FastWoman

You know, after I did the exhaust, the car was mostly inoperable (other issues). I haven't really gotten it out on the road much until now, and I realized I hadn't really done a proper follow-up on the exhaust. With the lean-running issues worked out, the exhaust has a sound sort of like a Porsche on steroids. It's a really deep note, and you can hear it from a pretty good distance. Come off of idle just a bit, and there's a tiny bit of rasp, but not much. Under load, the sound mellows out and doesn't get particularly noisy. Cruising, you can't hear a thing. I tried driving through a concrete tunnel at WOT with the windows down, and the exhaust noise was only slightly louder than the engine, road, and wind noise. It's definitely a good system, for my purposes. I'd recommend the configuration to anyone whose priority is civility and driveability.

Hmmmm.... Yes, I definitely have a few parts missing. I don't get it. The little branches are to blow A/C on your feet? That seems odd.

Yes, Steve, they're that bad! The only times I've ever had to tow my Z were due to intermittent problems -- once with a fusible link in my old '75, and once with the fuel pump wiring in my '78. I much prefer a problem with the common decency to stay broken until I fix it! I'll mention that the approach I suggest is a diagnostic approach. The other approach you could take is to pull apart all of your connections and clean them up. Then hope that the problem doesn't re-surface. Honestly, that may be the better approach for any old car. That said, if you don't find the problem in this process, be sure to carry that multimeter and wiring diagram. Heck, I pick up cheap multimeters here and there and have them stashed in cars and boats anyway.

Andrew, I think my car is missing that part. I seem to have slinky hoses from the air handler to both vents (driver and passenger). The only clue I could offer (maybe) is that the slinky hose on the driver side is in two parts. The end connecting to the vent appears to be original duct. The length from the end of that to my air handler seems to be modern material, and perhaps that's where you duct piece would go?

Hi Jenny, It sounds like your car is running lean! I think you've got vacuum leak issues going on. Frankly tape is not an acceptable material for anything other than wrapping wiring, and some people even take issue with that use. It's a fairly simple/cheap matter to round up some new hoses/tubing and to replace all of the rotted vacuum tubing mess you already have. It's avaialble at any auto parts store. The big hose that goes from the valve cover to the throttle body is important, and it's under vacuum. It's part of the PCV system and helps to keep your engine clean. If you have a big split in the thing, you're going to have a huge vacuum leak. That would certainly be sufficient to make your engine run very badly. There can also be other lean-running issues. Cozye and I have beaten our heads against our respective walls about our '78s, and we're both in a much better place now. However, both of us found that our engines were out of whack even with the sensors all within spec, with new injectors, etc. I concluded it was a semiconductor issue in our engine control units. These units have earlier linear circuitry, as compared to the digital circuitry of a modern ECU. They are prone to drift and degradation. Anyway, you can read about some of our debugging work in the "purs like a kitten" thread. Hey, girl power!

"forgot to mention that when I pulled into my driveway which is a bump everything started working again on impact..." Oh no! Those are the worst sorts of problems -- the intermittent ones! Chances are, if you hit enough bumps and drive the car long enough, the problem will get better for a while, and then when you least expect it, it will leave you stranded a few hundred miles from home. If I were you, I'd keep a multimeter and an electrical diagram (or Nissan Factory Service Manual -- available used on Ebay or Amazon) inside your car. Do a bit of minor disassembly around areas you might do fault tracing (e.g. your steering column cover, fuse box cover). See if you can get the electrical circuits to fail. If/when they do, then go over the car and see where you do and don't have power. Be very gentle, as you don't want to randomly give something a wiggle and have your circuits wake up again. It's easier to find the problem when it's being a problem. Start with the fuse box, which should already have the cover off. Feel gently for any hot fuse ends. Heat generally means corroded, arcing connections. Clip the negative wire to a body part, and gently start probing all of the fuse *clips* on both sides. Don't pull any fuses out. The clips on each side of any given fuse should have the same voltage. Otherwise either the fuse is bad, or the connection is corroded. The fuse block is divided up into major circuits (e.g. battery, accessory, ignition, lights). If everything is turned on, every terminal in the fuse block should be live. If you have an entire section that's out, the culprit is probably something like a fusible link or a major power switch (e.g. the ignition switch). If EVERYTHING is dead, it's more likely the secondary wire off the positive post of the battery. As Steve suggested, you might be able to trace the problem by asking what all your dead circuits have in common that your live circuits do not.

I'll see what I can figure out for you. I don't know what I'll be able to see, especially on the passenger side (behind the glove box). But I'll take a look.

