FastWoman

Hi Steve, Oddly, I can't give an easy answer ot the voltage of the primary trace, but it's quite high -- I think I would say "hundreds of volts." Unfortunately the attenuator I used was something I cobbled together long ago, and I've forgotten its design parameters, other than the fact it has an overvoltage clamp to protect the oscilloscope. Also unfortunately, I have no way to test the secondary circuit. The voltages are WAY too high. I think I have some glass-encased resistors I might be able to use for that. Dunno. Anyway, I seem to have at least four things loosely corroborating faulty ignition: (1) an abnormal waveform (2) engine missing, especially under load (3) massive black sludge accumulation (previous post) (4) double-triggering of the tach during misfire. (Note: This problem occurred both with the OEM tach and with a modern retrofit tach board.) You suggest starting with the ignition coil, probably because it's the cheapest suspect. Plug wires would also be likely suspects, except that I've tested them, and they're within normal limits. My car did come with the advance mechanisms of the distributor seized up, so I have a new/reman distributor now. Rather than trying to track down THE compenent that's giving me trouble, would this be a good time to upgrade to a more modern ignition system? What are my best options for a '78 Z? Thanks so much! Peace, Sarah

Thinking about the article a bit more, some of what I've been experiencing makes more sense. My engine still misses quite a lot. The idle is somewhat unsteady, as though it had a very mild cam. Acceleration is somewhat weak, and it feels as though the engine is missing. Not having a very loud exhaust, it's hard for me to hear what the engine is really doing. Anyway, when a cylinder misses, the "burn time" of the spark is shortened, due to lack of combustion products. That results in an exaggerated ringing at the end of the burn time period, thereby double-triggering my tach. I get somewhat less than 1kRPM swings of the tach needle at maybe 2500 RPM on moderate acceleration, so that would mean maybe a third of the cycles fail to detonate -- essentially like running on 4 cyl, instead of 6. It does feel a bit like that. Question: When the ignition is weak, do the misses tend to occur more frequently under load? That's when my tach needle jumps around the most. At idle, it twitches occasionally. At higher RPM when not under load, the needle is pretty steady.

Thanks, Steve! The links were extremely useful. The article is a bit dense, but a very informative read. Now I think I have a better clue what I'm looking at. Missing in my screen shot is the time scale, which was 0.4 ms/div. The "false triggers" I thought I was seeing were simply the ringing at the end of the burn time. I hadn't included the time scale, but it'w 4ms/div. My burn time seems to be about 1.5ms, give or take, measuring by eyeball. The engine is spinning at about 2kRPM. The glitch maybe 3.5ms prior to the spark seems to be the beginning of the dwell period. I'm still not completely sure what I'm seeing; however, the burn time (with normally gapped plugs) is undeniably about 1.5 ms, which says something good about the total energy the coil is delivering through the plug. Perhaps the peculiarities with the waveform have more to do with my testing apparatus than the ignition circuit. I cobbled together a high voltage probe, with overvoltage protection, that would allow me to hook up my cheap USB digital oscilloscope to a high voltage source without blowing it up (along with the computer). I might start with a repeat of my diagnostics, after cleaning up terminals, establishing better probe connections, examining different voltage scales, and lastly, figuring out how to digitize/record maybe 10 or 15 revolutions in enough detail that I can see what's going on. That will let me look at what's going on in the individual cylinders. (Very cool.) Steve, if I do need a new coil, are the flamethrower coils compatible with OEM ignition? If so, it might be good to have the flamethrower coil, in case I needed to retrofit with a Pertronix Ignitor module. How are the Ignitor systems, BTW? It seems like a lot of high power circuitry in a little module, stuffed into a tiny enclosure (the distributor). It seems like it would be prone to overheating. Do these modules have a good service life? I really appreciate your help! Thanks! Sarah

Hmmmmm.... That MIGHT just be noise in the data stream of the digital oscilloscope, but then again, it MIGHT be the problem you describe. I'll need to scope the +12VDC for a better look. Hrumph! I just replaced the alternator last week. The previous one was a lifetime warranted unit that lasted a month before it quit. It's definitely connected VERY well from battery to block. Quality parts, eh?! Any thoughts about the ignition, though?

