Carb question...

Sean Haas

Sean Haas

Well-Known Member
Site Donor $
Messages
247
Reaction score
102
Location
Chicago
I finally got done with doing a semi-rebuild on my carbs - I replaced all the choke and secondary membranes which had tears, took off the top portion and removed and cleaned the jets on top and replaced one of the accelerator pump skirts and put new top gaskets on. I did not go all the way down to the float bowl as after that it appeared they were functioning but did blow everything out. choke/high idle seems to function OK. While trying to balance them I kept having issues with the back carb and upon looking found the top nozzle appears to be leaking and continues leaking after shutoff. I took a pic, you can see it appears to leak from the base but a video would show the drip from the nozzle as well. Advice on how to address appreciated. If it helps, I can hear air being drawn in as well when I open the throttle, I thought I had fixed this by fixing a sticking secondary. This carb has been giving me fits in general, after fixing a bunch of other issues hoping this is the last one.
1784406083907.png
 

Attachments

  • 1784406064488.png
    1784406064488.png
    440.3 KB · Views: 34
I’m not nearly the pro that some of the guys here are, but I’ve a few dozen carbs under my belt and feel like, if you don’t go 100% with a rebuild…(completely strip down, soak, clean, blow out, completely replace all perishable items and confirm clear passages) you’re just asking for trouble..at least in my limited experience..too many things to go wrong that love to hide from you..
We’ll hear from the big dogs here, soon..:-)
 
I should have said "accelerator pump nozzle" btw. But I hear you, I started to do that but the gasket between the jet and fuel bowl layer is really stuck on, plus I was hoping to avoid draining coolant and all that, but might have to bite the bullet. I wonder if the replacement accelerator pump skirt is causing this particular issue, I know they are not as thick as the originals. I've had the car 10 years and lord knows when the last time someone went through these.
 
Zeniths. I ended up figuring out how to separate the stuck jet stage from the float stage and took everything apart, inspected it and cleaned it, blew compressed air through everything and cleaned the float bowls although they weren’t bad. Have not had time to restart yet. Possible a couple check balls were sticking. Will post how it goes.
 
I disassembled everything, blew out all passages, checked the accelerator pump and reassembled. Still hear air and get lean backfire. I found something must have dislodged and plugged the accelerator pump. I took it apart again, blew air through both ways until that freed up and thought that was it, pump is working. But it didn't change much. I checked the fuel idle solenoid, both make the same ticking noise when reconnected. I am going to take it apart one more time and swap gaskets between stages in case there's a leak there but I'm running out of options to get this working. car will idle although a bit rough, I got the vacuum even between the two but on any acceleration I can hear air hissing in the back carb and I'll often get a backfire. Any tips appreciated before I throw in the towel. I did try spraying around come carb cleaner to check for leaks but didn't get any change.
 
Does it stumble and diesel? Be sure main butterfly is almost entirely closed. On mine rear butterfly was open too far and sticking on secondary linkage causing gas to be sucked down the throat.
 
No it does not. Based on another post you had I checked that previously and it appeared OK, but I will recheck. It's only when I accelerate it that you can hear the air hiss in, if I open the throttle slowly or hold it steady that's all you hear, but if I blip it I get the backfire. I should add the pollution control stuff is not on mine and the vacuum ports are plugged up, i should recheck those for leaks as well.
 
Long distance carburetor diagnosis is not my forte. That said, your description of a hissing sound sure sounds like a vacuum leak (or two). If you haven’t done so, consider reviewing this thread thoroughly depicting Zenith rebuilds. https://e9coupe.com/forum/threads/carb-question.50527/#post-445548 As suggested by that thread, is it possible you have the wrong accelerator pump part for your carb/s?

Bear in mind that no matter how pretty/clean your carbs may look, 50+ years of jostling and heat cycling can produce slight warpage that may not be fully resolvable with new gaskets. On occasion, other means may be necessary to ensure mating surfaces are reasonably compatible.


????

f71e858e-8156-40d6-bbcd-17f43a78b6fe-jpeg.122699


1625605123808-png.122462
iu

iu
iu
 
Thank you yeah diagnosing without being there is a crapshoot, I was just desperate for advice. I have gone through that thread, every published manual I could fine including the Jamie Kopp one and renewed all diaphragms. I will try a strip down, clean out, new gasket and have ordered the leather diaphragm for the accelerator pump to replace the thin synthetic ones that come in the kits. The pump itself should be fine as it's the one in there that worked for the better part of a decade. If all that doesn't do it it's off to a pro.
 
Hey Sean, reading with interest. Been there with my pair of Weber 32/36s. Didn't know a lot when I first started to improve their operation, but at the end of the journey, I fully understand and can appreciate the tuning to get the car to run well. I know it is your Zeniths that are the immediate problem, but in my case, I was not completely satisfied until I was certain I had the valves set to spec, ignition, timing ...same, and finally, carbs serviced and tuned to Weber instructions. All came into focus and my E9 runs great. This is a very rewarding exercise, though it takes the time it takes, but you will solve this and have many, many miles of reliability to enjoy. Good luck! Mike
 
Valves, timing, etc. were checked last year and should be good. I won't get to it until the weekend but I'll either figure it out or off to the pros after that.
 
Make sure that your gaskets match up exactly, there have been some that interfere with the float The separate sections do tend to warp slightly and all surfaces should be sanded down on a flat hard surface with at least 320 paper wet In the lower section, on the base gasket, there is an o ring,make sure that it is there and protrudes slightly above the gasket, this is where a lot of the vacuum comes from for the internal passage ways for the carb

There is also a jet that often gets misplaced on the secondary side under the air corrector jet , carb will run poorly id this is missing

Thanks, Rick
 
Good advice, the float part I did check for free motion but have not re-started after installing the new gasket. I recall seeing a pic of that o-ring somewhere so will make sure it's there. I only took the jets out to clean and replace one at a time so hopefully I did not miss anything.
 
OK, don't want to speak too soon but I may have solved it. Earlier in the week I took the top two layers back off (that's all I've ever taken off, I did not want to disturb more than I needed to.) I blew everything out again and replaced the gasket over the float bowl secntion - why did I not do that the first time? Because the nice old guy on youtube who does this on mercedes said you can usually reuse them, and mine was really stuck on there. So I took 45 minutes to carefully scrape that off, I could see a lot of moisture where fuel was getting drawn where it shouldn't. I started it tonite and seems to be much better - no big air suck and the carbs sound the same, no backfire on quick blips. I only had a few minutes to check it out and do a quick balance so I'll try to tune it tomorrow and see how it goes. Cross fingers.
 
You must log in or register to reply here.
Back
Top