Paulytunes

...and after a ~20 minute test drive, everything seems operating as it should. Now on to resolving the known issues and corrections.

Well, I had some time this morning, so I bypassed the resistor. That seems to have done the trick!!! No more stalling after a high RPM pull. Thanks so much for all the help! This forum is awesome!! I am going to go for a morning test drive to verify.

All testing since the module swap has thus far been in the garage with the Z parked and handbrake on. Test procedure has been as follows: Reconnect negative battery terminal. Start the car and let it warm up. Once idle normalizes around 800rpm, apply throttle and observe. With the HEI module, when I rev past 2000rpm, the tach needle drops quickly to zero and the car stalls - this happens quickly, like the system gets overloaded and shuts itself off. Restart is only accomplished by turning the key and re-engaging the starter.

Chas, Thanks for the suggestions and your excellent write up that got me this far. The blue wire is attached to the end terminal on the resistor. Should I try and bypass the resistor and connect straight to the coil? I will also look into trying to adjust the reluctor air gaps. To add insult to injury, I opened up the hood to find that the condenser wire was broken. Old and brittle, I guess they do snap. I doubt this is contributing to the issue, but I guess I will be shopping for a new one.

Update: So I went ahead and replaced the coil and swapped out the TIU with an HEI Coil. I followed EuroDat's instructions but modified it (see the photo of schematic wiring diagram). The HEI is a Petronix D2000 and the coil is a Petronix Flamethrower 0.3 ohm. I was very reluctant to cut the wires on the TIU, so I also bought a terminal block from Lowes and mounted it to the TIU box. I finished wiring it up today, reconnected the battery, said a little prayer and started the Z up. I let the engine warm up and idle seemed to smooth out around 800rpm. The issue that I am having now is that when I apply throttle, and anytime I exceed 2000rpm, the engine immediately stalls. It starts right back up again, but the problem repeats. I tried swapping out the red and brown wires to see if that would make a difference. The problem is the same. Could I have messed up the green and red wires? Or should I have bypassed the resistor and wired straight to the coil? I am also toying with putting the old coil back in to see if there is any difference. I took off the distributor cap, but I did not see anything odd. Any advice or tips? Thanks in advance for any help.

So far I have not found the smoking gun, but I am really toying with replacing the coil and doing the GM HEI mod to bypass the TIU. However, I am a little hesitant to try to wire it up, as it seems the 1976 TIU is different than the one in EuroDat's excellent instructions, which is based on a 1977 model. I guess back in the 1970's and 1980's the changes from MY to MY were substantial instead of minor and cosmetic like they are today. As you noticed, the coil looks pretty well aged. I'm not sure if it is the original coil, but maybe it is a contributing factor. I think one of my next steps will be to test the coil according to the FSM. It is not hot to the touch after driving.

Out of the times I have driven it, the only time that I did not have the car start to stutter was a trip under 10 minutes in total duration. The issue is recurring almost every time I drive it and until I get this resolved, I am gun shy of driving the Z anywhere more than a few miles from home. Trip 1 was driving it home from the mechanic where I first noticed the issue. Detailed in my first post above. Trip 2 - this was after I had replaced the fuel filter, and thought maybe that was the issue. The problem occurred around twenty minutes after driving, shortly after a full throttle acceleration from a rolling start to about ~50mph. I was able to limp home and kept the rpms under 3000. Trip 3 - I took my Dad for a ride to Lowes after going through all the fuel vents, about 6 miles roundtrip. Stuttered on the way home, probably at around the last mile of the trip. Limped home again. When I tried to start it immediately afterwards, noticed idle was rough and it wanted to stall, but would restart. Trip 4 - Took a friend on a drive to Costco (5 miles), no issues on the way there. Did one full throttle pull, similar to trip 2. When we were going to come home (after about 20 minutes stopped), the Z would not start after multiple attempts. This is what made me think it had to be a fuel issue. I had to get a tow home b/c I didn't think to just let the car sit for about an hour and all would likely well again. Of course, once home and the tow driver had left, the Z started immediately and I got it back into my garage. Since the tow, I really have not driven it (due to my paranoia that I am going to get stranded again and also due to the fact that we went on vacation). I've done some troubleshooting in the garage and driven around the neighborhood.

