Captain Obvious

Thanks for the additional suggestions guys. One other thing my "plan" provides is reducing the overall width of my spare. The accordion spare is on a 5" wheel and pretty much bumps against the underside of the false wood floor. And believe it or not, but because of the significant offset difference, the space saver wheel (the one that fits the rear but not the front) bumps up against it as well. You would expect the space saver to be narrower, and the rubber portion is. But because of the offset built into the metal portion, the overall width is about the same. Moving that space saver rubber to a narrow Z wheel will allow me to drop the height of that false wood floor and gain some valuable space back there. Of course, a can of fix-a-flat is thinner yet, and a AAA card is thinnest of all!

Before I forget though... It's clear that the two ECU's are from a different run. On mine the feedthrough wire connections are labeled "U sub n" (U1, U2, U3...) You can see U9 and U15 on mine for example while sscanf's are not marked in any way. It's clear that the silkscreen markings of the two different boards changed along the way, and I can tell you from experience that nobody changes just the silkscreen. It's too expensive. I'm sure there are some copper changes somewhere between the two as well. Might not be extensive, but I'd bet good money that something changed.

What makes you think the resistors are any different? But before you answer... The fact that mine have a gold stripe on the end while the ones that sscanf posted have green and blue? Take a look at the other end of the resistors in sscanf's pic. Mine were just assembled the other direction. No difference, just mechanical 50/50 pseudo randomness. So if that's what caught your eye, don't worry about it. Direction on the resistors makes no functional change.

Thanks for the info on the space savers, but that's not the real problem here. Let me put the whole story out there... First, let me start off with: I did get my hands on a 4.5 inch wide Z rim, so if anyone is still looking for me, thanks for the help and I'm calling off the dogs. Now back to the story... I have a 77 280 with the collapsible accordion spare and the inflator bottle. I don't trust it. I don't know if the bottle has anything in it, and I'm not sure that accordion spare would be all too happy to be woken up from a 40 year long slumber. So, with all that in mind, I started looking into different options instead. Problem number one... I don't have enough room to use a full sized spare. The spare tub in 77 is too small of a diameter. A full sized tire won't fit down in the small tub. I don't know when exactly they made this change, but I know a 74 will accept a regular tire and wheel combo, and 77 will not. So in either 75 or 76 they reduced the size of the spare tire tub and made it necessary to use the smaller accordioned inflat-o-spare. So, I went to the junkyard and started looking for mini space saver spares. I found lots of them with the proper lug pattern (like your list above), but the diameter restriction is an issue even with the space saver spares. I took a tape measure with me and bought a 15" space saver with a diameter that should fit. When I got home I pulled on front and one rear wheel and checked fitment. Fit fine on both front and rear. Offset was wrong, but I didn't really care too much. Like you said, it's temporary only and emergency use. Offset isn't really a big deal. However, as I was test fitting the 15", I realized it had very little air in it and as I filled it properly, it grew in diameter and when done, it wouldn't fit in the tub anymore. Duh. So 15" doesn't work. Back to the junkyard and picked up a 14" space saver with the correct bolt pattern. It's a 115/70/14 and even when fully inflated, it fits in the 77 tub. But when test fitting to the vehicle it highlighted problem number two... It fits fine on the rear, but in the front, it won't clear the caliper because of the shape of the back side of the wheel. :tapemouth So, the bottom line is that I'm not sure there exists a space saver spare that will fit in the reduced diameter 77 tub while still having a large enough wheel insides to clear the front caliper. That brings us to now... I've got this 115/70/14 tire that would work just fine if I moved it to a wheel that would clear the front caliper. The space saver rim is 4" wide and with the very short sidewall on the space saver rubber, I doubt I could stretch it out to a 5" wide Z rim. But I DO think I could get it onto a 4.5 inch Z rim. My theory is that a 4.5" Z rim with a 115/70/14 space saver spare tire mounted on it will fit the 77 tub AND will be able to be mounted to all four corners. And if that 's not all!! A bonus would also be that the offset would be appropriate. And that's the whole Alice's Restaurant Massacre as to why I'm looking (was looking) for a 4.5" Z rim.