I remember when I first got my '78. EVERYONE was stopping me to ask about it. Then after a couple of weeks, that didn't happen anymore. I was starting to wonder whether it was because the same people had seen it or whether I simply looked more at home in it. Maybe the grocery store runs with paper bags just don't look as sexy. Anyway, yesterday was another day in which my Z got a lot of attention and misc. weird stuff happened. At one point on our rounds, our accountant asked to look under the hood and hear the engine. We talked about the car for a while. When we left his place and pulled up to the first light, up beside us rolls another Z -- same years as mine ('78), except red. What are the chances of that? He had cut off the top to make a pseudo-convertable. It looked really nice, but he had no rag top. Definitely a garage queen. We chatted a bit until the light turned gree and then parted ways. Off to the grocery store. The car had been running a bit rough, and I wasn't too sure about the re-start, but we needed a few items. Sure enough, when we loaded up and tried to start the car, it sputtered, coughed, died. The more I tried to start it, the more flooded it got. Perhaps I started out with a bit of vapor lock from the hot engine? Anyway, I popped the hood to let the fuel system cool down a few minutes, while holding the throttle open. During that time, another woman and her 11 yr old son came out. While she loaded up groceries, the boy stepped forward and just stared, arms hanging to his side, mouth hanging wide open. The boy looked like "Larry Mondello" from Leave it to Beaver -- even wore the same signature horizontally striped T-shirt. He stared, dumbfounded, for at least a few minutes, until I gave it a last crank and got it to chug to life and even out. Then I closed the hood, shrugged my shoulders at the boy, got in, and drove off, all with him staring at my car like it was a spaceship. (Perhaps it was the "backwards" hood?) I had to smile. I think that was the most unusual response my car ever got. I can imagine after we drove off that me might tell his mom, "When I learn to drive, I want a car just like that one." Then she would say, "You mean a car that doesn't run?" Ha! I spent much of today diagnosing ignition and emission control issues. Not as much fun.

Hi all, My second project this weekend was that I FINALLY got around to scoping my ignition. My engine still has a slightly rough idle (although at times it will smooth out beautifully), the exhaust puffs randomly (random misfires), I sometimes get a light backfire, and my tach needle gets these spasms -- twitching to higher values. At idle, the twitches are about 100 RPM in magnitude (with no change in engine speed), and on acceleration, the needle sometimes bounces wildly over a 500 to 1000 RPM range. Interestingly, the needle doesn't necessarily bounce wildly at steadily higher engine speeds. It's mostly when engine speeds are rapidly changing. So here's a trace of the (-) terminal of the ignition coil with respect to ground -- very greatly attenuated: I sort of expected to find random extra pulses from false triggers, not from slop in my distributor (which is new/rebuilt), but from a possibly faulty electronic ignition module. I didn't find that. The pulses ticked along perfectly with the engine. However, I did see some lower voltage hash between the pulses -- PERHAPS of a high enough voltage to false trigger my tach and PERHAPS jump a low voltage spark to cause pre-ignition. I also note, more significantly, that the waveform doesn't resemble the normal waveform drawn in the FSM, where there is a brief voltage plateau for each pulse, preceeded and followed by ringing. Neither does it resemble the waveform they show of a dying ignition module. I'm left wondering whether the abnormal waveform is because of my ignition wires (which are conventional carbon core) or because of the ignition module. The false triggers, if that's what they are, would seem to indicate a bad ignition module. Anyway, I would greatly appreciate input from anyone who knows what real-world ignition traces look like. Thanks bunches! Peace, Sarah

Hi all, I've FINALLY launched into troubleshooting my emissions equipment. Everything in the EGR system checks OK, except for one item I'm not sure about -- the thermal vacuum valve. It's the device with engine coolant running through it that supplies vacuum to the EGR system after the engine warms up. In the EGR INSPECTION section of my FSM (p. EC-13), it says: *Disconnect one end (BPT valve side) of vacuum hose connecting thermal vacuum valve to BPT valve. *increase engine speed from idling to 3000 - 3500 RPM *Make sure that thermal vacuum valve is close and that throttle chamber vacuum does not exist at end of vacuum hose. If a vacuum is present, replace thermal vacuum valve. Then warm up engine above 122 deg, and repeat test. This time, "if vacuum is weak or is not present at all, replace thermal vacuum valve." I read absolutely no vacuum up to about 1/3 scale on my temp gauge, which is as it should be. Above 1/3 scale, I do read a vacuum, but it is only about 5-6" Hg -- well short of the manifold vacuum. But then I consider that the vacuum takeoff is somewhere in the throttle chamber, so it could be almost anything, depending on where the tube opens in the chamber. So what is a "weak" vacuum? I wish they had provided a number. Is 6 in Hg "weak?" Is my thermal vacuum valve operating within normal limits? Thanks! Sarah

