FastWoman

I've restrung mechanisms like that (in several antique radios) with some fishing line that came to me by way of my grandfather. It's a finely braided line, probably nylon, that I imagine was used for fly fishing.

Thanks, Nissanman! That diagram helps a lot. Ztrain, the thought had occurred to me.

Nissanman, it's definitely not the anchor points for the spring that causes the pop. I guess the clevis pin makes sense. Does the push rod just pull out of the clutch master (i.e. with nothing else attached)? FirstFruits, I'll definitely report back what the problem is that I find, but I don't know when I'll have time to get to it. Lots of irons on the fire.

Really! OK, that changes everything. I suspect a MegaSquirt system is in my future -- or at least a MicroSquirt mounted inside the OEM ECU box. That said, my car is running pretty well right now, so I think that's a project I'll save for (much) later. Of course I'll keep a lazy eye on what Cozye is doing too. Maybe by the time I'm ready to convert, some kind soul will sell a turn-key, plug-n-play ECU retrofit. That would be nice.

Cozye, yes, you're that special "someone!" Rob, I agree that the L-Jetronic system is pretty dumb, but I have a strange affinity for primitive technologies. I want a system that utilizes the stock, vane-type AFM, just because it's old and different. I have no special affinity for the analog electronics in the ECU. I suppose my ideal system would be a MegaSquirt digital ECU that would utilize the signal from the vane AFM and perhaps also fine-tune via an O2 sensor. Another possibility, since it's just a dumb analog ECU, would be to build a fully adjustable analog ECU with modern linear circuitry design. This would require that I reverse-engineer the original ECU, of course. FAIW, I made a special extension cord for my AFR adjustment potentiometer, so that I could have my wonderful assistant drive my car while I made AFR adjustments from the passenger seat -- e.g. seeking out the fastest cruising speed at constant throttle. I found that the ideal settings under load were pretty similar to the ideal settings in the driveway. (I was rather surprised by that.) BTW, I can buy a "rebuilt" ECU through AutoZone and am certain I can find one elsewhere too. However, all the electronics are proprietary, mysterious, and obsolete. I suspect the "rebuilding" process amounts to little more than cleaning the thing up, making it look pretty, fixing anything obvious (e.g. a bad solder joint), putting it in a nice box, selling it, and hoping it doesn't get returned. Short of having Hitachi's documentation and a stock of NOS replacement parts, I doubt there's anything else that can be done.

Mine was installed by the local Z specialist, who has done a number of these MSA exhausts. He installed it without a mid-point hanger and seems to work fine that way (so far). I had asked him about a midpoint hanger, and he said it wasn't necessary. If you think about it, the absence of a midpoint hanger gives the system more freedom to rock with the engine. Anyway that's my system. YMMV

Oh yes... Zed Head and Cozye are correct about the fuel pressure! I had misread and thought your reading was without the engine running (in which case it would be roughly normal). The fact remains, though, that richening the mix raises the idle. Fixing the fuel pressure problem will lean the mixture a little. It certainly needs to be done, though. I think it's important, BTW, to go ahead and tweak the AFM with your finger to attempt to find the best/highest idle, preferably with a vacuum gauge attached. If it feels/sounds pretty good, and if you can pull a pretty good vacuum (ideally 18 or 19), I think you can rule out ignition problems and gross mechanical problems (e.g. valves). Also I want to be clear: I don't think you should ordinarily adjust the AFM, either now or later. Quite the contrary, I think the best final solution is to fine-tune the coolant temp sensor circuit. But again, that's for later, not now. One final note: I'm remembering how horrible one of my thermostat housing bolts was. The bolt was deteriorated and rung off. I also removed the thermostat housing from the side of the head, and the shorter bolt (towards the rear) rung off too. Fortunately the latter bolt could easily be removed with vice grips, as the jam was mostly in the unthreaded hole running through the thermostat housing. (I had to pry the thermostat housing off of the broken bolt.) The first rung-off bolt was the worst I had encountered anywhere on the car. I ultimately had to drill it and chip out the remains of the bolt, and even that was pretty hard. Sooooo... If yours is like mine was, there's no shame in taking it to a mechanic who has the tools to replace the thermostat. Another note: After you get the thermostat housing apart, clean up the threads with a tap, and install a couple of threaded stainless steel studs (which you make by hack-sawing the heads off of a couple of SS bolts). Use nickel antisieze. Then secure the thermostat housing cover with a couple of stainless nuts, regular washers, and lock washers. You'll never have a difficult removal again. (That was Ztrain's excellent suggestion.)

