RJK

Hi folks-so to give some background, I've read up and watched videos of people tuning 2x SU carbs on a 240z, and had my first attempt at it today. Have a bit of confusion, and would love some tips. Background: -'72 240z, stock SU carbs(to my knowledge?). Were rebuilt about 2-3 years ago and balanced at the time. Fuel pressure regulator in line pre-carbs. Cannot verify actual PSI, have not tested with gauge yet. -Over the last two years, the car has run progressively worse. Last summer a changed out the spark plugs, and it temporarily helped. Recently I pulled all the plugs, and 1-3 looked clean, but 4-6 all were black at the tips. I am assuming the "bumper side" carb is running richer. Last month or so, the car would have an extremely lumpy idle. If I got on the throttle at all while starting, it would flood out and I'd have to wait to get it to start. Only starts with ZERO throttle, zero choke, and then I have to start it 5 times and massage it and give it flowers. As I have read it, the mixture is controlled by a "nut" on the bottom of each carb. See photos; I can't feel a "nut", but there is a "dial" that I can turn by hand. I'm touching it in the _6813 photo. I got the car to idle today, and put an airflow meter on it. firewall side carb read 10, bumper side read 16. Turning this dial on the bumper side carb had no effect on the idle speed, or the airflow. by adjusting what I understand to be the idle screw( touching this in _6812), i got the airflow meter down to 10, so they were pretty close. the car held an idle, and seemed to run smoother, but I still don't think I'm adjusting the mixture, and if I am, it is probably completely out of whack, as I probably ended up turning that "dial" a solid half turn (counterclockwise from top). while the throttle is responding closer to normal, as you can see in the video, I was still able to get it to stall out from a quick burst of throttle(which I have been constantly on guard from when driving the car). Also, what I assume is a water vapor or fuel overflow tube dribbled a bit of liquid from the firewall side carb(again, see video). Would love some pointers here. Thanks a bunch folks! IMG_6811.MOV

I have never given my fuel pump a close inspection, as it was on the car when I acquired it, and it never failed. I am now wondering if it may be over-spec'ed for the use. What is the best fuel pump to be running, in you folks' opinion? Should I go mechanical, or stay electrical? the cutoff switch is nice, however I have struggled with some rich running in the past, and won't be surprised if the PSI is higher than needed for 2x original SU carbs. Curious what is suggested, with an eye towards electrical since the wiring is already there. (I run mechanical on my '76 2002, and while it takes more cranking to start if it's sat for a week, it's not a problem for me ultimately). @SteveJ that last pic is, for all intents and purposes, the ammeter reading with battery topped off and car running. the car came off a trickle charger yesterday, and read 12.8V before I started it today. I'll throw a DVM on it soon and get an actual number. And yes, the delta between the needle in that pic and the center line is the fuel pump draw; when i killed the fuel pump at the fuse, it was almost dead on center while running.

Well I think I have good news. I pulled the fuse for the red wire at the starter, and it's the fuel pump. I was able to briefly run the car without, and the ammeter definitely hovered much closer to the midpoint. the previous owner installed a fuel pump that is quite loud; I don't know if I've ever heard one this loud. There's an aftermarket cutoff switch in the car, which is actually nice from a safety POV. I re-installed the fuse and ran the car til everything was hot and "run in". Attached is where the ammeter needle stayed stable.This seems better, no?

@SteveJ a million thank yous!!! extremely helpful tips here, kudos for all your info. I had the ground of the DVM alligator clipped to the battery ground terminal, and the positive lodged inside the molex connector(red wire) that leads from the alternator. battery was fully topped off from a trickle charge before i made this video. will pull the fuse on red wire tomorrow, test, and see where ammeter lands. battery is 2021, and i am pretty strict about keeping my old cars on trickle chargers.

Thanks Steve! So the car passed your test, and did as hoped at the green and red wire of the alternator connection. I don't know if this was an issue before, or one i implemented BY testing, but the blade of the cars wiring harness was popped out of the connector, so initially the test failed. After diagnosing, I found the blade to be just out enough to not conduct. Pushed in, re-tested, works as hoped. Please see video of both DVM at the red alternator wire as connected, and the dash ammeter. This is with the new "pure energy" starter installed. It's definitely not pegging now. This is just a cursory "in the shop" 30 second test, I havent put the car through any paces, but does this look normal-ish to you all? IMG_6742.MOV

Thanks Steve! I'll pull the connector on the alternator and throw a DVM on the red wire to its termination point, and see if I can't verify that crimp. yes, the wire between the solenoid and starter, that looks charred, is actually burned through the insulation in one spot. Rock Auto lists this; I do not know Wai Global" as a manufacturer.. https://www.rockauto.com/en/catalog/nissan,1978,280z,2.8l+l6,1209260,electrical,starter+motor,4152

Ok, more info. -the red wire from the starter is fused, and leads to a relay at the firewall. didn't trace further yet, can do if relevant. see pics. -the starter solenoid wire is fully burned through in one spot. -I am really going off memory, but I believe the 6 pin plastic cap at the voltage regulator location was bought from one of the more prominent Z car retailers, specifically for use with an internally regulated alternator. -the starter gear spins freely, and the teeth show no wear. -I recently bought a big battery charger that has an alternator test mode of some sort; maybe I should test the alternator to verify it's efficacy?

