FastWoman

Andy, the VR in my '78 alternator (internally regulated) was slowly going bad several weeks ago. The regulation point kept climbing, until it reached 16.25 V one day. I ran my headlights on the way home to drag down the voltage a bit. I had a replacement alternator installed the next day. Anyway, my 16.25V didn't seem to blow anything out. Even the battery was fine. Maybe I was just luckly. Bulbs are probably going to go out long before fuses. Fuse values are appropriate to wire sizes, which are (usually) much more than adequate to feed the bulbs. FAIW, 14-14.5V is a good, normal charging voltage.

I got the grids today. They feel very much like my BFGoodrich T/As did. However, I've not driven them on dry pavement yet. The fit is much better -- no rubbing. The tires are noticeably smaller, but not objectionably so. Having the narrower tire (195) on the wider rim (7") looks perfectly fine. Glad to be back home. It's been a rough day, between the tire shop possibly tweaking my front end OUT of alignment, an elderly woman trying to attack me with her car as I was leaving the tire shop and she was leaving church, and an exploding tartar sauce bottle at lunch.

Lead-footed driving in my younger days in my '75 -- about 16 to 18 combined city/hwy More sensible driving in my '78 -- about 26 hwy and 18 city. Mileage will probably improve as I continue to work bugs out of the engine. I think there was a thread on this a few weeks ago. Lots of responses.

OK, here we go... I'm a whole lot closer with the new coil: Peak voltage=500V Burn time=1.6 ms I did multiple captures, and this is about as normal as the waveform gets. Some waveforms took negative swings of -200 to -300 V. Some have a much shorter burn time. There's all variety of randomness from pulse to pulse, including large variations in burn time and waveform. I spoke too soon about the false triggering of the tach disappearing. It still false trigger on hard acceleration, albeit not nearly so much. I also scoped the +12V rail to see if I have some problem with the alternator. Although it doesn't look like it in the above trace, the voltage is mostly quiet. I get the same low level quavering, but I see it at all scales in about the same magnitude on the screen (i.e. not of the same absolute voltage). It seems to be internal to the oscilloscope, relating mostly to the fact I've not been thorough in grounding the oscilloscope to the computer. What I did see was approx. 16V spikes over baseline (i.e. 30V peak, with respect to ground) from the ignition spikes, measured at my MaxiFuse block. I'll be replacing the condensor off the + post of the ignition coil. I checked at a local auto parts store, and they don't have the Nissan-style condensor (with two wires with bullet connectors). I'm guessing these noise suppression condensors are all approx the same, since values aren't specified? I have a new condensor off of my last alternator, which I can tip with a bullet connector and bolt to ground. I'll try that. Anyway, although the waveform looks much better, it's still very irratic. My next step, I think, will be to replace the ignition module. Then everything will be fresh and internally compatible: new/rebuilt OEM distributor and reluctor rotor and cap apparently very recent new NGK wires and plugs MSD Blaster 2 coil and finally... MSD 6A ignition module

Update: I got the MSD Blaster 2 coil and installed it. The engine started normally, but really missed badly when revving the engine until it warmed up for a couple of minutes (might just be coincidence, as it can be moody the first couple of minutes anyway). However, once I got past that point, the engine revved normally and ran smoothly. It continued running smoothly until the engine reached normal operating temperature, and then it started idling a bit more roughly, as with the old coil. Here's the interesting thing, though: The tachometer no longer has random spasms at idle and crazy swings on acceleration. Thus, I seem to have eliminated the high voltage ringing on the back end of the burn time. I don't know anything about the current waveform, as I haven't scoped it yet. I'll leave that for tomorrow afternoon, after I have the car fitted with new tires. I'm guessing I didn't actually solve anything, but simply tweaked enough of the operating parameters that I've diminished the ringing enough not to double-trigger the tach. I'm still betting my control module has gone funky. I'll know more tomorrow.

Hi Al, Interesting about the crossfiring. I googled it and found a small bit of info. Apparently it *is* an inductive phenomenon. The wire clips we have on our Zs are similar to other wire clips I've seen that are supposedly designed to space wires far enough to prevent crossfiring. There's a floating triple clip that I think is used for wires 4, 5, and 6 as they loop over the righthand side of the engine. Maybe that would have prevented your 5/6 crossfire problem? Supposedly you can see a corona in the dark around wires that might be crossfiring; however, that wouldn't seem consistent with an inductive mechanism. I'll have to give that a look nevertheless. I wonder if there's a capacitive component to crossfiring, in addition to the inductive. That would seem the more likely cause to me, as current flow is not actually that great. [edited out "bright idea" that didn't appear all that bright on reconsideration ]

Yeah, when they explained what I'd be paying to have them dismount tires, ship them back to tirerack, ship in replacements, pay to re-mount, I could see the $$$ adding up fast. That said, if you're just buying more of what you already had, tirerack is the way to go. When we had to buy new tires for the Expedition, nobody local could come anywhere near their price. We saved a lot of money. But if theyre's any unknown, you're right that it's good to go local.