Yeah, probably. I'm just waiting for someone else to do it first!

Jenny, your AFM test establishes that your engine is running too lean. (I think your shot of carb cleaner into the intake might have been too much.) When you open up the AFM flap, it signals the computer to deliver more fuel, which causes your engine to run faster. You can go ahead and move the flap further than 2-3 mm with your finger. Go ahead and move it as far as you need to, in order to achieve the fastest idle. When you keep moving it farther and farther open, you'll go past that peak point, and then the engine will start bogging (as the mixture gets too rich). That will give you a preview of how your engine will run with the proper adjustments and repairs. (1) First thing is to replace the thermostat. Sometimes you can loosen a bolt by hitting it with a blow torch and then letting it cool back down. Be careful, though. You can also try tapping on it lightly with a hammer. Obviously be very careful not to ring off the frozen bolt. If that happens, though, your next step would be to use a blow torch and a pair of vice grips. (2) Next is to establish that you don't have any remaining vacuum leaks. The very best way to do that, IMO, is to do a whole-intake test such as I've described. Remove the AFM, plug the rubber boot with a yogurt cup, and "inflate" the intake manifold by mouth through an intake fitting. If you find you have a leak that way, your next steps can be to track down where it is. (3) After you've gotten your engine solid, then make sure all your sensors are within spec, per the EFI bible. (4) Then after all that is done, you can richen your fuel/air mix as much as needed by inserting the potentiometer in series with the temp sender. This will compensate for drift in the calibration of the ECU that has probably occurred over the decades. That's your four-step plan, to be taken in that order. Have courage with #1! Peace, Sarah

Thanks, guys! I was afraid it might be something like that. I hate working in that area! I might feel a bit differently if I were an 8 year old kid, but I can barely get my arms up in there! Groan....

It's great when my greater issues boil down to little annoyances So I'm wondering what's up with my clutch pedal. It's well greased and seems to move freely without binding. When I depress the pedal, it moves smoothly. If anything, I can hear the very faint sound of the return spring stretching out -- I suppose slipping in its mounting holes. Then when I let clutch pedal back out about half way, there's moderately loud click/pop that I can feel with my foot. I've spent some time with my head under the dash, trying to figure out the source of the pop, but I don't see anything. Is this a common problem? If so, what's its cause?

Mike, if you want your ammeter to read correctly (assuming it has numbers on its scale), you'll need to keep the same shunt. The gauge of wiring that runs to it and/or the type of alternator on the other end is irrelevant, as far as the operation of the gauge is concerned. I don't know many/most details of the wiring of your 240, but I would think you could consider this alternative approach that might be a bit easier to retrofit: (1) Identify the wires that run between the ammeter and the engine compartment. (2) Move the shunt from the back of the ammeter to the engine compartment, connecting it between the outgoing and returning wire. (3) Run your heavy wiring everywhere else (from the alternator to the shunt, from the other side fo the shunt to the fusible link, from the other side of the fusible link to the battery) The heavy OEM wires running from the shunt to the ammeter will then carry very low current and will be overkill, but at least you won't have to strip them out of the wiring harness running under/behind the dash. If you want the full scale of the ammeter to reflect more amps (e.g. 60A, rather than 40A), find a lower resistance shunt for it. You can make your own shunt out of a strip of iron/steel. To change from a 40A to 60A full scale reading, you'll need a resistance that's 2/3 the value of what you already have. Alternatively, you could keep the shunt you have, and insert another shunt in parallel (bolted to the same terminals) of twice the resistance value. You'll need a really sensitive and accurate meter to measure these low resistances. Either that, or you'll need to measure the resistance of a very long piece of the material you're going to use, and then you can calculate the ohms per cm to determine the length of shunt you'll need. Regarding the turn signals and brakes: Why not just go to electronic flashers and LED lights? That's what I'm going to do. The only problem is that my local auto parts store just sold out its entire stock of LED replacement "bulbs" because nobody would buy them, and I missed the chance to scoop them up out of the 75% off clearance bin. Grrrrr...

