Project Theseus

[Noll]

Hey Noll.... amazing work, as always. You have to be happy with your progress..... it's looking like a car. I know finding fusible links might be difficult. I replaced my fusible links including with a fuse box designed for a stereo system but have plans to go back to factory fusible link box. (76 280Z). I soldered up some push on connectors back to back to plug onto the female connectors in the fusible link box and to accept a modern ATO (think that's what they are called) fuse. Picture shows my connectors with a 60 amp fuse. I haven't made the change yet (too many house repairs!) but I'm pretty sure I did a test fit way back when and they fit quite nicely inside the factory fuse link box!

Many thanks! Getting close to first startup which is exciting, the car hasn't even had a battery in it during my ownership until now.

That's a good idea and something I was thinking about. That looks like it will fit in perfectly; if I can't find links or the right type of wire to make my own I'll definitely go that route. It seems like nissan might still have them for cheap, and if not I'll see if my local Napa might have fusible link wire. If not, fuses it is.


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Had another go at the short issue after a good night's sleep, and got it sorted out. Unplugged the remaining fusible link (so the rest of the car's wiring wasn't a factor), and started checking every part of everything - starting at the starter, working through the larger fusible link connection, to the shunt, onwards to the other fusible link connection etc.

Found the culprit after eliminating everything else as an issue - the terminal on the alternator that charges the battery is a direct short to ground, zero ohms to the chassis. Might be able to pull it all apart and fix/replace the insulator that's likely the issue, but for 60CAD/45USD (plus core charge, but I obviously have a core) it seems a no-brainer to get a reman alt and not deal with the unknowns (plus this car sat outside for a very long time before I got it and I have no idea how old the alt is anyway).

Right-side terminal in this pic:





And snapped another pic of the car while I was climbing up to get some parts out of storage.




At this point the remaining electrical work should just be the alternator/fusible link, finish making the headlight relay harness, and connect up all the switches in the center console (and the console itself). The latter two don't really need to happen for the car to be able to start up though, will do them later.

So, alt/link, make sure there are no further electrical issues, make exhaust, put some gas in the tank, and go for first start!

[zedfoot]

How does the shunt work? I assume it prevents all the current having to go through the dash. After having the cabin fill with smoke on the DVP, I switched to a voltmeter and kept the heavy current out of the cabin.

[Noll]

How does the shunt work? I assume it prevents all the current having to go through the dash. After having the cabin fill with smoke on the DVP, I switched to a voltmeter and kept the heavy current out of the cabin.

From the research I've done, it seems like it's a piece of metal of a calibrated size/length (and thus resistance) that joins the circuit directly from the battery to the one that powers everything else. 2 smaller wires (left in the picture below) go to the ammeter; it works by seeing the draw in some way between the two main circuits (this is where the length/resistance thing comes in, not sure of the specifics).

As you say, in the 240zs it was in/under the dash and less beefy than the 260/280 one, in my case it bolts right below the alternator voltage regulator in the engine bay.




I also plan to go to a voltmeter eventually, and will have to if/when I go to an internally regulated alternator as it stops the ammeter working in some way (can't remember offhand but was in one of the many threads I looked at while researching it).

If the shunt blows up the entire car goes dead, as it acts as the join point that the red circuit in my pic is powered from, and that in turn powers most everything in the car. Easy to splice/join the two big wires if so though, obviously the ammeter stops working if that's done though.

[Danielz]

Noll - you are absolutely correct in the description of a shunt. We use them all the time in industrial DC applications to measure the current in a circuit. You can google dc shunt for description of how they work. Ammeters were common in a lot of automobiles way back when but gave way to voltmeters - probably because a shunt failure left the car dead and voltmeters are cheaper than an ammeter (no shunt)and wiring costs were less. And I suspect shunt failures may have lead to more than 1 auto fire. For my money, I would convert to a voltmeter now while you are in the wiring phase. Datsun converted somewhere between your vintage Z and the 280. Mine has a voltmeter.

[Danielz]

I've been doing a bit more research on fusible links. Some sources say they are the same as a fuse; others say you should not replace a fusible link with a fuse. A bit confusing. Both are designed to protect the wiring. You can purchase fuse link wire (saw some available in 4' lengths) from Amazon, Autozone etc and you could make your own links. I'm not sure if Nissan's colours used in the Z is the same as present day offerings but as long as you match current ratings (ie. Datsun brown link is 80amps) all should be fine. I might reconsider using my ATO fuse solution.