Actually, looking at the tire ratings at tirerack.com, the Pole Positions rate very slightly higher than the Grids on comfort and noise, as well as all aspects of handling. However, calling a local tire store, I have found out that the Pole Positions have no tread wear warranty and would supposedly not grip as well on wet roads. Dunno... These tires really seem so similar, and both sound really great. I'll probably go with the Grids. BTW, if anyone is reading this thread with the same issues to address, I'm getting my tires at my local Tread Quarters shop. They're an installer recommended by tirerack.com. Because of a sale they're running, they're actually coming in slightly CHEAPER than tirerack.com if I buy my tires there. (I didn't think that was possible.) Moreover, and here's the main point, they have a 30 day ride and comfort guarantee. If I don't like the tires for any reason, they'll swap them out for another model. I asked about the specific situation of tires rubbing the fender, and they said they'd cover that too. Sounds like a winner. :classic: Thanks, Zedyone, for the photos and the useful information!

Hi Al and Kenny, Interesting about the cross-firing. I'd never heard of that. Did you see sparking between the wires? I can't imagine there would be a strong enough inductive effect, even though the wires are ferrite core and spiral wound. I had a set of translucent NGKs on my old '75, and they were the best wires I ever had on any engine. I think the wires are all opaque blue now (?), and I think the ferrite core is a relatively new thing. Anyway, I have no opinions yet on the newer wires. Everyone (else) seems to like them, though. Besides that, if I go with the MSD ignition module eventually, MSD says their equipment is incompatible with carbon core wires and requires the spiral wound type. In answer to your question, Kenny, I did test the individual wires with the timing light the same way Al did. I did get triggering irregularities on all wires that looked somewhat like bursts of "fluttering," so that makes a second device (besides my tach) that doesn't like what's going on with the ignition. Al, I sure do wish I still had one of my old Tektronix scopes. Those things were bulletproof. Unfortunately the ones I had were so old that the caps were all dried up and unreliable. I'm in awe of the capabilities of this cheapo Chinese oscilloscope I bought off of Ebay, which includes including some rather powerful real-time signal analysis tools that would give our old $100,000+ equipment bench (shared between labs) some pretty stiff competition. What the consumer oscilloscope lacks in volt scale accuracy, it more than makes up for in time scale accuracy, convenience, integration, versatility, and computation speed. Honestly, if I had the availability of this device back in the late 80's, I'd have finished my dissertation at least a year earlier. I just need to devise a better probe for using it on automotive applications. I really have to be careful about overvoltages, particularly when the voltages in question are largely unknown, and the consequences of errors extend beyond the price of the oscilloscope to the integrity of our laptop computer! I frankly find all this high voltage stuff daunting. My domain was uA, uV, and tens of Mohms -- electrical currents through glass electrodes of maybe 10 microns in dia, recorded from neurons a quarter that diameter. I rarely dealt with voltages higher than 15VDC.

Thanks, Zedyone! Yeah, those look good! I'll probably go the same route, then. You actually did shoot the angle I was more interested in seeing. I was curious how the slant of the sidewall would look, with a narrower tire mounted on a wider rim. I do slightly prefer the wider look, but only slightly. I certainly want to stop the rubbing! I see both the Grids and the Pole Positions (where do they get these names?!) look pretty good in the reviews. The reviews seem slighty better for the Pole Positions, but the Grids look sharper (to me). Decisions, decisions... Wow, your garage does look very nice! I think I see the corner of your Datsun logo in the lower left of the last photo. How did that work out? It also seems to be a very BIG garage, with two cars parked end to end. Much prettier than ours! Hey, kudos for the surprise dinner! I know she enjoyed it.

Zs Ondabrain might know better sources, but I can recommend marine-grade wire to you, which you can buy through sellers such as WestMarine. It's meant to stand up to far more abuse (heat, moisture, chemical) than automotive wiring. If possible, get the tinned variety of wire, which won't corrode like the bare copper. (I doubt you can get that in marine grade, though.)