Cozye, I'm not proposing this as a means of altering the functioning of the ECU, but rather a way to offload current from the ECU's power circuitry. In other words, it's a way to make the ECU last longer.

Hi all, In the same spirit that we replace thermal flashers with electronic flashers, do relay modifications on our headlight circuits, and replace incandescent bulbs with LEDs, I have an idea that would help to preserve the integrity of the ECU. Furthermore, it would substitute standard, off-the-shelf parts with known parameters for the power circuitry inside our black boxes. In short, we should be able to remove the drop resistors in series with the injectors, substitute a power transistor assembly to regulate current, and then wire the injectors into two banks of three series-wired injectors. One end of each series would be grounded, and the other end would be fed by a PNP power transistor -- emitter to +12, collector to the string of 3 injectors, and base to a resistor and then to the ECU output (which drags voltage to ground to fire the injectors). The injectors are 2.3-3 ohms, and the drop resistors are 6 ohms, so it is not unreasonable to have 3 injectors in series. In other words, the needed current could be supported. In fact one could probably ditch the drop resistors, wiring 3 injectors in series directly to the ECU output, but there was probably some reason that wasn't done. Depending on the value of the resistor on the base and the current gain (hFE) of the transistor, the current through the injector series would be current-limited. That would be appropriate, as it is the current that determines the magnetic flux. Benefits of this design: * eliminates the big drop-resistor assembly * offloads current demands from the ECU * creates a new circuit with known and replaceable components * eliminates 8 wires in the injector harness * less power hungry = less draw on the electrical system Modifications to design: * If needed, a common injector control output could be used to power both banks (e.g. if one were to have failed) * If needed, the design could be used to create three banks of two injectors or to wire each injector with its own power transistor. Other factors: * It's necessary to substitute a power transistor assembly with heat sinks for the drop resistor array. I presume the best place to mount the assembly would be where the drop resistors are removed. Heat dissipation should be minimal with the 2-bank configuration -- probably less than 2-3W total. It shouldn't require much heat sink. * An interesting mod would be to attach the power transistors to a billet aluminum fuel rail, so that they would be liquid cooled. The supply to the rail would then be +12, GND, and the gate signal (i.e. only 3 wires). I obviously haven't done this yet, but it will probably be on my list of things to do the next time I'm into my fuel injection system -- probably long into the future. Until then, I'll be sticking a postit note in my FSM with this circuit diagrammed. Any thoughts, anyone, without telling me this is unnecessary nonsense?

Sure thing, Mike. Don't worry, though. It's a pretty easy job. Just unwrap the wiring harness, pull out the scary, crimped, white and white/red wires, and make the requisite improvements. (I don't know how the 240s are wired.) For my alternator wire I used thin-insulated, teflon ensheathed 8 gauge like would be used in 220V household wiring -- sold by the foot at Lowes. I made my own alternator post connector out of a piece of copper tubing that I crimped around the wire (pinching one side of the tube) and soldered. The lug was made by flattening the other side of the copper tube in a vice and drilling a hole. I made other heavy connections by crimping inside small lengths of copper tubing, soldering, and wrapping with tape. I think I bought the Stinger maxifuse block off of Ebay. The bare end of the alternator wire clamps directly into the fuse block, and the block is fed by a 6 ga cable from the starter post. When you're done, just break out a roll of electrical tape, and wrap it all back up. It's probably a 1-2 hr job from start to finish, once you've assembled the parts, but if you're like me, you'll also do the headlight relays once you're into it.