[Noll]

I've been doing a bit more research on fusible links. Some sources say they are the same as a fuse; others say you should not replace a fusible link with a fuse. A bit confusing. Both are designed to protect the wiring. You can purchase fuse link wire (saw some available in 4' lengths) from Amazon, Autozone etc and you could make your own links. I'm not sure if Nissan's colours used in the Z is the same as present day offerings but as long as you match current ratings (ie. Datsun brown link is 80amps) all should be fine. I might reconsider using my ATO fuse solution.

Glad to hear about the shunt stuff - electrical isn't my specialty but I try to muddle my way through and figure stuff out. I plan to go to a voltmeter at some point, but the ammeter seems to work fine (see post below), and sourcing one will take time. The sort of thing to do one weekend afternoon after the car's on the road, doesn't have to happen this second.

As far as the link/fuse thing goes, there does seem to be a bunch of conflicting info. Some searching says the black wire that I burnt is 80A equivalent, same as the brown. I'm currently weaiting to hear back from my local Napa about getting some wire to make my own, and have emailed the local nissan dealership to see if I can get them new. If not, fuses it is, I just lose the "slow blow" functionality that way which won't harm anything in the harness if there was to be a short etc.


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Got a 50a fuse from Napa to get the wiring back up and running while waiting on a new fusible link (if I can find one that is).




Next order of business, get the center console in so I could plug in the hazard switch as a lot of stuff runs through it. Seems i have a 240z center console, had to modify the front mount for the dash to sit in the right spot to bolt up:




Will need to trim the bottom of the heater control surround slightly, which is why it's slightly awry here. Interior is coming together nicely though!




The result - pretty much everything seems to work! horn, turn signals, hazards, blower motor, wiper motor, washer motor, etc etc.

The things that currently don't are all dash backlights, the map light, and the starter won't kick on. I initially thought there was an issue with the electric fuel pump too, but some looking at the wiring diagram shows it only ever kicks on when there's enough voltage from the alternator - safety cutoff for accidents etc. I'll run it direct to a battery for priming before first start then reconnect properly.

Oh, and the right-side turn signal indicator bulb is not working (turn signal itself is fine); will pull the gauge and replace it eventually I guess.








Spent a bunch more time pouring over the wiring diagram, and got the interlock wiring all sorted out. my car is missing the emergency switch and interlock relay, but i can bypass whatever's left by just connecting two wires in the emergency switch plug.

[url=https://flic.kr/p/2miZTfp]

Will do some troubleshooting on the backlight issue, but that's also not needed to get the car running initially. Exhaust needs to happen next then make sure all the vacuum lines are hooked up and try to fire.

[Danielz]

HI Noll.... on my 76 280Z the fuel pump is controlled by a relay. When you turn the ignition switch to the "on" position, the fuel pump starts running (you can hear it) then once the car starts running the air flow meter (AFM) opens up and keeps the relay energized. In this way, if the car stalls (or stops running due to accident), the fuel pump shuts off (no air flow to keep it running). Not sure if this is how the 74 260 is configured (if I can find the wiring diagram you are showing, I'll take a look). I know there has been other posts about using a Ford style inertia switch.

[Danielz]

HI. found the wiring diagram! Your 260Z has two fuel pump control relays - one off the alternator and one off the starter. I suspect (have not followed the wiring yet) that the one labeled "starter" energizes when you turn the ignition to "start" and fuel starts to flow (disconnect battery lead at the starter so the starter solenoid energizes but motor doesn't crank and see if you can hear the fuel pump running). Once the engine is running, the one labeled "alternator" energizes when alternator makes voltage and maintains fuel flow. As long as the alternator is turning and making voltage, the "alternator" relay remains energized (once you let go of the ignition key, the "starter" relay de-energizes). Pretty sure you have already figured this out but just in case..... Keep up the exceptional work. (my background is electronics / industrial drive systems... so if you need electrical help.... just post.. I look every morning).

[Danielz]

Back again... studied the wiring diagram. The contacts for both starter and alternator fuel cut off relays are wired in series... therefore, both relays have to be energized to allow fuel flow. And not as I previously described.... So I guess, being a carbureted engine, it relies on residual fuel in the carburetors to start the engine. You might have to manual put gas in the carbs to get it to start the first time or prime as you previously described

[zedfoot]

Put the air hose to the return line to push gas through the system.

[Noll]

Danielz - thanks for taking a look at the diagrams, much appreciated. I try to muddle my way through but always good to have someone with a background in electrical take a look! As you say, there's 2 relays in the 260, from what I've read the 2nd turns the pump OFF when cranking (the mechanical pump is obviously still getting fuel to the carbs in that situation, but not sure why specifically they did that especially as it should be off anyway due to the lack of alternator voltage). Someone's already put a jumper on the plug for the 2nd one to bypass it completely (possibly due to interlock stuff?) - the alternator cutoff should be perfectly fine alone and a good safety measure to keep. Will need to look into an inertia switch or similar whenever I eventually go to an internally-regulated alt I suppose.