I did get a chance to do more today. I reconnected the ground at the AFM. The BCDD was connected to another wire which came out of a harness that included the connections for the water temperature sensor. When I disconnected the BCDD plug and connected it to the yellow plug, the idle ramps up to 2000 RPM and stays there. Maybe this was a connection meant for the A/T equipped cars? I figure the BCDD was connected to where it is supposed to be so I just put it back where it was and idle speed returned to normal, around 800 RPM. I did also take the Transistor Ignition Module apart and visually inspected. I wasn't able to see any bad resistors, but then again my eyes are 48 years old and getting worse with age, and I am a mechanical engineer that knows only enough electrical to be dangerous. Here are a few photos. The only thing that I did notice was that on the back side of the board where the soldering connections are, the one side of it seems to have a lot more blemishes or bubbles. Not sure if that's a sign that the board is bad or if it is nothing.

Update: so after some late night reading of the FSM, I found on p.BE-95 that the yellow wire is indeed supposed to be connected to the BCDD. The black wire is supposed to be connected to the ignition coil external resistor positive terminal. I will connect these soon and report back. I doubt this could be the root cause of my problem, but I do not think thses should be disconnected and hanging free and dangling in the engine compartment.

So I finally had a chance to do some troubleshooting today after coming back from a family vacation. I didn't find anything odd with the transistor ignition unit, looks to be in good shape and younger than 47 years. Getting ready to test it, but do I need to fully disconnect it to test resistance? The FSM says in the first paragraph to disconnect the battery and remove it to test, but then says to turn the ignition on (assuming with it removed or not connected and check using the multimeter). Sorry for the likely stupid question, just not following exactly how I should go about testing it. I don't have an oscilloscope, so I would only be checking voltage, resistance, and continuity with my multimeter. I did find two disconnected wires in the engine compartment, near the ignition coil. The first is a yellow wire originating from Engine Wiring Harness #2 with a bullet end connection. I'm not sure why the P.O. would have left this disconnected? It is shown on the second photo, near my index finger. My best guess is that this is supposed to go to the BCCD or the water temperature sensor if I am reading the 1976 wiring diagram correctly. I think it is the former and not the latter based on the length of the wire. The second disconnected wire appears to be a ground connection for the small device attached to the ignition coil mounting bracket in the third photo. Can anyone tell me what this device does? Is this stock or aftermarket? I don't see anything in the FSM showing this device, but I might not be looking in the right section.

One thing I did just notice, is that it seems to take a long time to get back to idle once revved up beyond 3000rpm. Other than that, no odd tachometer operation.

Zed Head - good idea, I will update my signature. It's a 1976 280Z 2+2. Tachometer operation seems normal. The car is still relatively new to me, so I don't perceive that it is reading incorrectly. I did notice that it bounces around after it tries to return to idle once I apply full throttle and it starts to have the misfires. I may go and try to test and watch the tach to make sure there's no crazy needle operation.

No, not absolutely sure, I figured fuel delivery was the first place to start. I'll look into the ignition next. He did not mention that there were any issues with the fuel tank, but I will need to confirm. He did ask me to check the ignition coil to see if it was hot to the touch after driving it. As far as I could tell, it was close to ambient temp. I cannot very easily take it back to him to evaluate since he's over 30 miles away and I certainly do not think it would be safe or feasible to drive it there. As far as the rubber hoses, they do not look very new. I would have thought the P.O. would have replaced them when the engine was out of the car and under his restoration performed but maybe not. I will replace them so that I am sure of when they were new and eliminate the potential worry.

Siteunseen, Thanks! the pre-filter seems like a great idea and cheap insurance to ensure the crap in the tank gets captured before it makes its merry way to the engine fuel filter, or worse, to the injectors. I did try to squeeze the supply line while the engine is running, it is very difficult to squeeze. My next step is going to be the Fram fuel filter at the tank. Hopefully that resolves my problem. If not, I guess I will continue troubleshooting. I'll update once that is completed. Paul