All of what Cozye said! Don't be afraid to tweak the AFM mechanism a bit with your finger. You won't break it or blow anything up. Also don't worry that you're altering air delivery to the engine. You're not (or not very much). As Cozye said, you've established that your engine isn't running lean (provided your movement was very small). So now try it in the other direction. By closing down the AFM mechanism just a bit, you'll be leaning your mixture. Does that make the engine run better? Also does it run better if you open up a vacuum leak somewhere (e.g. by pulling a vacuum hose)? All of this would mean you're running rich. Possible causes could be running too cool (i.e. bad thermostat), a bad temp sensor, too high fuel pressure, worn injectors, and/or a stuck (open) cold start valve and/or inoperative thermotime switch. If your engine is running super-rich, the latter two possibilities would seem all the more likely. You'll be able to tell a lot by the plugs. However, in my experience, a very badly running engine will give you somewhat sooty plugs even if the cause is a lean mixture. It's only when all cylinders are hitting reliably that plugs can get that chalky, white, "lean" appearance. Other issues: Rust on headers -- Don't worry about any "cancerous" effects spreading to other engine parts. Also don't worry too much about the life of the headers. Most exhaust parts rust from the inside out, where condensation pools inside. The headers are not prone to moisture accumulation. The only issue will be appearance. Rusty oil pan: Well, there's rust everywhere on these cars. I've never heard of an oil pan rusting through, though. It's never a bad idea to paint something, but first you have to get it quite clean. That's going to be hard to do with an oil pan attached to the bottom of the engine, mounted in the car. If you ever end up pulling the engine, definitely paint the pan then (as well as other engine parts). Otherwise I wouldn't worry about it if I were you. (For instance, I didn't try painting my rusty engine block when I had the manifolds off of my engine. I thought about it, but I didn't feel I could do a very good job of it without subjecting it to a chemical soup that might be hazardous to other parts of the engine bay. I just scrubbed it a bit, sprayed a bit of fogging oil, and left it.) I do all of my painting/de-rusting opportunistically. Whenever a part comes off, it doesn't go back on without being de-rusted and painted (and that makes it slow going). FYI, you can do a lot to stop rust by wiping an area down with Ospho (available at your local hardware/paint store), letting it dry, and then following it up with fogging oil. (Obviously don't spray your headers with fogging oil!) You can also do some local rust proofing with a WWII era product called cosmoline (http://www.cosmolinedirect.com/). That stuff is on my "to do" list.

Maybe you're running carbs on the car? I wouldn't think an EFI car would even run on 3.5 psi. If you've got EFI, then either you've got a bad fuel pump, bad fuel pressure regulator, or clogged up fuel system. That would make it run very lean and would cause your intake backfires.

"For people replacing links with maxi-fuses, are you still comfortable with the fuse ratings given what I have managed to dig up?" Everything is still working great! The fuse ratings I've used work fine. However, be warned that my alternator line is upgraded to 8 ga wire, so it can actually carry the amperage I've fused it for. I'll also mention that the Stinger fuse blocks are working fine, even as they get rained on through the hood vent. I put a strip of clear packing tape over the top one to shield the water, and that works fine. Without the tape, the gold-plated steel screw plugs would rust. Cozye, I decided to make the conversion because my fusible link assemblies were falling apart (both cover, base, and wire), and I could find no suitable replacements. I also feel, in hind-sight, that the maxifuses are much more solid, electrically. I admit I get a little smile on my face whenever I switch on my headlights and see that beautiful, bright, white light effortlessly coming out of the front of my car. It's the result of three upgrades -- alternator wire, maxifuses, and headlight relays. Mike, even my '78 280 w/ 60A stock-configuration had a severely overstressed charge circuit, with a couple of black, melty areas to show for it.