Hi Kenny, The cap looks clean and appears to have very little use on it. That said, it might be at least 5 yr old, as it doesn't show up in the PO's service records (which were printed off for me by his former Nissan (dealer) mechanic. Not many miles on it, though. The distributor itself is new/rebuilt. I replaced it when I discovered the advance mechanisms were all frozen up and that there was a slight bit of play in the shaft. The reluctor got replaced with the distributor. I was hoping a new reluctor and tighter shaft would also resolve the tach double triggering (which I though might be attributable to double firing of the ignition system), but that didn't happen. My injectors are very old and indeed might be sticking or spraying poorly. Of course that's an expensive issue too. I've been running Chemtool B-12 through my gas from time to time (every few tanks) to clean out deposits that might be there (and on the intake valves). Cleaned/refurbished injectors are on my "next" list, if new ignition components don't resolve the problem. BTW, fuel pressure is normal, the exhaust has a normal (slight hint of gas) smell, and the plugs look normal. I'm continuing to work my way through the system. As I said, plug wires and coil first -- coil being a likely, not too expensive cluprit and the wires being rather old and not of a type I like. I already received and installed the new NGK wires. It runs a bit better, but the problem isn't resolved. I'll probably get the coil today or tomorrow and hope to see a miraculous recovery. Doradox, I really should have checked for continuity between the primary and secondary on the coil. I was in too big a hurry, with nightfall upon me. Ah well. Zcarnut, no problem. I'm not particularly "happy" with my test setup, but it's really all I have right now. As I said, I'm rebuilding. I haven't had much use for a test bench post-university, but there are a few specialized devices I would like to develop for my photographic work. Just curious: Do you have the schematic specifically for the Hitachi control unit in my '78 280Z (different unit from the '77)? I did a quick search for the two transistor types I found in there. I found reference to the power transistor on the heat sink, but no technical specs. I didn't see any obvious place I could buy a replacement, nor did I find cross-reference info. I also found nothing on the handful of little transistors sprinkled throughout the circuit. I feel as though I might be able to rebuild the circuit if I can find compatible semis. Thanks, everyone! Peace, Sarah

Just wondering: Is it possible for the secondary to have shorted to the primary? That could result in some crazy-high-voltage ringing in the primary trace. Hmmmmm....

Steve, I won't belabor my qualifications. I have them too -- not as good as yours, admittedly. I recorded this trace through a passive attenuator network -- garden variety, 100% resistive T-attenuators. No capacitors. No AC. Only DC. Irrespective of the properties of the attenuator assembly, and irrespective of whether it works properly or not, it's still a resistive network, and it still passes DC, not AC. Is it not possible that the clamping diode in the ignition unit has failed, making the negative swings not quite so impossible? That said, I don't remember seeing a diode in the circuit -- just resistors, transistors, and caps. Furthermore, negative voltage swings are indeed possible in oscillating circuits. I admit I'm stumped as to the magnitude of the swings, but I'm not willing to say they're impossible. A working oscilloscope and a pile of resistors say otherwise. I do appreciate your input, but I have to say I'm a bit put off by the tone. I wish I had a more impressive test bench, so that I could look smarter and more authoritative. Unfortunately two long distance moves and a divorce leave me with very little in the way of test equipment. I'm slowly rebuilding, hence the cheapo Chinese USB oscilloscope. I'll cobble together a proper 100:1 probe too, but for this measurement I simply grabbed what I had sitting around. Sarah,

Thanks, Zedyone!

Those badlands can be beautiful country, as you've apparently discovered! When I look at the pic of your Z in front of the canyon, adjacent to your signature pic of your Z in your driveway in Ft. Wayne, I feel as though it has rightfully earned the highest honor of "traveling machine." Naturally the machine's brave pilot deserves considerable credit too. ;-) Pedal braking vs. engine braking: Yeah, if you're going down a long, steep grade, downshift. You can probably just stay in the same gear for going up again. It's OK to spend all of your time in 4th in the hills. Brake overheating was more of a drum thing (as on your rear wheels), but it also happens on disc brakes. One of the maintenance hazards is warping the rotor or depositing glaze unevenly, resulting in vibration in the brakes and uneven braking. If your brakes do overheat/fail for any reason, just give the emergency brake a yank. It's actuated mechanically, not hydraulically, so it's not going to fail from overheating. Happy trails!

Zedyone, I have EXACTLY the same problem you did, with a rub on the right front tire against the forward lip of the fender when backing (but not pulling forward). I have the same Panosport rims, with Goodrich Comp T/A radials -- 215/60R15. I have probably half the original tread on the tires. The previous owner confirms that he experienced rubbing on occasion. I've been doing calculations, and I think I can pull in about another .3" of clearance with 205/60R15 tires -- approximately the same diameter as stock, but a bit more offset. Of course there's always the factor of the extra tread on a new tire. I'm thinking the 195/60R15 would give me another .3" still, but it would be about .25" smaller dia than stock. I'm just wondering what that looks like. I'd love to see a few pics, if you're able.