Good point, Bo. The vacuum lines actually pre-date all of my recent work. As I mentioned somewhere, I'd like to fabricate some mandrel-bent metal tubing pieces for the much of the vacuum lines. I'm not yet sure how to do that. I'm thinking stainless, with black silicone rubber connections. Anyway, I think that will be a small project for the spring/summer. I have a boat to get put back together for the winter and a poor, black Saturn (next to my 280Z) whose side was shattered by a deer. (I almost drove the Z on that trip! Thank goodness for engine trouble!)

Andrew, I think I have slinky hoses on mine. I had assumed that was the OEM configuration. Maybe not? Or is it that slinky hoses come out of the air handler and connect to one of the things like you're holding? I'll take a look when it's daylight and when it stops raining.

Olzed, I just went for another spin today. My engine runs beautifully. Now that I've learned the EFI and have figured out how to make adjustments to the mixture, I don't think I'll have any more headaches. I've certainly beat my head against the wall about carburetor problems before. In fact I have a Holley carb I have to rebuild and put back on our boat. It's a royal pain in the... er... boat!

Oh, man, we were just out that way -- well, south of there, anyway. We brought back a nice virus from Virginia Tech. The fall colors are in their peak (well, just passing their peak, I suppose) here in the Tidewater area. We took a ride along the Colonial Parkway today. It was cloudy and drizzly, but the colors were spectacular. I understand we have some 20 mph weather coming in, so I guess that's the end of the colors for this year. For those of you who don't know the Colonial Parkway, it's one of the obligatory drives in this country. The Colonial Parkway is probably as pretty in the fall as the Pacific Coast Highway is the rest of the year. It's a slow drive (45), but always just gorgeous. Another great fall drive is the Hocking Hills area of Ohio. Then there's Spring in the Texas Hill Country -- around Brenham! Ah, the wildflowers! My car is now doing wonderfully, and it was a delight to drive. (I wish we could have taken it to VA Tech, but I still had some fuel issues then.) I don't think there was ever a better road car than the 240/260/280Z.

Oh, man, my car is a lot better looking than I am, with middle age bloat and everything. I'll try to get a shot, though. You too, Leonard!

No problem, Cozye! It was really nice being able to think out this problem with you -- somewhat of a "buddy" system, I suppose. I think your decision to put the AFM back to OEM specs is probably a good one. It's a semi-mysterious device whose air flow and response patterns probably took a big investment of R&D. It's designed to peg out at a certain air flow rate, and the ECU, which is (literally) a black box for which we have very little information, is engineered to respond to readings from the AFM on the basis of those response properties. The better fix is probably the one that applies throughout the operating range of the engine -- i.e. via the coolant temp circuit. I think time and use will help both of our engines. I know that my little BMW Z3 was a bit fussy until I drove it for several months. Then it ran great. Non-use really takes a toll on a car, particularly an older one.

Thanks, guys! I think "clean" comes as a major compliment especially from the 240Z camp. The stock '78 engine is a difficult thing to make look clean. My general approach was to organize it in parallel and perpendicular lines. When I have time, I think I'll try to clean up the vacuum lines a bit, perhaps fabricating metal tubes. I really liked the Duplicolor paint. I decided not to fair out the intake manifold for now, leaving that for later if/when I get to the point of a rebuild. I just decided to see how the paint looked on the rough aluminum. The second photo shows the effect pretty well. It's sort of a cool, dimply effect. Even the ridges from the seam lines in the casting look fine. I wouldn't hesitate to paint any rough metal with this stuff! BTW, I used Ztrain's method of putting the thermostat housing back together -- with stainless studs and nuts securing the top. When I removed the thing, I had a siezed bolt I had to drill out. I couldn't believe just how cemented that thing was. That will of course never be a problem again. The unit is still attached to the head with bolts. The original long bolt that went to the timing chain area was fine, being oiled from the backside. The other was frozen and had rung off. I replaced it with stainless and lots of nickel antisieze.

At least one of you asked for them, so here they are: The engine paint is Duplicolor's MetalCast blue, with base coat. The black is.. er... black. Everything silver is stainless. Most of the bolts on the intake are allen-head. In hind-sight, I would have ordered in the right size $2 allen-head screws for the injectors, as they would have been much easier to install. You'll notice I've replaced the valve-cover-to-throttle-body hose with a pipe. I think it looks better that way. In the middle of the following pic, you can see my MSD disconnect for the injector harness. The harness is integral with the fuel rail, which is wrapped with rubber hose and then silicone rubber tape for insulation. I did the valve cover by spraying the lettered area black, filing off the tops of the letters, masking, spraying the rest blue, and then clear coating the whole thing. My infamous AFM, the MSD Blaster II coil, and my HEI ignition retrofit (lower part of frame, with heat sink). The air cleaner came out nicely, I think. Cozye, here's the whole car. This is the last pic of my perfect hood before I slammed the hood on a tool. Now there's a little ding about where the white speck of debris is in this pic. I also had a request for a pic of the rubber stripping on the leading edge of my quarter window. It's deteriorated, but this is what it looks like:

