MY1PATH

You were right Captain Obvious it was not the change of washer effecting the carb vacuum. This is all I had time for today... Killed the engine at warm stable idol and again when it leaned out: found that both carbs were approximately half the normal level. So now I know for certain that I'm draining the bowls and that it's not just one carb. Despite the appearance of free flow when the pump is running and with compressed air (probably just not free enough) I am going to fish a line through the fuel rail and through the Hardline going under the car. If both those come out clean, this weekend I will pull the fuel tank and fish/inspect the pickup line. Edit: jar isn't level in picture so fuel looks lower than my line...

when It leans out letting off the throttle part way for a few seconds lets it recover. Uphill this means holding speed instead of accelerating at a lower rate. Hopefully I'll get to drive it this week and run a check after a hard pull.

No screens in my banjos. But a remote fuel source could help, thanks. I did expand my thinking to not just liquid fuel... Reading on pistion springs 1/3 the way down... https://zparts.com/index.php/resources/su-carburetors-explained/ When the carbs were on the L26 there was a THICK neoprene washer stretched over the base of the dashpot tube in the piston. I do recall it kept the piston from raising all the way up into the bore cutting off the top 0.25 inch or so... When I went to the L28 I replaced this with a thinner nylon washer that fit close but slid on freely. Two things are happening here, this piston is able to raise higher and the spring preload is a little bit lower. I imagine both could contribute to a drop in vacuum across the nozzle thus reducing fuel pulled into the engine. Or even not letting the piston drop fast enough to the lower engine speed after a shift. That's one more "new" thing I can look into when I get back to the car this week but I'm open to other ideas as well.

I have run out of ideas on this, car idles and cruises good, single gear WOT to redline 6k+ rpm is fine. Try to do it again and it cuts out. I have installed a wideband O2 to see what's going on and it's running lean but not right away. Here are some examples, all under WOT: 1st gear to 6k, AFR avg 12:1 -> 2nd gear starts cutting out at about 5k, AFR 18+:1 1st gear to 4.5k, AFR avg 12:1 -> 2st gear to 4.5k, AFR avg 12:1 -> 3rd gear cuts out almost instantly(3k?) 16~18+:1 Almost as if I'm sucking the carbs dry... Under half throttle my only issue is that it's not as fast ?. A balance between mid high throttle and earlier shifting can be found to get through the gears semi-quickly but it's not compromise want to keep making. Setup: L28 9.75:1 (flat top pistons + shaved P90 head, mild port work), L26 "C" cam, 1972? SU carbs, 3-2-1 header, 2.25 exhaust, 280zx "match box" ignition, no smog equipment. What else has been done (fuel system): Tank removed and cleaned, inlet outlet fittings fished with wire brush on string. Fuel hardlines blasted with compressed air from both ends (repeatedly, each time seemingly free of obstruction) YES fuel filters have been changed regularly, if not unnecessarily. Fuel hardlines around the valve cover were compressed air blasted before and after electrolysis cleaning and powdercoating. There are no filter screens in the banjo fittings on these carbs to be cleaned and the banjos and banjo bolts are free of obstruction as well as the passage to the float needle, the needle valve, spigot to the nozzle and nozzle itself. (checked AGAIN yesterday) Floats were set using view through clear hose method under pump pressure (I can check it again, has been a long time) Problem occurs with mech fuel pump, electric fuel pump and Mech+Electric combined. All 3 combos show 3.5-6 PSI going into the rail and pulling a hose shows plenty of flow. That's pretty much the fuel system. Please tell me if I'm missing something. I don't recall these issues on the L26 but have been one of those things I've been putting up with for a while on my L28. Any ideas? What's the limit on SU carbs? Have I gone past that? Contemplating higher lift cam, If I'm not over the limit will that put me over?

I had a great day at Z topia on Sunday. Put in 160+ miles with no lighting issues either way. The L28 cruises really well.

