Zenniths, replace or repair? - PeachParts Mercedes-Benz Forum

peebeeNZ · #1 10-03-2002, 06:32 PM

I need to do something with my "Zeniths". They need totally rebuilding. I can get a used pair for about $100 less than getting mine rekitted by a professional or buy the kits myself and have a go. There is no warranty on the used ones but I can hear them in the car. I would like to know through others experiences what people reccomend.
Thanks for any coments.

gmask · #2 10-04-2002, 02:31 PM

Hey,

They are a lot of posts here about Zeniths so you may wish to search the forum for Zenith and od some reading.

You may need to both buy a set of zeniths for parts as well as rebuilding.

You may wish to buy the used ones and give them a try first as that be less trouble than rebuilding and cost the same as buying the rebuild kits.

What year and model MB is this?

gmask · #3 10-04-2002, 02:32 PM

Oh I see 74 250.. how much experience do you have under the hood? Why do you think you need to rebuild the ones you have?Maybe your car just needs a tuneup?

ctaylor738 · #4 10-04-2002, 08:28 PM

Why do you think you need to do a rebuild?

What are the problems you are experiencing?

Most Zenith problems are caused by un-synchronization, or warpage due to the heat risers sticking open, or a malfunctioning fuel return valve.

None of these problems will be helped by a rebuild.

Please describe the problems you are having.

#5 10-05-2002, 12:22 PM

Thanks Chuck..is that the same part # for a 108 280S?.......Speaking of Fuel Return Valve, I working on my 108's Carbs and the valve is shot. Does anybody make a rebuild kit for them?

ctaylor738 · #6 10-05-2002, 02:08 PM

Just looked at the parts book for the 250C, and it shows the valve and all of its internals as parts. Group 07/1, #'s 174 - 179. I would try Rusty at *************** or a MB dealer with a really good and patient parts department.

peebeeNZ · #7 10-05-2002, 05:15 PM

The reason I am enquiring is one of the accelerator pumps is seized , the other only dribbles and the main housing is loose from the base on the rear carb. Since I have to remove one carb from the manifold to tighten it up I was looking at my options. I dont want to have to repair the carb 6 months down the track due to not rekitting or replacing now while they are off the car.
Peter

psfred · #8 10-05-2002, 06:12 PM

Peter:

Replacing the accelerator pumps requires enough disassembly that you might as well go ahead and do the whole thing. Minor kit is all you need, contains gaskets, needle valve seat and valve, accel. pumps, etc.

Cost is going to be about the same if you have it done, pain and agony getting them going yourself, ditto.

I've rebuilt quite a number of carbs (American), so can tell you that it isn't that hard if you have good instructions and don't lose and small bits. Life becomes much more difficult if you drop something and cannot find it, or the instructions don't make sense.

Unless the replacement carbs are off a car in excellent running condition, you will probably want to rebuild them anyway -- if they sit for any length of time, bad things happen to them, mostly leaks from dried out gaskets and leaking needle valve seats.

Peter

Peter

#9 10-05-2002, 08:23 PM

Please check a couple lines up for edit..

ctaylor738 · #10 10-05-2002, 09:34 PM

You don't need to remve the carb to tighten against the base. You remove the top plate and then there are 4 (?) additional screws that hold the fuel block (center section) to the base. I am not sure how these would come loose, though.

You can get at almost all the reubuildable components in these carsbs by removing the top plate and the fuel block. A cardinal rule is to fix only what does not work - specifically, do not charge into the vacuum operated secondaries if they are working.

If one accel pump is weak and one is frozen, it sounds like the little venturi tubes are almost and completely clogged (respectively). The pumps themselves have a rubber or leather "skirt" that is unlikely to sieze.

I would recommend the following for each carb:

Leave the carb on the manifold. Remove the top plate and fuel block, taking care to save the gaskets. If they are OK, you may be able to address your accel pump problem without a kit by simply cleaning out the tubes with a thin wire. You can also remove all of the various jets and orfices, clean them and reinstall.

If you cannot save the gaskets, or want to do a complete rebuild, the kits are about $35 US.

If you would like a copy of the relevant section of the CD, send me an email and I will send it to you.

gmask · #11 10-05-2002, 09:36 PM

Quote:

Originally posted by ctaylor738

If you cannot save the gaskets, or want to do a complete rebuild, the kits are about $35 US.

Where did you get this price? The quotes I have gottern where around $45-50 each.

ctaylor738 · #12 10-06-2002, 11:58 AM

www.*************** has them.

peebeeNZ · #13 10-06-2002, 07:17 PM

I got 2 carbs off a Wrecker. I had the chance to hear them on the car while it was still cold and they sounded good. No hesitation or missing. Pulled the old ones off and put the new ones on. It took about 1 1/2 hours to do. Started the car up and it has never sounded better in the year that I have owned it.
Upon a quick investigation of the old ones I see that one of the screws in the throttle valve housing was missing and the other three were loose. These are screwed in from the bottom so I guess some previous owner has done a botch up job. there is no way that they can fall out while the carb is in place. I guess that would have caused a vacum loss in their operation.
I would like to thank all who contributed and I will soon start considering my next operation on the rear oil seal which sounds like a biggie.

Peter

ctaylor738 · #14 10-07-2002, 08:29 AM

U da man!

To keep your new carbs in good shape, suggest you make sure that your heat risers are working correctly, or at least stuck in the shut position. Otherwise, they will funnel heat to the carbs and cause them to warp = vacuum leaks.

#15 11-05-2002, 12:14 AM

Zenith carbs: Hideous things. Went through 2 sets. Warped quickly and badly and ran rich . In 1998 When I restored my wife's '70 250C she's owned since 11/70 replaced them with Webers from Jam Enineering, Monterey, CA which makes a total kit set & jetted specifically for the M130.923 engine. My mechainc bolted the kit on adjusted some settings and I drove away quite satisfied.

Result: trouble free, and an engine at idle that's almost as smooth as an injected engine.