Ah, but there's a certain magic about a Grammaphone, in comparison to an MP3 player. Same is true of the clunky vane-type L-Jetronic fuel injection. I don't know whether that magic is worth the cost of some loss in performance and added fuel costs, but there's still something rather cool about it. I presume if you go to the MS system you'll post all about it on this list. I think I'll let you go first! I did sort of close things up today. I did another cold start at last night's settings, and the start-up was fine. Idle was a bit low-ish (1200), but the mix was comfortably rich and stayed rich until the engine was warm. I've decided my air regulator does work. It's just that I don't get quite as much RPM boost from it now. Before, my engine was fuel-starved, so the enrichment made the RPM pick up a lot. Now the engine is no longer fuel starved, so the added fuel perhaps drops the efficiency a bit. I set my idle to 900 RPM. It just sounded so much smoother/quieter than the 800. I advanced the timing to 14 deg BTDC. My vacuum, in the end, was about 17.5 - 18. I don't know why I couldn't get as high a vacuum as before, especially with the slight timing advance. At a faster run the idle was more like 21, whatever that means. I also found my compression gauge and checked compression. The dry/warm readings were 165, 165, 168, 173, 165, 168. Perhaps a bit of engine wear there, but at least it's pretty even. I might still have some engine sludge issues. My engine was the sludge monster when I bought the car. I'm now starting to see about 60% clean metal. I changed the oil again today. I'm trying Chevron Delo now (for diesel engines -- very high detergent). We'll see how it goes. Anyway, with a bit of regular use and continued elimination of sludge and varnish, I might pick up a an inch or two of Hg.

Oh, and you had asked me whether I had considered MegaSquirt. I did think about it, but I didn't put too much time into studying it. I was discouraged by the fact it's incompatible (I think) with vane-type, closed-loop systems. I didn't want to get into a major redesign of the system. I think more and more of these EFI systems are going to be going south, and maybe there will be enough people wanting to stick with EFI (rather than converting to carb) that there will eventually be a turn-key retrofit for our systems (whether vane-type or something more modern). When such a system surfaces, I might well make the switch.

Cozye and I have been grinding out teeth at nights, trying to get our '78 EFI systems to work right. My most recent efforts are documented under the "purs like a kitten" thread. In short, I went through my entire fuel/intake system, doing some work that definitely needed doing, checking out all the components, refreshing, refurbing, etc., and I still ended up with a system that was running much too lean. I even acquired a spare ECU and tried that. Same thing. Also the same story with Cozye. He's verified EVERYTHING -- at least twice. He's been more thorough than I have. His EFI is running lean. All my sensors are spec, fuel pressure is right, injectors are new, connectors are new, everything checks, and I have no vacuum leaks, so the most likely problem, in my view, is the ECU (or more accurately, BOTH of my ECUs). Transistor circuits from the 1960's and 1970's don't have the same sorts of negative feedback controls as their linear IC successors, so they aren't as stable. Of course neither is as stable as the digital circuits that followed. Semiconductor performance fades and drifts over time, particularly in the old stuff, and the circuits may not be performing within their original design parameters. Anyway, that's what I think has happened to our ECUs: They've faded and drifted over time. While they might still be responsive to changes in sensor readings, they might be out of whack overall. Add to this that our systems weren't designed for ethanol gas, which requires a richer mix. Modern lamda-type EFI systems are able to adjust the mix dynamically, based on exhaust O2, but not our systems. The solution that I used to get my system running pretty well was to put a variable resistor in series with the coolant temp sensor for adjusting the fuel/air mix. Note that this approach (adding resistance) richens the mix, so it's only useful if you're lean to start with. If you're starting out rich, the best approach might be to adjust the AFM to a higher spring tension, per the instructions on Atlantic Z. Although this is a bandaid approach, it seems to work pretty well (so far).

There's a whole gaggle of relays inside that big, black housing the fusible links are mounted to. You should hear a big "click" from there when you turn the ignition key. If you don't, then the system indeed doesn't have power. Fusible link assemblies are a common culprit, although you say you've addressed that issue. You might have a corroded assessory wire coming off the positive cable to your battery. Look for a crunchy bulge beneath the insulation, right by the cable connector.

Thanks yet again! I'll try that.