Thanks for the photos, Andy! For me, the really fun ones were the Toyotas. You took pics of a couple of nice mid-70's Celica GTs. My first car was a 75 GT. Sort of underpowered, but I enjoyed it. Then there were the 2000GTs. Ooooooohhhh, baby! I agree about the collectable aspect of our Z's. I think they've gotten no respect in the collectors' world because of being foreign. (Not even old Porsches have the collectable value of classic American cars.) I think that's disappearing with the emergence of new generations of collectors. At least that's the bet I'm making with my own Z. My Mustang was a pretty good investment (certainly much better than any of my RESPONSIBLE investments), and I expect my Z to do even better over the years. Time will tell.

FAIW, I listed my '66 Mustang very recently on Craig's List and got my (firm) asking price of $1000 under the appraised value ($1000 less, per the advice of the appraiser). There was no bickering. He was happy to get it. Perhaps it's something to love and tinker with during the winter, in anticipation of the spring. Anyway, it's free to list, and I've racked up three very good auto sales so far on Craig's List. People ARE buying now. I would just make it clear that you're not going to let anyone test drive the car in the snow/salt.

If the overspray is a non-polymer variety of paint, you might be able to clean it off with mineral spirits. Mineral spirits will also dissolve away oxidized rubber -- if the part is rubber, and not vinyl, and that will make your rag very black very fast. No worries.

An inline check valve is readily available. For instance: http://cgi.ebay.com/ebaymotors/One-way-Check-valve-for-Gas-or-Diesel-fuel-5-16-Bio_W0QQcmdZViewItemQQhashZitem27ac74820fQQitemZ170397041167QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories (Ebay seller jbass195) (I'm pretty sure I remember the nipple being 8mm or approx 5/16". If that's not the right size, he also has 3/8" and 1/4".) Still another solution would be to wire in a switch to actuate the fuel pump relay. Press and hold for 10 sec to prime the fuel rail, and then start the engine. My current plan is to pick apart my Nissan check valve and to replace the guts of it with a new ball bearing and spring. I might have to dress up the mating surface too. Then I'll set it aside to replace the Volvo valve if/when necessary, repeat, repeat, until fuel pump dies. Then I'll be using a different check valve anyway.

Yeah, I already know all about reddat. I bought several parts from him in the beginning of this project. I did ask him up front to quote me combined shipping charges, so I don't think I got the short end of the stick on anything. That said, I don't think I would be likely to do business with him again. Among other things, I was far less than impressed with his packing. Anyway, I can see it now -- Genuine Nissan fuel pump check valves with barbed nipples. Rare! A must for your restoration! I REALLY would like to see an aftermarket source surface for this part, 'cuz this sort of hoarding practice is really sleazy. BTW, the ultralight aircraft guy just told me he isn't interested in taking on another big project (check valves). Ah well.

... so I've contacted this guy who makes check valves for ultralight aircraft, and I've pitched the idea to him of making aftermarket check valves for 280Zs and early Volvo 240s. Think positive thoughts, everyone!

So can these precious little check valves be refurbished?