The cold start valve is completely independent from the ECU. It's driven solely by a couple relays and the thermotime switch. I'm betting your ECU is stone dead and you're running off the cold start spray for a couple seconds. And for testing purposes, you don't need a Schottky. Any diode capable of handing the current requirements would work just for a proof of concept test. If the 1N4005 (I'm assuming you meant 1N4005 and not 1N005?) didn't work, you've got problems more significant than just the diode. No surprise there.

There used to be a shop close to 95 in the Baltimore area (north of Baltimore?) that specialized in 300ZX stuff. I can't remember the name though, so I know that doesn't do you much good. :stupid: But as mentioned above, Bernie should be able to hook you up. I sold my 94 to buy my 77.

Woof. That's not good... That used to be diode D190 and based on where it's located in the circuit schematic, I'm guessing it's a Schottky. Supposed to look like this: It's the main power feed into the ECU and the input side is hot any time the fuel injection is operating. I'm thinking reverse polarity protection for the whole shebang because it's in right at the supply input and feeds just about everything. So... Yours passed way too much current and went up in smoke. Problem is though... What was it that was demanding so much current that the diode gave up? The diode probably isn't the underlying problem, it's probably just the result of the underlying problem.

Hahaha!! Oh, the confusion!!

The transistors are easy. They're your garden variety 2N and 2S stuff. Problem will be that the whole box was "tuned" on an ATE fixture at the factory with those piggyback resistors. Who knows what parameters of those transistors have been characterized in that way. Gain, leakage voltage drops... Who knows! And there's the three IC's. Custom parts with zero documentation made out of unobtanium. :-) Good luck. We're all counting on you. PS - Haha!!! Hope you don't mind if I steal that one!

Absolutely! And if there's anything I can do to help, I'd be happy to!

What are the big red things? Same as the small red things. Film caps, probably polyester. Just higher value or voltage, or both. Good luck with the poking around and let us know if you see anything suspicious! On edit, forgot to mention... I'm surprised as well about the lack of electrolytics. I fully expected to find at least a few in a power supply section or something, but I really don't think so. Credit to the designers! Also, video game repair? Cool! That's one of the things that got me through college. Classes during the day, game repair in the evenings. Always had to earn the next semesters tuition!!

http://www.classiczcars.com/forums/engine-drivetrain-s30/49675-weak-return-center-spring.html

Thanks for sway bar input. The end link bushings have to (by design) deal with significant misalignment in every direction other than vertically without loading the bar. Side to side, front to back, they just swivel on the bushings accordingly. Every direction other than vertically shouldn't load the bar. So I'll just count my lucky stars that my sway bars line up almost perfectly vertically. When I put mine back in I was able to tighten up the frame mounts and then just rotate the entire bar in it's mounts until the end link holes lined up. No muss, no fuss, not fight. And I've done it the other way as well... With the end links still attached, I am able to remove and reinstall the frame mounts without any fight. In other words, I didn't have to wrestle or force the frame mounts to get the four holes lined up. They just aligned naturally and the bolts slipped in and went finger tight all the way to "home" without fighting preload. It wasn't like I had to squeeze the second mount into place after tightening the first. They just lined up. Hanging or loaded, same results. I'll watch over my shoulder for Murphy to catch up with me as well? Sounds like maybe I owe him one?

Take a look at #6 as well. I don't like the way the head gasket has slipped off position and is out of round near the water jacket. Did you do a compression test before you pulled the head?

I've poked around a little with the board, but nothing significant. I didn't find anything that looked even remotely unhappy. One thing I can tell you is that I've not seen any electrolytics used at all. So I'm not sure I'm buying the "drying out" theories. Granted, I've been inside a whoppingly huge number of "two" though, so take that with a grain of salt. I remember the big resistors of which you speak, and IIRC they are just input protection for some of the sensors. Low value and low current. If you're really curious, let me know and I'll refresh my memory. Troubleshooting to fix long term drift? Not me!! Not without Robert Bosch on speed dial!