Summer, the "middle muffler" could be a resonator, which is essentially a shell of a muffler that is intended to create additional sound reflections in the exhaust. This is done to break up wave fronts, redivert them, recombine them, and cancel out much of their energy. It's also a way to break up strong resonances at certain RPMs -- to smooth out the noise suppression properties over the entire RPM range. You can replace a resonator with a muffler, which works a bit differently, but still achieves some of that effect. There are a number of small, cylindrical, glass-pack mufflers you can insert mid-pipe. I used a Magnaflow 4" dia stainless steel muffler as a midpipe unit on my exhaust. My exhaust is fairly tame (but with a very nice, deep note at idle).

mgood, sorry for the hijack, but were your mirrors made by Nissan, or were they an aftermarket option? I bought a pair of the exact same mirrors (except in flat black) off of Ebay to replace the junky Advance/AutoZone/Jegs mirrors that came on the car. Any idea where I can find the plastic mounting gasket?

Thanks, Bonzi, I'll pick some up! Idaho, I don't think it's a matter of engine failure, so much as unnecessary engine wear from particulates that either fail to be trapped or that are re-released. There was of course a time when engines didn't have oil filters at all, and they didn't fail catastrophically from it. However, they also didn't last as long as modern-day engines.

Not many people on this list will have the slightest clue about ZX wiring, including me. (I'd need a schematic diagram and/or some familiarity with that series.) However, these ignition switches and ignition locks do wear out. If you want to know what's happening with your power, put a volt meter on various circuits in your fuse block. You'll have an accessory circuit and an ignition circuit. Obviously the accessory circuit should be energized with the key in the ACC position, and the ignition circuit should be energized with the key in the IGN position. Neither circuit should be energized in the OFF position. If you don't find this to be the case, either your ignition switch is bad, or something is wired wrongly (or possibly shorted). You should be able to find a Nissan factory service manual for your car on Ebay or Amazon (used, of course). That would be enormously helpful for locating the problem.

Well, 13V under full load at idle is probably within normal limits for that alternator. They vary quite a lot from unit to unit. You can measure your voltage drops across various conductive paths while your system is idling under load. For instance, to test the voltage drop of your alternator wire, connect the (+) side of a volt meter to your alternator's positive post and the (-) side to the (+) post of your battery. That reading will tell you how much voltage drop you're getting. Also if you can determine or guess the amperage you're passing through that wire at the time, you can compute the wattage being dissipated in the wire as heat. It will be the current times your voltage drop reading. For example, if you're pulling 40A through that wire and experience a 1V drop, you're generating 40 W of heat from that wire -- same as a 40 W light bulb, except distributed along the length of the wire (or perhaps even focused at hot spots like corroded crimp connections). Remember that the heat that is generated is trapped inside the wiring harness and doesn't dissipate very easily. BTW, Dave is 100% correct that the voltage problems don't end there. Forty years of corrosion compromises the integrity of your entire electrical system even under the best of conditions. You could be losing voltage anywhere there's a non-soldered connection -- crimp connections, plug connectors, screw connections, fuse clips, etc. You can trace all of your voltage drops as I've described above, so you'll have some idea where the problem areas are that need to be cleaned up.

Zinc for the valve train? No. Is there an additive you like? I might do the Seafoam before the next oil change. The valves are pretty free, though. I run a bit of B12 in my fuel from time to time.

Ztrain, I used Rislone in Castrol Syntec for 1000 mi the last time around and am running Chevron Delo right now. Detergent seems to be doing the job -- slowly and gently. After I get the bulk of the crud knocked down to size, I might do a final clean-up round with a Gunk flush. The good news is that I'm seeing about 2/3 metal and 1/3 polymerized black crud right now. Making progress.