school. You should be able to feel what's going on just with YOU. There's a certain rate at which you can blow air into your engine, depending on leakage. You can get a pretty good feel for that. And there's a certain rate at which pressure will leak down to the point that you can blow more air in. You can feel/estimate that too. You can compare this leakage rate with a known leakage rate through a small vacuum fitting, e.g. the HVAC control line that attaches right next to the brake booster line. I found that my vacuum leaks, in combination, were FAR less substantial than leakage through that open fitting, and I was satisfied with that. If your leak-down occurs through your valves, it would have to be either from open intake to open exhaust or through the intake and out the rings. Either would be abnormal. You could try turning your engine a few degrees to see if that seals things up. I have to mention here that I've never tried or heard about a "yogurt cup test" on a fresh engine. Perhaps it needs to be broken in before it will be tight. But honestly, if you assembled everything well, the engine should be pretty tight. You are not likely to hear any hissing, unless perhaps you apply some air pressure from a compressor (I'd suggest low pressure, maybe 10 psi). You might also try recruiting a smoker to help with the test. You can blow smoke into the engine and look for smoke billowing out somewhere it shouldn't. Backing a bit, and this is important, your plugs don't all read the same. Until the read the same, you might get a lot of mixed information from your engine. Furthermore, if your cylinders are doing different things, there are no settings that will optimize your engine's performance. That's surely why your max vacuum is 14 in Hg, and not at least 18 or 19. Thinking off the top of my head, and not necessarily in the order I'd test, I'm wondering... Do your injectors have the same flow rate? Being NOS, they might have come from different manufacturing lots with different flow characteristics. Usually parts from the same lot will be pretty much the same, so this isn't as likely an issue with newly manufactured parts. It seems unlikely this would result in wide variance from rich to lean. To test, try swapping your #2 and #3 injector plugs and see if the #2 and #3 plug readings reverse. I just checked the schematic for '78, remembering that the injectors are batch fired in two banks of 2 and 4. I don't know why the banks aren't split 3 and 3, but they're not. However, in the '78, the banks are 1/2/3/4 and 5/6. So that doesn't account for the differences between 1/2 and 3/4/5/6. Have you replaced your ignition components? You might have some weak ignition issues resulting in incomplete combustion in 3/4/5/6. You might re-check your valve lash. Maybe adjustment differences between 1/2 and 3/4/5/6 could result in performance differences that would result in incomplete combustion in 3/4/5/6. Is your compression even across all cylinders? This would tell you a lot, including possibly some clues about the high (?) yogurt cup leak rate. Once you've got your cylinders doing the same thing, then worry about tuning the rest of the engine. For starters, I've never set timing the way you've done it. By the book, you would disconnect and plug the vacuum line to the vacuum advance. Then you'd time the engine to 10 deg BTDC. I think most of us find our engines like a few deg more advance. Mine is set to 13 deg BTDC. BTW, check the breaker plate in your distributor to ensure that it rotates freely without binding. That's a common problem with our OEM distributors. I would recommend first adjusting your AFM to the correct spring tension per the Atlantic Z article. This time you'll use an aluminum beer can, instead of a plastic yogurt cup. This will ensure that your AFM pegs out at the correct air flow rate. Beyond that, fuel delivery keeps increasing per RPM. Anyway, I try to stick with the design, and that's what I've decided for my own car. If you richen the mix by loosening the clock spring, then the AFM might peg out prematurely, such that there's no enrichment for higher RPMs, hence leaning out. After you've adjusted your clock spring to spec, then see whether your engine is running rich or lean. My guess is lean, due to what I'm going to call "typical '78 ECU drift," and you would fix that by adding a potentiometer in the CTS circuit. That will get you by until Lenny finally releases his much awaited Hellfire ECU.

HA! That's a new one for me! Learn something new every day...

I'm glad you're finding/correcting problems. I have yet to see an old car besides one of my own that doesn't have multiple problems -- usually small stuff, like a cracked vacuum hose here and a bad electrical connection there. To be honest, even my own old cars have one or two problems at any given time. Life gets in the way, I suppose. My Z has a bad AAR, but I've just learned to live with it -- tired of fussing with it. A fuel pressure regulator is a very simple and robust part. It's very unlikely to be inaccurate, because that would require the spring go kapoot. It can fail if the diaphragm gets ripped, but that's a rather rare occurrence as far as I can tell. I've not heard of any verified FPR failures, although I know lots of people change them out.

If your fuel pressure slowly fades away while idling, without rocking around, without sloshing around any debris in your fuel tank, I would still guess it's because of your fuel pump. I only say that because that's what my pump did when it failed. It's a vicious cycle: Fuel flow is somewhat insufficient to start with, and because fuel flow cools the pump, that means cooling is insufficient. So the pump slowly starts to heat. The warmer it gets, the more inefficient it gets and the less fuel it pumps, which means even less cooling, etc. Or it could be that the pump craps out when it warms up, irrespective of how much fuel flow is cooling it. Just remember, though, that by the time you get to 20 psi, there's almost no fuel flow at all, save for whatever passes through the injectors at idle. That is, there's no return fuel flow. So at that point, your pump could have a serious issue with staying cool. Irrespective, that's exactly what my OEM pump did when it failed. I replaced it with another OEM pump, and the problem was gone. The other thing I would look at is the electrical connections. In particular, the big wiring harness connector just inside the passenger firewall is IMO insufficient for the sort of current flow it gets through the fuel pump circuit, so it gets hot, arcs, chars, and melts the plastic. This happened to me a couple of times on my old pump (which might have been drawing excessive current at the time). I eventually snipped out the fuel pump wire (green and blue) and connected it with a bullet connector, which solved that problem.