So it seems good deed goes unpunished. I thought I'd share my findings here on this forum, so that others in need of check valves would be able to source them. Stupid me. :stupid: Now somebody reading this thread has apparently gone and bought up all the Volvo 240 check valves, which are out of production. (reddat?) I tried to carry out my usual practice of ordering a replacement part, plus an addition item as a spare. I'm being sent one part, but am being refunded my purchase of the second part. Everyplace I've called/emailed is out. Thanks a whole lot, Mr. Profiteer, whomever you are!:mad:

Aw, Frankie, I'm sorry to hear about the delays. I hope you're at least having a good time in Chicago. I've passed through there a few times and never had time to stay. Looks like an interesting place. Just out of curiosity, did you check out the resources in the little town whose name shall not be mentioned to see if there was anyone who could rebuild the transmission you already have? It might be a real mess, but then again, someone might be able to save it. My mom used to live in a similarly tiny town, but there was a good mechanic there who I think might have been up to the task. (Maybe you should have packed your transmission on the bus to Chicago. Ha!) Anyway, good luck getting all this sorted out. Do keep us posted, including on the fun things you're doing in Chicago. You may not realize it, but you're living out a very interesting story -- at least from where we're all sitting. Peace, Sarah

I was wondering the same thing, Tomo. I don't know. (I won't be back under my car for some time now.)

Hey, has anyone put together a database of commonly available alternatives to Nissan NLA parts? If not, shouldn't we (as a community) do this?

Tomo, I'm getting the Volvo part -- substitutes for the OEM Nissan part. Had I gone with an inline check valve, I would have pulled, gutted, and replaced the original check valve (i.e. making it into a nipple with no internal parts). Hey, how long do these things usually last? The check valve on my '75 model lasted at least to 15 years, at which time the pump died. However, the car was always hard-starting for reasons I didn't understand. (Maybe the check valve was bad?) I replaced the pump with a new Nissan pump, and it lasted me the 5 years until I sold the car. Anyway, I bought two check valves -- one for a spare. That should probably last me until my pump dies.

Ah, you posted while I was posting. Yes, it looks like it should work fine. I'll post back when I have the thing installed. Thanks again! Sarah

Here it is: http://www.fcpgroton.com/product-exec/product_id/5140/nm/1976_1981_Volvo_240_Fuel_Pump_Check_Valve/category_id/151 Nobody was able to pull it up for me via the Bosch part number, aside from a local import parts specialist. He knew what it was but couldn't get it for me (not in his store or anywhere in his parts network). He wasn't able to cross back to tell me which volvos it fit. So it was back to Google. Apparently we're in good company with the ubiquitous Volvo 240, 1976 - 1981. I have a couple of check valves on order -- one as a spare. Unlike the check valves I had previously linked, this check valve has a hose barb on one end. That makes more sense. Peace, Sarah

Never mind. I googled the part number you gave me and found my answer on zcar.com: The post was with respect to an '83 ZXT, but with the same part number nonetheless. Thanks for the part number! That was the key info I needed. (Ain't the Internet wonderful!) Peace, Sarah

Hi Steve, Thanks for getting back with me on this. Here's Bosch's check valve. The listing at the top is for the 1978 - 1996 Porsche 928, but the same part number refers to all engines for a multitude of years for both Porsche, Mercedes, VW, BMW, and Audi. http://www.thepartsbin.com/repsite/bosch~fuel_pump_check_valve~reparts.html I see on the same web site (links at bottom) that Bosch made check valves for Volvo and Saab, but those have different part numbers. Do the any of these look like your used one? (BTW, thanks for the offer of the used one, but I hate using used parts unless new ones can't be found.) I suppose I could pull the check valve and head over to one of the German dealerships to see what they might have that would match.

Hi all, The check valve on my fuel pump has been getting less and less reliable, and it's probably time to replace it. However, these little items are in very short supply, commanding a very high price. Question 1: Are there any aftermarket sources for this item? Question 2: Has anyone tried inserting a generic inline check valve, perhaps in the vicinity of the fuel filter? Did that work well? And if you did this, did you insert the valve before the filter (so that any debris from a failed valve would be caught by the filter) or after the filter (so that any pumped debris wouldn't compromise the functioning of the check valve)? Thanks! Sarah

It DEFINITELY runs on 12V. Check the running voltage to make sure it's adequate. It should be no more than 0.5V less than the battery/running voltage. Potential problem points on the '78 are (1) fusible link, (2) fuel pump relay, (3) large connector just inside firewall on passenger side. I had recurring problems with #3 -- caused by corrosion, resulting in arcing and melting of plastic. I eventually snipped that one wire from the connector and replaced with a bullet connector.