Thanks, Cozye Yes, I used the stock spring setting and ended up with a resistance of approx 2.6 k. I think I'm about where you are on the tuning. I'm pretty close and will be just driving it a while to get a feel for it. I'll periodically do plug readings, calculate gas mileage, etc. BCDD: Yes, I still have it. I'm pretty sure it's operational, but I suppose that needs a re-check. G'nite!

I promised pics and details, so here they are. I apologize for the washed out photos. I didn't take them to be pretty, but rather to be clear. There's a whole lot of black in these photos! I decided it would be better to put the inline potentiometer at the end of a pigtail, rather than inside the ECU. The first reason is that I can change out the ECU and still have the same mod. The second reason is that I don't have to go into the kick panel to change the mixture. I tapped into the EFI harness inside the main connector shell. There's a screw on the end of it, and the shell slides apart I clipped the small black wire in the #13 position (labeled on the inside of the connector) and connected the two pigtail leads to the ends: Here's the pigtail coming out of the EFI harness, which has been wrapped back up. The connector does not have the potentiometer attached: Here is the potentiometer assembly plugged into the end of the pigtail. I simply heat-shrinked the 20-turn trim pot to the side of the connector: The connector has a slot where it can be mounted on a prong. I bolted this prong underneath my dash, just above the hood release and vent control: ... and this is the connector mounted on the prong: Not shown here are the trim panels. The panel that goes across the bottom of the dash leaves a hole where the air/fuel mix screw remains exposed. Also not shown is the approx 5 ft extension cord I made for this connection. It allows me to make adjustments from the hood compartment area or the driver's or passenger's seat.

OK, well, I've modded my car. Results are pretty good. Construction details will be in the next posting. I think the enrichment isn't quite all that it should be when the engine is cold, but it's not far off the mark. Idle is a bit unstable; however, there's now something wrong with my air regulator. It seems to be stuck in the closed (warm) position, so my idle speed isn't elevated on startup. I'm sure when I get that fixed, my cold idle will be much more acceptable. Anyway, I've had my car out on the road now. It feels about like it did when I loosened the AFM spring. The response seems pretty well balanced. I might have a bit of missing at WOT. Also after I give the engine a good WOT rev to maybe 4000 RPM, the drop in RPM pauses/bumps at about 2500 on the way down, and when I get that little bump, there's an exhaust pop. Do you (or does anyone else) know what happens at this 2500 RPM mark and what it means and/or how to get rid of it? I know the pop means I've got raw fuel in the exhaust, but beyond that obvious point, I'm not sure why it's happening there. I'm thinking that might be where the fuel cut ends on throttle-down. Other than that, the engine seems to be running about right. The fresh plug I put in #1 reads OK -- a bit of brown, and perhaps a touch of chalky deposit on the electrode. I might be a tad lean. Tomorrow I'm going to pull all of my plugs, most of which are quite black and sooty from prior issues. I'm thinking they might be a bit fouled and could use a good cleaning. I'll also see if I can tweak my timing a bit. (I still have to fix my timing light.) All in all, this seems to be a pretty workable solution. I like this approach better than playing with the AFM spring.

BTW, I've also re-thought where to situate the series potentiometer. I think I'll put a little Molex pigtail connector on the ECU harness and make a little 20-turn potentiometer/plug doodad (incased in epoxy?) to plug into it. Then I'll make an extension cord that will allow me to make adjustments from a seated position (passenger or driver) as the car is moving. Once the correct calibrations have been determined, I'll remove the extension cord, save it in my "special tools" box, and have it available for future "while-driving" tune-ups.

I've been thinking about how to tune this system. I suppose if I were racing, I'd want peak efficiency at WOT when running the engine at the peak of the power band. However, I'm not a racer. I'm just a semi-puttery, middle-aged woman who wants a cool car and doesn't want to destroy her engine by running it at the wrong mix. I'm first going to determine which series resistance gives me the fastest cruising speed at a fixed accelerator pedal depression. Then I'm going to see how that same setting translates to WOT conditions. I suspect I'll run right much richer at WOT. I might get a tiny bit more power running a tiny bit leaner, but my preference would be to optimize for cruising and to be "safe" at WOT. I suspect that's how the Nissan/Bosch folks designed the system in the first place. Finally, I'll see how the engine idles at this setting, and I'll make any needed adjustments to the little AFM screw. BTW, you should remove your screw and examine it. It has a rubber O-ring near its head, which I think mostly serves to keep the screw from wandering. Mine had crumbled practically to dust. (I honestly thought it was dirt.) I replaced it with a tiny sliver of silicone rubber hose that I carefully cut with a razor knife. The screw now has a bit of "hold" to it, and I'm confident it will stay in place. At this moment I have it set rather arbitrarily at 5 turns CCW from fully closed.