:stupid:Duh!:stupid: This makes me think I should install another relay on the parking light circuit. Is this a frequent problem? How about turn signals? I have an electronic flasher I'll be installing to offload some of the current, but the turn signal switch takes a lot of abuse.

If you install headlight relays, you won't have the melting problem. You'll also have brighter headlights. There are four tabs holding the switch together. You can carefully bend them back (not much!) and pull the switch apart. Be careful, as you will probably have an exploding spring or two. Once the switch is open, you should be able to determine pretty easily how it failed and correct the problem. You'll of course have to play that part by ear.

Hey Frankie, glad to hear you're operational again. I hope you had a bit of fun in Chicago to make up for the troubles in southern Minnesota. Good luck in your travels. Denver (next stop?) is a very cool place. Be sure to check out Boulder while you're there. (I wanted to go to UC Boulder at one time.)

Crazy? Nah.... Dogs love to drink, you know. I remember having let our dog out onto my stepson's patio the morning after he had thrown a party. About a half hour later, I found he visited all the drink cups that were left on the ground, slurping up any left-over beer. He also found a bag of corn chips. Now as for Z'aholics getting into the motor oil... That's another matter altogether.

I bought a car like that once -- an Olds Cutlass with aluminum foil stuffed in the fuse box and fifty gazillion wires twisted together. I assumed I could fix the electrical problems, being handy with electical/electronic stuff, but there was a lot more melted and trashed stuff than I bargained for. I learned never to buy a car like that. Of course that doesn't help. The good news is that you actually have 30 (inline) fuses. If it were my car, I'd completely rewire it. You can buy pre-made wiring trees. I've never bought one, but I suspect it would come with pretty good instructions as to what plugs in where.

Which wires are you talking about? Are you trying to solder or crimp-connect wires in the wiring harness? You can clean corrosion from stranded copper wire by neatly splaying the strands in a fan-like pattern, pulling them through fine sandpaper sandwiched between your fingers, regathering the strands, splaying in another direction, sanding, and then repeating with the strands splayed in yet another position (or two). Eventually you'll expose enough copper to solder (or get a clean crimp). An approach I've heard about but never tried is to use vinegar, which will supposedly dissolve away the oxidation and then evaporate when you're done with it. Another tip: You can crimp cleaned wires together inside a very small copper tube, and then fill the tube with molten solder. That will make a marginal connection much more solid. If you want a good alternative to fusible links, you might try MaxiFuses. I'm thrilled with mine: http://www.classiczcars.com/forums/showthread.php?t=35588

I was able to go through all the connections, and they were all beautiful. Not a bit of corrosion or dirt or any other indication of anything gone wrong. Taking measurements at the ignition module connector, I was able to confirm a healthy supply of power and good connectivity to the reluctor and the primary side of the coil. The coil's primary resistance did measure a bit on the high side, though -- about 1.3 ohms, vs. the .84-1.02 ohms that a new one should read, but still less than the 1.8 ohm reject level cited in the FSM. The secondary side of the coil measured about 13.5k, only slightly higher than the 8.2-12.4k specified on a new coil. I also opened up the ignition module to have a peak inside. Very pretty vintage circuitry, obviously assembled by workers who would have dishonored their families and company (Hitachi) by failing to line every mylar cap up perfectly perpendicular to the board. Nothing jumped out as obvious (e.g. scorch marks on any of the parts). There was one power transistor and several low-power transistors of the same type. Neither these two transistors nor their data were available on the Internet. Sort of expected, but.... drat! Anyway, it's not the wiring or connections. That's for sure. So I guess I'll start replacing parts -- first the coil. I also would like to have the NGK-type wires, so I'll go ahead and get them too. If I need to replace the ignition module, I've confirmed that an MSD-6A will fit the space on the passenger kick wall, and I can use all of the same wiring. I'm going to install an MSD Blaster 2 coil to match an MSD ignition module -- based on my expectation that the ignition module is actually bad. (The trace really wreaks of semiconductor breakdown to me. The oil in those power transistor cans sometimes leaks out, leaving the contents to bake. I suspect that's what happened.) From what I've read, the MSD-6A, the Blaster 2 coil, and the NGK wires are all a good match for each other. I guess this will be next weekend's project, depending on how fast the UPS truck gets here. Again, thanks for helping me with my ignition. I'll post back when I find out what was giving me that funky waveform.

Hi Ron, You wrote: Interestingly, I think there could be some similarities to electronic ignition. One possibility I've considered is that of inadequate current to the coil during the dwell phase, either from semiconductor breakdown or from crusty wiring. The weak tensioner spring might produce the same inadequate current. I'd love to have a peek at that waveform. Could you post it for me? Thanks so much! Peace, Sarah