W114

[Popeye]

Thank you Maki. There does not appear to be a connector, but I think I have enough wire length to unscrew the solenoid from the carburetor. Then I can take the base off and clean.

I noticed the rear solenoid is disconnected at what appears to be a fuse on the passenger fender (I’m still learning!); it looks like the wire pulled out of a connection. Perhaps that explains some of my idle issues.

[Maki]

I think that's just a connector rather than a fuse housing, iirc. at any rate, if it's disconnected I'd suspect it's giving you drivability problems such as surging at neutral throttle.

When I had my 250/8 I was able to salvage a couple solenoids from some used Zenith carbs. I fear they're going to be hard to find now. Many W114 owners replaced the Zeniths with Weber carbs, and I'd bet those solenoids had a lot to do with that. The Zeniths are actually pretty good carbs when they're working right. Replacement parts can be expensive, though.

[Popeye]

App appreciate the insight!

One more question for the experts: how do I install the bowl vent? See below picture; the brass bushing does not stay in place. I’ve tried (gently) tapping it with a hammer and drift to see if I can drive it home, but no luck. For now I put a few drops of Loctite blue to hold it in place, but this doesn’t seem quite right.

https://www.dropbox.com/scl/fi/p22pejezwq4jpqkge6in0/IMG_6867.HEIC?rlkey=q1zvnpp5kxhdq5lxxo5hvdcww&dl=0

[Popeye]

OK, so this is quickly turning into a carburetor discussion... what is the consensus here: Should I make a new thread?

Anyhow, my question is around the thick black plastic (phenolic?) gasket between the bottom and second-from-bottom layers of the Zenith INAT 35/40 carburetor:
(https://www.bing.com/images/search?view=detailV2&ccid=p2CSfClJ&id=C5FC8B89EC9D07C07CA4B71AC66193B704074F76&thid=OIP.p2CSfClJ0sI_QggquCqMzwHaNn&mediaurl=https%3a%2f%2fth.bing.com%2fth%2fid%2fR.a760927c2949d2c23f42082ab82a8ccf%3frik%3ddk8HBLeTYc Yatw%26riu%3dhttp%253a%252f%252fwww.franken-klassik.de%252fimages%252fstories%252fvirtuemart%252fproduct%252fvd013.jpg%26ehk%3dZ1vmKXKQXGJ5DnP7c hCaLatw8CEwBZo2G4l%252fSZ1gXps%253d%26risl%3d%26pid%3dImgRaw%26r%3d0&exph=1302&expw=708&q=zenith+inat+phenolic+gasket&simid=608031146329121038&FORM=IRPRST&ck=BF916646850E4F99E3A5FEB6A677C978&selectedIndex=8&itb=0&ajaxhist=0&ajaxserp=0, https://www.bing.com/images/search?view=detailV2&ccid=TCRTUYn%2b&id=F98B668D36ABE6657B2B8AA2B31935A97D6A486E&thid=OIP.TCRTUYn-TCScSZs4XVQyzwHaE7&mediaurl=https%3a%2f%2fwww.altopelhilfe.de%2fimages%2fproduct_images%2fpopup_images%2fCA-828438.JPG&cdnurl=https%3a%2f%2fth.bing.com%2fth%2fid%2fR.4c24535189fe4c249c499b385d5432cf%3frik%3dbkhqfak1GbOi ig%26pid%3dImgRaw%26r%3d0&exph=533&expw=800&q=zenith+inat+phenolic+gasket&simid=607988574642324631&FORM=IRPRST&ck=3F2638456BCE4C70A530112945C28669&selectedIndex=11&itb=0&ajaxhist=0&ajaxserp=0

The kit I purchased came with a black plastic replacement, similar to what I found in the carburetor upon dissassembly. However some internet sleuthing suggests this was originally a Bakelite(??) part, similar to the thicker spacers between carburetor and intake manifold.

Is the Bakelite better than phenolic? (Assume it should be used with thin gasket paper on either side.)

Secondly, it seems BMW still sells the part - but it has an additional O-ring. https://e9coupe.com/forum/threads/zenith-carburetor-bakelite-spacer-pictures-pn-reference-for-posterity.16271/

Any thoughts on if the o-ring makes for a better part?

Thanks everyone! This site has been an incredible resource. I have both carburetors disassembled, cleaned (ultrasonic), and re-assembled with fresh gaskets, viton o-rings, and membranes.

[cth350]

the spacer is an insulator to keep the hot manifold from warming the car too much. Either form of plastic is good. Classic Bakelite is an early plastic compound that can contain asbestos as a filler, so it's frowned upon in general these days.

As that BMW thread points out, be careful about replacement gaskets and these spacers, there are subtle differences in passageways between versions of the carbs. An Oring like that would definitely improve sealing characteristics of the spacer. I would hate to machine a recess like that into Bakelite. It should be easier to add to the phenolic one if you are a careful machinist.

-CTH

[Popeye]

Thanks CTH! I think I'll keep it as-is, using a new black plastic (phenolic??) spacer as I found it.

[Idle]

Originally Posted by Maki

The carbs on these cars have anti-dieseling solenoids that can fail. When they do they default into the closed position and cut off the flow of gas to (IIRC) the idle jet. That can impede drivability. The solenoids are NLA but I've known of people who fixed the orifice in the solenoid in the open position by various means.

I had one of these on a 1971 VW. The dealer could not keep them in stock as everyone they ever made went bad in a year or two. I think I finally just cut off the tip that sealed the passageway so the solonide no longer functioned.

This was before emissions testing so we were able to pull all sort of fixes that soon became illegal.

[Popeye]

Success!

I disassembled, cleaned, and re-assembled (with new gaskets, viton-orings, sealing washers) the carburetors. The rear solenoid wire had broken at the fender side - and the second was about to. I resoldered the wire to the terminal, and now have a solid "click" when connecting the solenoids.

But I still had a stall at idle once the engine warmed up (and the choke plates fully opened).

This weekend I replaced the fuel filter. Then I replaced as many rubber vacuum connectors (short pieces of rubber hose) as I could see associated with the carburetor: One on each carburetor, three at a fitting on the passenger fender side of the engine, and three (or two??) near the distributor.

Now the car idles without stalling and acceleration off the line is much improved (previously I had to pump the gas pedal twice to accelerate without killing the engine). Yay!

I have 15" of vacuum at a fully warmed-up idle, measured by disconnecting the vacuum hose at the brake booster. The carburetors seem to be reasonably synchronized, maybe 10-20% difference in flow when measured with a Synchrometer - so there may be some fine-tuning of the carburetors yet. (I have not made any adjustments to the carburetor, other than setting the choke plates during assembly - the previous mechanic has much better knowledge than me!)

Next up: I have a minor "surge" at constant throttle. If you pay attention it's present, but slight enough that I doubt a passenger would notice. I will continue to go through the vacuum lines and replace rubber bits. I have a mity-vac and may "deep-dive" the system if needed. (I also need to diagnose a leak in the central locking system - never a darth of projects!)

But, boy am I happy! Nothing is worse than a great car stuck in the garage when beautiful spring weather strikes!

A huge Thank You to all who have chimed in and helped educate me on the nuances!

[cth350]

bravo. -cth