For now I'll probably just run the pump direct off the battery to do the initial prime as it's all wired up anyway and will be good to make sure the pump does work. The air line trick does sound like a good one Eric, not sure if it would work for my car though with how the evap stuff has been deleted; would likely just vent the pressure out instead of forcing fuel through the lines.


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Got the gauges working - dome light fuse replaced and voila. Always nice when it's simple.




Got the car to crank over with the key too now with the interlock bypassed. Took a little while but the oil eventually got up to the head after the oil pump caught prime, so all is well. Great spark too, so just need to prime the fuel system.

Took the header off and welded on a v-band flange, then put it back on the car and properly bolted it and the intake up fully. Got the vacuum lines sorted too, damper oil in the carbs, and hooked up the throttle linkage, so that side of things should be good to go.






Got a bit carried away here and ended up building the entire exhaust. I am exhausted (no pun intended), but hey, it's done! Pretty happy with it for my first go at making an exhaust and what I had to work with, it hugs the transmission tunnel and underside pretty well considering. Re-used the old resonator as it was still in good shape and no point spending more money for no reason.




Will get it back on the car tomorrow probably, then just need to do fuel prime and I can get it started (hopefully).

[Noll]

Figured I've put enough stuff together to throw the front strut bar on. It looks great on the car but doesn't quite fit for some reason.






Also realizing that the bar section that extends out about as far as the strut nut will probably be a hood clearance issue, I can cut the top half off and plate it without much hassle though.



And the culprit, it hits the valve cover for some reason. I really don't know why given that the strut tops are higher than stock (thanks to the camber plates) and it previously attached to the 3 strut holes, but oh well. It's an issue and I'll fix it.






The solution is probably just going to be to chop the bottom half out of the two cross-tubes like this then plate over it with stick-gauge steel to maintain strength. Won't be hard to do and I still have some of the paint I used left over to touch-up with.

[Noll]

got the Z fired up (mostly) for the first time! It stumbled for a bit (it sat for probably 20 years, so fair enough), idled nicely for a few more seconds, and then backfired out the rear carb (as far as I can tell from the video anyway) and for unknown reasons revved to the moon before I shut it off.

Not sure of exactly why (throttle linkage didn't seem to be stuck from what I can see in the video, no vacuum leaks that I can think of, etc), but will figure it out then fire it back up after priming the fuel system properly - was just running of what I put in the float bowls there.

if anyone has any suggestions as to what could have caused the runaway I'm all ears - I'd say the backfire pushed the throttle blade open but the linkage wasn't stuck so I don't see how that would have caused anything more the a blip in the throttle.

EDIT: pretty sure it must have just been it running out of gas in the bowls and going way lean, you can hear it starting to creep up just before the backfire and big rev. Throttle linkage is smooth as silk so can't be that.

[Noll]

Was planning on doing a bunch of stuff today, but ended up spending hours dealing with the fuel system as every single compression fitting was leaking to some degree for unknown reasons. Fun times. Got it sorted now, but that ate most of the day.

With that done, made a coolant overflow bottle/mount. It's a bit extra, but a fun touch IMO and cost me nothing. Will be refining the bracket/cleaning it up then painting and adding foam padding.

[Noll]

Got the Z back on the ground today. Sitting rather low, I like the look but will need to do some testing to make sure it won't hit on anything (tires to fender lips up front under hard compression is probably the most likely culprit).






Clearance: exactly one sideways 2x4.




Turns out I miscalculated with the exhaust when building it on wednesday - in my defense I was very tired and it was dark lol. Will do some chopping (likely near red lines), and get it raised up properly. Flex pipe gives me wiggle room with the front section.




Did a bunch more misc. work today too - coolant added (will need to add more as it runs and pushes the air out of course), lower seatbelt stuff bolted in, seats bolted up properly, defrost ducts plumbed, wiring cleaned up under dash, and put down some 3M grip tape where my feet will go. Would have been better if it was black, but it will be functional - without carpet the floor would probably get pretty slick when wet.

Other than finding the glovebox (put it somewhere for storage and can't remember where), interior stuff should be good to go from the backs of the seats forward.




I then went to start on the headlight relay harness and promptly dropped and shattered one of my nice Bosch H4s (not from high up either, just bad luck). ****. Thankfully i still had one of the lights that was on the car when I got it (housing rusted to nothing), so I removed the broken lens, and replaced with the one from that housing. Waiting for the sealant/glue to dry at the moment. Won't look exactly the same as the other one of course, but will work as it should and you'd have to look at both pretty closely to tell I hope.