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Building A L28 (Na)

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So I think my borrowed Carbs might have taken a dump on me. Either that or it's the fuel pump, but I haven't had the time to check the pressure yet. I do know that the carbs have been running like crap due to the bad accelerator pumps. 

Engine cranks, but won't come on. I took the top lids off each carb and noticed they were covered in "cheese," as I like to call it. Not the sharpest blades in the Weber arsenal these lads, I'm sure.

At first I thought the carbs might have been flooded, so I cranked the engine for about 10sec with WOT to empty them out and then tried starting it again, but to no prevail. Tried some carb cleaner, but that didn't do much. At one point, I did get a little 

How much fuel is there suppose to be in the bowls? The floats are all properly set.

It had been raining pretty hard, so maybe the wet/moisture wasn't complimenting my dizzy or the carbs. I'll check it again once the weather dries up.

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  • 2 months later...
On July 7, 2016 at 8:23 AM, EuroDat said:

Nice sound. You need a set of bumpers/brackets:D



I'm replacing the big 5mph bumpers with the slimmer ones. Had the whole thing off when I was dropping the g-tank for cleaning :)

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On July 20, 2016 at 0:17 PM, siteunseen said:

Are going with the cable throttle pull later on?  

Are you talking about the throttle return spring I have? That was only temporary - it's not there anymore :)

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On July 22, 2016 at 3:38 PM, Zed Head said:

Actually, in the picture, the stock linkage does look a bit contorted, from the firewall to the carbs.  Does it move freely like that?

Moves just fine. Haven't had any issues with it.

I got the carbs air synced (5kg/h), the floats set, the linkage synced and all the right jets (in theory) - now I need to adjust the idle mixture and accelerator pumps, if needed.

Zedyone recommended an AFR kit that I recently got to help with mixture tuning, but I'm having some trouble with electronics at the moment.

My voltage drops (dives) and shorts all accessories the moment I use any accessories, including head lights. Fan, headlights, windshield wipers, etc. All of these short out all the electrics. The only thing that doesn't are the turn signals and my electronic fuel pump that's hooked up to the starter. One of my brake lights also caused the short (volt drop every time I braked) but I disconnected it and now that doesn't happen, but the previous issue remains. 

Since I air synced the carbs, they've began to stutter and hesitate upon acceleration, so I definitely need to figure that out, but I would like to solve the electrical side of things, too.

Got a lot on my hands right now! :)

Edited by TheCrazySwede
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  • 1 month later...

So been doing some more tinkering.


To try and attempt diagnosing my electrical issues, I've reverted most of the electrics to stock:


  • New Externally regulated alternator
  • New voltage regulator
  • New battery cables (x2)
  • New OEM Fusible links

With key set to "ON" -

  • Alternator reads 12.20v
  • Fusible Links read 12.20v
  • Battery reads 12.23v

As soon as I turn on my headlights, the volt gauge in the car drops to 0. Running lights, parking lights and dome light won't come on. Same effect occurs if I try to turn on the fan, use wipers or hazard lights. Headlights come on and turn signals work. One of the brake lights also causes the "short" issue, but with that particular light disconnected the issue no longer occurs. Swapping bulbs with one that does work still causes same issue in that particular light.


  • Alternator reads 12.20v
  • Fusible Links read 12.20v
  • Battery reads 12.23v

I checked the ground wire from negative battery - good. I checked my fusebox - good. When I first made the swap, the alternator was pushing out 17v before I swapped it. It may have fried something along the way, but I don't know what. At this point, is there anywhere in particular I should be looking?

Edited by TheCrazySwede
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  • 8 months later...

Quick update:

Bought a new harness and I'm going to strip the car down and re-do all the wiring. Figure I'm going to want to do that anyway. Hoping I find something along the way.

Here's the sound of the car with the carbs better tuned (Getting a hang of it!)



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Are those 45mm's or 47mm's I have a set of 47 in the closet yet to be installed. Let me know what you think of them.


Edited by esmit208
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On Tuesday, May 09, 2017 at 1:12 AM, TheCrazySwede said:

Awesome! Did you paint those yourself? I have 45's

Yes but it just my own personalization.

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So the Z no longer has electrical issues!

I ended up ditching my current harness and re-modified a harness out of a 73 240z and used that. Works great and no longer giving me issues! Also installed some led bulbs in the car and some HID's while I was at it.

I' currently facing an odd issue...

During idle, Cyl4 and 5 don't fire. I checked for spark and compression - both give positive results. Turning the idle mixture screws don't do anything, either. Something get stuck, possibly? Under load I believe the engine runs on all six, but definitely not under idle (disconnected Cyl4 and 5 serves no changes to the idle.)

Anyone have any tips as to why? The only thing I can think of is maybe the needles getting something stuff in there...

I tried spraying starter fluid into those carbs and didn't get any change in idle behavior - but I do get that from any other carbs.

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  • 3 months later...

Ok, it's been a while since I gave an update, so here it goes!

Every wire in the car, from front to back, has been redone, replaced or discarded. The car runs on what is needed. No heater, no fan controls, no radio, no antenna switch - not even the fuel light was spared. The car runs on only what's needed, nothing more and nothing less. 



The issue with the idle and pilot jets is resolved, too. Idles and runs on all six cylinders now! I'm not sure what did it, but I replaced my filter, cleaned my tank, cleaned out the carbs as best as I could and messed around with the idle mixture - and eventually it worked!


I've spent many hours now diving into every piece of literature I can find on DCOE carburetors and I've surely learned a lot to the point where I feel very comfortable working on these guys. What I couldn't find much on was what parts of the DCOE family (Weber, Mikuni, OER, Solex, etc.) is interchangeable - specifically talking about jets.

What I learned is that Weber idle jets work as long as you get the appropriate seats for them. Mikuni Air Correctors work on these carburetors, too, and fit right into the emulsion tube. The mains, however, only seem to fit with OER ones. I went through a lot of different setups to find something that works for this engine and so far the perfect recipe seems to be:

Mains: 135

Air: 160

Idle: 65(OER)/65F9(Weber)

I am currently running 62.5 pilots, but it's a tad bit too lean when cruising. i've tried 70F8's and 70F9's and they're both too rich. My guess is that 65's should fit in perfectly, but they're still on their way from Japan since I'm going with the OER one. The F9 designation on Webers is the same as the OER.



I also got a wideband hooked up now so I can get proper readings on this thing. At idle I'm currently sitting at 12.7-13 AFR, it goes up to 14 when cruising under 2kRPM (should richen up a bit with the 65's) and I get in the mid 12's at WOT, which seems to be the sweetspot for this engine.


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