So here's my story. I bought this car back in late April, as a running car that needed some work, including a fuel sending unit. According to the seller, the engine was rebuilt about 6,000 miles ago and was in good running condition prior to the sale. The car sat at my mechanic's shop for about a month while the correct fuel sending unit was ordered and delivered. I picked it up about a month ago when finally completed. On the drive home, about 20 miles in, or just as I was 3/4 of the way through the Harbor Tunnel, the engine started to misfire and sputter when I gave it gas and above 3000rpm. I was able to get it to my exit by driving gently and keeping the engine speed below 2500rpm, until I reached about 30 miles in (or ~35-40 minutes of driving). Then all Hell broke loose, the car stalled repeatedly and it was a challenge to make it the last few miles home. I eventually did. When I started it about two hours later, all was well and you never would have guessed there had been an issue. I did notice the gas cap was extremely tight, enough that I had to tap it with a rubber mallet to loosen it. One suggestion I received was to drill a small hole in the gas cap as it may be a venting issue. I didn’t want to do that, especially after researching and finding that replacement caps for MY1976 are ~$200! I researched and thought this could be a venting issue, so I carefully removed the rear trim and cleaned the vent lines, checked the vent/expansion tank, and all seemed to be in order. The charcoal canister appears to be operating properly as well. I also replaced the fuel filter in the engine bay, as well as the fuel oil supply hoses. The above did not solve my issue, which has been getting progressively worse. On the next drive, the issue happened again between the 20 to 30 minute timeframe. The next drive it seemed to happen more quickly, say around 20 minutes. I took it for a short drive, ~10 minutes, 4 miles last Tuesday, parked it for about 20 minutes, and it would not start. I had to have Hagerty tow me back home, and of course, it started when I tried it again at home to put it in the garage. I did some research here, online, and consulted my Factory Service Manual, as well as talking to a few engineering friends. One is convinced that I have sediment in my fuel tank that is causing a blockage, which I made worse by performing a full throttle acceleration. From online research and others who had a similar problem, as well as the FSM, I started troubleshooting the EFI computer pins and Air Flow Meter. I pulled the AFM last night, and tested it, thinking a had a bad temperature sensor (pin 27). I figured that was too easy and I shouldn’t trust my cheap Harbor Freight multimeter, which I suspected had some issues when I was fiddling with it last night. Today, with a new and higher quality multimeter, I found I was correct and my HF merch is suspect, my AFM is not. So, I put it all back together and tried to see what would happen if I let the car warm up and then applied throttle while the Z was parked and took video (see attached and link below (if attachment fails to load)): https://youtu.be/vDj18VLJOvg Anyone here have this same problem and know what this could be based on similar experience, my description, and as shown in the video and noises? The squeal when applying full throttle isn’t normal, is it? I also noticed that when I gently squeeze the fuel return the idling seems to smooth out. I’ll keep troubleshooting in the meantime. I guess what I find out it isn’t will be verified to be in working order. Thanks in advance for any help, Paul 20230702_163448.mp4

Agreed. My daily and my wife's minivan get serviced every 5k miles and will likely have a similar plan for the Z. I probably should invest in a battery tender too. I've been reading through some of the threads on here and going through my FSM to try and diagnose before posting anything. I figure I cannot be the first person to have this issue and I stubbornly want to try and see if I can figure it out myself. I've heard a lot of different ideas like bad gas, rust in the fuel tank, clogged vent lines. I think I can rule out the vent lines, as my son and I carefully pulled out the rear trim and made sure all the vent lines were all free of obstruction. One curious thing I did find was that after the first time the stuttering happened, the fuel tank cap was ridiculously tight, enough that I had to gently hit it with a rubber mallet to free it. Tonight I pulled the AFM and I think I may have found that the air temperature sensor is bad. I cannot get a reading from my ohmmeter for pin 27 (p.EF-52). As I told my wife, this is a father and son bonding and educational experience, which should justify these added costs. I do wish I could make my garage a little bigger or at least tall enough to accommodate a lift. Thanks. I know these are a PITA and will likely require some tool purchases. I'll certainly be going through the FSM to test and see if there's any way to adjust and/or rule out if they are shot before replacing. It does sit a little low in the back and I hit the damn exhaust pipe on the more poorly maintained roads around here that Baltimore County or MD chooses to neglect year after year. My inspiration was a 2+2 I saw at Carlisle Import Nationals a few months ago, I also think I really like and want the rubber rear spoiler. I think that's a show winning car. I've looked into the Retrosound radios, which are a cool idea. Is this different? I think I need to research this a bit more. The speakers are original, but I think I need to perform some rewiring to get them to work. I found what looks to be a rodent nest behind the right rear plastic trim and the right rear speaker wires were chewed up to the point of nonexistence! I think he was looking at the washer tank and was fascinated that the pump was located on the bottom of the tank. Although he did as me about the brakes shortly after I snapped the photo, so he could have very well been looking and thinking about them at that point in time. Yes, I am sure PJ will want to learn how to drive it and will likely want to drive it as soon as he is able. I think if I do let him take it out, I will either need to have some sort of intricate surveillance equipment installed or I will just be on pins and needles. Of course, he will need to learn how to drive stick first, but I am certainly not going to let him learn on the Z! Thanks! I certainly will be posting here. This seems to be one of the best Z forums online. I am not really into the short attention span reddit sites or Facebook (which to me is a tremendous waste of time spent keeping up with the Joneses). Forums, however, are a tremendous resource, especially for classic cars. I hope to contribute as well as learn a lot here.