It all works great now! I was able to continue using the blue connector but the Green White (lights) and the Blue Red (wipers) next to it needed to be cut and run outside the connector since that corner melted beyond saving. I also took the time to cut out everything that is not in use going to those harnesses which cleaned up that area alot! Yep, had it for a few years now but failure was all very sudden. 200 miles on the new engine and one early morning it was all gone. All the lights were bright enough until the day it failed. I knew it was a mess, I was waiting to do a rewire to fix it all. I guess that was waiting too long. I imagine all the bad connectors were generating a small amount of intermittent draw all along but not enough to present a problem. I'm sure after some spirited driving with the new engine that 'duct' (or what's left of it) found its way into the mix and the the draw was enough to heat up the circuit slowly but not enough to blow the fuse.

Both happened. I found a bad connection, The BLUE connector near the fuse box was pretty melted and the Green Blue wire in that connector was making poor connection. It supplied power upstream under no load but dropped to 0v upstream when the switch was closed. The initial cause of this overheating appears to be a collection of things to include, too many exposed bullet connectors tucked under the carpet, some of them finding ground, one of which had found its way to another connector that is spliced with the hazzard light harness (hence the right arrow) AND get this, the wire frame from a disintegrated AC duct was making contact with the dash skeleton while one end had found its way into a free floating bullet connector which I think used to go to a glove box light... Getting it all cleaned up and put back together. Looks Like I just might make it in time for Z-topia this Sunday. DRL = Daytime Running Light.

Looks like exactly what happened. Been a busy few days so I haven't been online but I think I found it. I will post some pictures after I get everything cleaned up.

Unexpected, I have, kinda. When I supplied Green White with power from the headlight wire (heavy gauge almost no voltage drop) the Right arrow comes on this was before all the light fixtures were unplugged. I will have try the hot wire thing one early morning at everything is always very hot here in the desert.

Pulled every fuse out and tested it independent of the fuse holder. Then I checked each end of the fuse holder at the fuse clip and the joint at the back of the holder. With no lights or fixtures connected and switch in the off position Green blue wire (power to switch) shows battery voltage with some voltage drop as measured from the solder joint on the switch itself. So power is certainly getting there. When the switch is turned on (again no lights connected) Green Blue wire goes to 0v. So I guess it suddenly drops to zero when the switch is turned on, so I'm thinking like like what Steve said "too many parallel paths for current flow"? Dash lights and running lights used to be plenty bright before they failed. I would there was a time that they ran better than the headlights did... Until I removed the PO's botched attempt at DRL...

All lamp housings are unplugged (I've stated this in almost every one of my replies). I will get you pictures tomorrow.

-Ok replies are typed in inline with your quoted text. It was easier for me to compose it that way. And here are the pictures you requested. Thankyou, I don't mean to come off as ungrateful.

Good to know! So all the pins in that connector probed good end to end, they all click into each other and none of them are bridging. Definitely a short, with all the running lights and dash lights unplugged I'm still getting 5.7ohms resistance to ground on that circuit. I started my digging this afternoon at 3ohms resistance to ground. I found some funky stuff with a power antenna in back and another set of exposed but unused running light connectors inside the rear quarters... I started peeling back panels and carpet removing all kinds of unused electrical from seat belt sensors and seat pan sensors and a mess of Amp and speaker wires from a sound system that is no longer there... So I'm finding lots of little things and each time my resistance to ground increases but still not found the main culprit...

I'll have a closer look at the 9 pin again, maybe something bridged inside it... All signal lights and marker lights are unplugged right now. The resistance to ground went down with each one removed, I thought I might poke my way closer to the problem once all bulbs were removed from the circuit but with no luck...

yes, and I think it all worked for a short time after the swap too. I have a little melty on running light corner of that connector but my multimeter tells me its still making good contact. A full short will. A partial short or short to another device could cause excessive draw will stop all other items on the circuit from working. Fuse box appears to be in mint condition (front and back) unlike the rest of the car... what I'm trying to figure is where do dash/running, lights wiper and rt indicator arrow have in common... the rt arrow coming on when bridged power supplied to dash...