Thanks John, I'm not a suspension guy at all so bear with me a little. Here's my thoughts on the sway bar. The sway bar is a spring, but it's used in torsion. Torsion which is developed only when one wheel is higher than the other. If both wheels are at the same altitude, there's no torsion. As long as both wheels are hanging at the same altitude or both wheels are loaded to the same degree, it's the same thing to the sway bar. Neutral. No preload. Said a different way, if you attach both end links with the wheels hanging and then put the car on the ground, the ENTIRE bar (both ends, AND the center portion... Everything) will simply rotate in the two frame mount bushings as the suspension is compressed. But there will be no torsion at any time. Am I missing something?

One establishes baseline for the rubber bushings by loosening up the center lock bolt while the suspension is under load and allowing the rubber to relax to thier natural un-stressed position. Loosen the lock bolts, "jounce" the suspension a couple times, maybe push down just a little (unless you've got someone to sit in the driver's seat for you), and then tighten the lock bolts. This is all because of the way the rubber bushings work, and especially important if you've done significant suspension work or lowered your car. You don't do this to assure they're not stuck... You have to assure they're not stuck in order to do this. (Does that make sense?) If the bushings are rusted into place, they will not normalize. The inner sleeve must be free enough to rotate to it's relaxed position and it won't do that if it's stuck rusted in place. What you're trying to prevent is having the rubber portion of the bushings under any rotational stress while the car is under "neutral" load sitting still flat and level. When the car is neutral, you want the bushings neutral. This is the theory behind the requirement in the FSM that you load the suspension before tightening up the suspension points. This requirement only applies to the control arm pivot points though. T/C rods and sway bars don't care. Tighten them hanging or loaded, no difference. I whipped up a couple sketches of the control arm bushings that show the theory of how they work. Here's a front bushing: Here's a rear inner bushing: And here's a rear outer:

So anyone know anything about the Roadster steelies? Through on-line digging and reading, I think I have verified that they are 14" and have the 4x4.5 lug pattern, but what about wheel width and offset? Anyone know?

Thanks Dan. I've got feelers out in a bunch of different directions, but at this point, yes... I'm still looking. So if you get the chance to peek up in the garage attic, measure what you have. I've already got a 5" wide, so that won't do anything for me, but 4.5 or even 4.0 would be great.

Still hunting for a 4.5 inch wide Z wheel and not making a lot of progress. Thinking that maybe I could open my field of interest a little? Are there wheels from other cars that might work? For example, what about Roadster wheels? Anybody know the specs? Are they 14 inch? Same lug pattern? 0 offset? Early 4 1/2 wide Z steel wheels - 40300-E4100 Roadster wheels - 40300-14600 and 40300-14601

Very nice. I'm going to have to think about the geometry of this method. Hey, did you re-establish baseline on your control arm bushings first?

Awww man..... What the heck??? :ogre: Murphy must really be pissed from that sheet metal screw thing in the rear. Time to reset that two trouble free weeks counter!! Was there some specific event that preceded the failure? Been quite a while since I did a head gasket on one of these, but if you've done others, this one is pretty simple. Don't snap off the bolts holding on the thermostat housing and don't drop the timing chain. Oh, and when you're yanking the head up and it just won't budge like you missed a bolt somewhere, don't forget about the small one (or two?) around the front cover.

Yeah, what he said. And Murphy is probably looking for an opportunity to get even. I'd watch your back if I were you... :paranoid:

Cool. Another crisis averted. My experiences are that as long as the fuel pressure holds long enough to crest the hot shut-down hump, then additional time is nice, but not required. An hour should be enough. But what the heck? Now the radiator? Can you please get a two week trouble free stint out of that car??

Right. I should have mentioned that it depends on the internal design of the gauge. My gauge was pretty cheap as well, but it was a Bourdon tube style and had an internal linkage that involved gears. You can go another level cheaper to gauges that don't use a Bourdon tube and are a direct drive style without linkage. Your cheapo Chinese is probably that ultra simple design. So by going that cheap, you accidently lucked into a design better suited for the application. I made the mistake of using too good of a gauge on mine and paid the price.