Yea, that charring of the insulation definitely concerned me, hence the nature of my post. This may be a daft question to ask, but what happens if I connect a voltage regulator to an internally regulated alternator? Does it just function as a redundancy? Also, is there a "known quantity" starter and alternator available on the market? I vaguely recall there being talk of rebuilding a 280z alternator with modifications, but I found it confusing... @SteveJ what is a Frontier alternator? I am googling and not finding it, if it's a brand name. Also, you said "13.2V at 2k RPM is not good"-safe to assume I should be seeing HIGHER than that, correct? My 928 probably runs 13.8 or so at ~2k. THANKS for all the help folks! I don't know if a poorly regulated alternator could result in the starter failing, but it does appear to be that this starter has crapped the bed after a very short lifespan. I generally assume "user error" on my part, but maybe the part itself has failed. Nevertheless, no driving til I figure this out.

Thanks. At the time I replaced the alternator(maybe it was earlier than last fall? Post-Covid all time calculation is a bit of a blur for me), I recall being advised to use a jumper in place of a voltage regulator, which is in the car now. Maybe this is the source of the problem? I just ordered a voltage regulator and a new starter motor from Z Car Depot. I will investigate the termination point of the red wire at the starter motor as well. Thanks folks!

The red wire to the starter: I have no idea, as it was implemented by a previous owner to me, or original to the car. I do recall that much. Got to the car today. At rest, battery shows 12.8V. I only ran it briefly as it was in the shop, but at idle, this jumped to 13.0V, and around 13.1 or 13.2 at ~2k RPM. The first time I tried to start it, the starter failed. It momentarily spun, and then just stopped. 2nd time I tried to crank it, the starter spun and it started.

Thanks ya'll. So, if memory serves, last fall the car was behaving like it was starved for voltage when starting, and the battery was pretty old, and I did the old "while I'm in there" with the alternator and starter, cause I wanted the car to be reliable and have two less things to fail. Possibly dumb in hindsight, but if you think that's dumb, boy have I got stories for ya. I recall struggling with the new alternator at one point, and going around about internal regulation, as well as the in-line fuse piece for the starter. I will take a battery reading with the car at 2k RPM, and how it behaves relative to throttle, and report back. Thanks.

Hi folks-so I had a pretty strange day yesterday in my 1972 240z. Some specs: -2021 battery, never ran down -new alternator -new starter, with new inline "fuse" I installed the new starter and alternator around last fall. Since then, the battery meter in the dash would periodically peg all the way to the right, but only occasionally. Most of the time, it would hover near the middle marking, maybe swing upwards by a small bit when running. I had the car out for 2x 20 minute drives yesterday, and by the second drive, the meter was pegging all the way to the right. I had to gingerly ride the throttle to keep RPM's near 2k to get home, as the car has been wanting to stall out with a hot engine+low idle+fast throttle application(another issue for another day, the 4/5/6 carb is running too rich). Near home, I gave it a test, and let off the throttle. Sure enough, it held idle with no throttle but the instant I gave it throttle, it stalled. Here's where the issue starts: 10 seconds later, the starter wouldnt even spin. I let it rest for 30 seconds, and the starter luckily spun enough to start, and I got home. Also, the sound of the starter is different now. Please see pics of the insulation on the wire; I can't tell if that looks correct or not. Also, I got a mild burning smell near the starter when I sniffed around the engine bay after driving. I checked the battery when I got home, 12.8V, so I don't think I've got a bad battery. Any ideas as to what is going on? thanks for the help!

Havent had this experience in a long time, but I'm sure it happens to the best of us.... my specs: 1972 240z. MSD ignition system installed recently, original distributor. New plugs last year, new wires. For the last few months, I've had periodic issues at low RPM(stopped at lights) with the car stalling; once I'm over 1500 RPM, engine has run smoothly. Stalled at a light, and would not start. Took the air filter cover off, blew it out, and it still didnt start. Eventually had it towed back to my garage (today). I never have had to address the fuel pump, as I've never had problems with it. Fuel pump very audibly runs, and I smell fuel when goosing the throttle when trying to start it today. I know until I throw a fuel gauge on it, and a spark tester, I am basically guessing as to the culprit, but in the interest of upgrading the car, should I consider a new distributor? If so, what's the most reliable unit that will play nicely with an MSD system? Oh, one more data point....Over the last 2 months or so, the battery gauge at the dash would periodically swing up to the far right, and twitch around. It would do this for 5-10 seconds, and then return to a 12-13V ish location on the gauge. Thanks for any thoughts!

Hi folks-I got my Z out this morning for a drive, and had a strange experience. car started the drive exactly as expected, with gauge readings exactly as expected. about 15 minutes in, I turned the fan on. almost immediately, my alternator gauge jumped from middle-ish to peg all the way to the right. car started to stumble, and stalled out. i had to keep my revs in the 2k range to get to my location without stalling out more. turning the fan off, it crept back towards middle point, SLOWLY. got to my destination. 2 hours later, i left(no fan on this time). alternator gauge looked normal-ish at first, but then started to get jittery, and be in the 13-14V range. had some more stall outs at lights, and had to ride the throttle when stopped. my specs: 1972 240Z. new battery, new alternator, MSD ignition upgrade. 5 new plugs last year(I found that one had been helicoil-ed at one point, and couldn't find the right sleeve), one old plug. this wasnt a problem before. any thoughts as to what is happening here? thanks!

The 6-8 ounces I referred to was from the FILL plug. Not the DRAIN plug. When I opened the drain plug, in total, somewhere near 1.5-2 quarts is what the diff held. Every time I've changed diff oil, the method of filling I have read in every WSM I've seen was to fill at the fill plug til it starts to drip from it, seal it up. The previous owner of my car must have tilted the car before filling. I was asking if this was standard operation procedure on Z cars for some reason, or if this was an isolated event. Sorry, I didnt check the actual diff casting, but it's a 1972 240z, surely stock diff from my visual inspection.