I've got a short somewhere... Ok actually found a few but not the actual problem... New motor is in with new matchbox dizzy and alternator. Old ignition box unplugged and alty wiring has been double and triple checked (and more). Car runs great and I'm excited to go places but I have a lighting issue that is keeping me off the road for obvious safety reasons. I first noticed it on my first early morning drive when I could not see the cluster. No dash lights and no running lights. I checked all the fuses and they are fine. So checked everything the car has: Headlights, brights blower fan, brake lights, Hazards, Turn signals all work. Wipers do not. I've read about a few various shorts in the running light fixtures so I removed all those and inspected one by one (left them off for now). The fixtures are good, one of the insulators on a connector was missing and there were some burn marks but not the problem. I found a few unused connectors like that in various places around the car and taped the off but still not the problem. I inspected and cleaned the column switch but no luck (yes, there is power coming to the switch). I did find that bridging power to the running lights from the headlights brings them on and lights up the RH arrow in the cluster... I am getting really burnt out on this!!! I just want the lights to work. Short of pulling up the dash and running through every shred of wire or doing a complete rewire of the car (it's coming, eventually) are there any suggestions you guys have? 1974 260z 2+2

I know this is an old thread but I thought I would add a finding... My '74 260z auto came with a D6F3-02 But the T-Bar had 14 stamped on it for 28 Degrees of mechanical advance. I think thats a new High and maybe a little scary. I am currently rebuilding an electronic D6K80-03 out of an '81 280zx (17 degrees advance) I'm guessing with fuel injection flame fronts moved faster and that's why less mechanical advance was used from '75-83

I know this is an old thread but I thought I would add a finding... My '74 260z auto came with a D6F3-02 But the T-Bar had 14 stamped on it for 28 Degrees of mechanical advance. I think thats a new High and maybe a little scary. I am currently rebuilding an electronic D6K80-03 out of an '81 280zx (17 degrees advance) I'm guessing with fuel injection flame fronts moved faster and that's why less mechanical advance was used from '75-83

Right, but that's an external site, its not within the forum.

I saw some classifieds in the 240k section but not here. My apologies if this is not allowed. Last week I picked up a parts car... Short block, heads and transmission are not for sale. T-tops and roof are not for sale. The body is straight with supposedly new bodykit and prepped for paint but the frame and floor are toast. Brand new Reproduction Dash plastic rest of the interior is hit and miss, cheap re-upholstery job... Too much else to list, Anything else just ask! Located in the mojave desert, ca. PM for contact information.

HI all I live in the Mojave Desert, CA. Earlier this month I picked up a '74 260z 2+2 ... Non-op, but I just got it running this weekend It had the stupid flat top carbs so I dropped in a set of 240z bell-top SU's and it fired right up. The rear brake piston on the 260z popped out and seized the shoes against the drum and we trashed the entire assembly getting it off so the car would roll onto the trailer. (seller did not have a good selection of tools) So I'll be disc swapping it since its already trashed on one side. And after that all I need is an air filter and it should drive. Last week I picked up an unsafe '81 280zx that runs and drives but the rear suspension links are about to punch through the floor and then some... I'm gonna use it for parts (2.8 block and 5 speed swap and AC upgrade if it fits?) and part the rest out. I been doing my homework on all the engine parts and I think I will wind up building the engine below for the short term before I build something bigger... 280zx block 260z heads (higher compression) 280zx cams marked "A" OR "F" ("A" same as 240 cams)(260 cams are degraded for emissions) 260z modified Intake with simple 240z balance pipe and Early SU Carbs. 240z roundtop carbs 260z came with headers I also own 2 OLD nissan pathfinders and a '79 yamaha xt500. Can you tell I like old Japanese vehicles? Anyway, that's my rides, my new Z and my current situation on trying to get this 260z on the road. Got Some pics from bringing it home.