🤣 That's the main reason I got the Z. Imparting my knowledge to my son should also help keep me on my toes, he asks questions non-stop and has a neverending curiosity of figuring out how things work. He's become quite the mechanic's assistant. The Z needed a few things, as no 47 year old car is going to be perfect. Speaking of which, thus far it has needed a new fuel sending unit, speedometer cable, a new wheel stud and lugs (one on each wheel), battery, and fender resecuring, all of which were performed by the mechanic that performed the inspection. My son and I found that the car didn't have a windshield washer fluid tank, and it needed an oil and filter change, as well as a new fuel filter, so we have done that. It has developed a recent more pressing issue with fuel delivery. The Z runs fine when started cold and warmed up, at least until a significant load is applied and then it begins to drive really rough, eventually stalls, and needs to sit for a long length of time before restarting and is ok to drive again. I will likely ask for help in the technical threads, as I have tried to troubleshoot but it has been driving me insane. As far as long-term plans, I may get it painted (it was once already in the 1990's, but it is showing its age and wasn't the best quality). When I do that I will likely need to get two new front fenders, as these have some rust and Bondo. I'm also not in love with the likely period correct 280Z decals and pinstriping on the lower sides. I think it's also going to need rear shocks. The P.O. also planned on replacing the rear drums with discs, and included the discs in the sale - this and the shocks may be my winter projects. Some Panasport rims and new tires would also be nice. The current 8-track stereo is non-functional, which I may just remove and install a blank panel. With the stock speaker locations and the loudness of the current exhaust (may also be a future change, my mechanic referred to it as a "cheap muffler" and the pipe is noticeably the lowest thing on the car), I think I would be better off using my phone and a nice bluetooth speaker for music. Once upon a time I was into installing stereos, amps, subs, tweeters, mids, etc., but I think there are now far better things I can do with my money. Paul

Thanks to all for the kind words! I posted a build thread here to document progress on my Z:

First, a little history about me and why I love Z cars: Ever since I was a little kid, I have always loved the Datsun Z car. My uncle had a 1970 Datsun 240Z that provided many fond memories. I always told him, “If you ever sell this, call me, I will buy it from you.” Unfortunately, that day never came because it caught fire while parked in the driveway after a Sunday drive many years ago. The fire mechanically totaled it. I was so upset and angry, but I am sure that my grief was nothing compared to my uncle’s emotions. Fast forward to the present (or at least a few years ago). My son (much like his father) develops an interest in cars. I decided that I was serious about getting a collector car and something that I could wrench on and keep my mechanical engineering brain active (I have ascended to a management level professionally and I think my technical skill cells are in danger of being overwhelmed by management and bureaucracy!). Anyway, the first cars I was serious about buying I was a little late to the ball. There was a 280Z that someone had restored online for his son in the Midwest and was selling for ~$7500 if I recall correctly. I missed out on a bid on Bring A Trailer on a nice 260Z a few years ago because the kids were going crazy in the background when the bid ended. I saw a few Z’s locally here in Maryland, but those ended up being too rusted out or basket cases that were beyond my abilities to restore. So I widened my search to all cars I was interested in. I went and looked at a 2000 Corvette C5, but that was a case of never meet your heroes – as I was very bothered by the perceived cheapness and lack of durability of the interior and quality issues that seemed to be present with that car. I missed the ball on a ST-185 Celica Alltrac (always will love those), and got ghosted by another seller when I asked to see it and set up a Pre-Purchase Inspection. Then I came across my Z, which was somewhat local (within 100 miles) and I thought was worth a look. It passed all the tests and a mechanical inspection, and I couldn’t argue with the price, so I walked away the proud new owner of a 1976 Datsun 280Z. I name all of my cars after videogame characters, so I thought with the color and vintage, naming my Z after the main character of the classic video game Metroid, Samus Aran, was quite fitting: I think I am the 4th owner. As far as I can tell, I think she was very well loved by the previous owners, as the car came with a lot of records, a service manual, the original owners and maintenance documents, as well as even the original window sticker!

Greetings from Baltimore County, Maryland! I have been a long-time lurker and reader on this site, and I think I may have talked to a few members in person at car shows or chatted online. After searching for years, a few missed opportunities, lost bids on BAT, passing on a few project cars beyond my comfort zone, I finally found my Z in April 2023. As all cars that are 47 years old, she's far from perfect and will need some TLC that my son and I will eagerly perform and enjoy. I will start a project thread to document the work as it progresses. Looking forward to being an active member of this community! Paul