Carbs rebuild - Page 2 - Mercedes-Benz Forum

Reply
 
LinkBack Thread Tools Display Modes
post #11 of 40 (permalink) Old 08-16-2013, 06:14 AM Thread Starter
BenzWorld Extremist
 
kavadarci's Avatar
 
Date registered: Aug 2008
Vehicle: 1971 250C
Location: Toronto, Canada
Posts: 1,056
Mentioned: 0 Post(s)
Quoted: 14 Post(s)
(Thread Starter)
Thank you
I do have leak there and will be taking out


Sent from AutoGuide.com Free App
kavadarci is offline  
Sponsored Links
Advertisement
 
post #12 of 40 (permalink) Old 08-16-2013, 09:07 AM
BenzWorld Elite
 
rumb's Avatar
 
Date registered: Oct 2012
Vehicle: 1968 250S, 1991 300se, 1998 SL500, 2x 1977 450SEL 6.9. Past MB's; 300SD, 300E, 300TE, 190E, ML420
Location: Colorado
Posts: 2,351
Mentioned: 5 Post(s)
Quoted: 425 Post(s)
Garage
http://www.benzworld.org/forums/vint...sources-3.html

lots of good info from grubguy.

The return valve is a bit hard to repair. I have developed a way to rebuild them with new gasket and a bit of machining. PM if you are interested in buying one from me.

These valves are not available anywhere including MB classic center.
rumb is online now  
post #13 of 40 (permalink) Old 08-16-2013, 09:19 AM Thread Starter
BenzWorld Extremist
 
kavadarci's Avatar
 
Date registered: Aug 2008
Vehicle: 1971 250C
Location: Toronto, Canada
Posts: 1,056
Mentioned: 0 Post(s)
Quoted: 14 Post(s)
(Thread Starter)
Thank you.
I have confirmed the place have had multiple zenith carbs rebuild and they just did two for Mercedes dealership last week.
Bench flow testing is part of the rebuild and it takes two weeks.

I will be checking the return fuel valve and if it doesn't work I'll send you pm rumb.
kavadarci is offline  
post #14 of 40 (permalink) Old 08-16-2013, 06:58 PM Thread Starter
BenzWorld Extremist
 
kavadarci's Avatar
 
Date registered: Aug 2008
Vehicle: 1971 250C
Location: Toronto, Canada
Posts: 1,056
Mentioned: 0 Post(s)
Quoted: 14 Post(s)
(Thread Starter)
Quote:
Originally Posted by Over 75 View Post
Kavadarci. Your gas smell could very well be caused by a non- functioning fuel return valve.[ File Type: pdf Zenith Fuel Return Valve.pdf (123.8 KB, 116 views)] When you shut your engine off, the fuel is supposed to return to your tank. If the membrane is leaking and does not open, you will smell it all over the place. Gas will slowly leak on the tray below your carb and evaporate. Getting a new one from Uncle Benz is costly,
about $ 375 can. I rebuilt my own with a cut to size 40mil. rubber membrane. It might solve yor problem. Perhaps your rebuild guys have that part. Harald

Harald,

so let me see if i have this clear, when the engine is off and idling the valve should be open, the minute you press on the gas, it should close, correct?
and is it opened when it is pushed up or when it's down?

so i checked the return fuel valve and it was all covered in gas, took all out cleaned and put back. all looks nice, the gasket is intact, that is sure one hell of gasket to repair. mine is good.
i noticed the dual leaf springs that open or close the valve were both on top of each other and once i press the gas the fuel return valve doesn't close.
in other words mine was always open.
i reworked the leaves springs and adjusted the screw so the minute the gas is pressed the valve is closed.


I drove the car with no filters and didn't feel the smell.
i put the k&n filters and will be driving tomorrow to see if this works.
I will do Luna's fix and that should get me going.
HUUUUUUUUUUUUUUGE difference on the engine response with the k&n

Thank you
kavadarci is offline  
post #15 of 40 (permalink) Old 08-16-2013, 10:02 PM
BenzWorld Member
 
Date registered: May 2013
Vehicle: 1961 190SL
Location: Northern California, USA
Posts: 136
Mentioned: 0 Post(s)
Quoted: 0 Post(s)
Gentlemen,

I've read this topic with interest. It's been my experience that there is not a single mechanical device on a car, including carburetors, that a motivated amateur cannot service in a completely satisfactory way. I'll be the first to admit that I've not opened up a Zenith carburetor since I had a Model A Ford with one in 1960. But all modern carburetors are complicated and require that all the adjustments be made in the sequence specified in the instructions that come with the kit, or they will not work properly. How complicated can it be to follow a set of simple, well illustrated instructions?

As for bushing the throttle shaft bores, that's hardly rocket science. The shafts and throttle plates are removed, a straight rod placed through the shaft bores and chucked in a drill press or milling machine, the carburetor body is then clamped in a vise secured to the table to assure bore concentricity with the machine spindle, a sharp, straight drill is used to increase the hole size to the bushing OD, the bushings are pressed or tapped in and the shafts and throttle plates are reinstalled.

It's amazing to me that anyone would pay $500 to have 2 carburetors disassembled, soaked in solvent, the passages blown out with compressed air, and throttle shaft bushings and kits installed. Wow, that's really easy money!

Dan's Zenith invention sounds really interesting even though the carburetors on my vehicles are Weber, Carter Thermoquad, Carter W-1, Rochester Quadrajet and Edelbrock AFB clone manufactured by Weber. Except for the Webers on my wife's 190SL these carburetors have all had their jetting optimized by seat of the pants tuning and plug reading and work very well.

Here's a link to an interesting article on plug reading. There are others like it too.
Spark plug reading

Ray W
Waldbaum is offline  
post #16 of 40 (permalink) Old 08-17-2013, 04:08 AM
BenzWorld Member
 
Luna Gaudi's 72 250's Avatar
 
Date registered: Sep 2012
Vehicle: 1972 Mercedes Benz 250
Location: Santa Fe, NM U.S.A.
Posts: 389
Mentioned: 0 Post(s)
Quoted: 17 Post(s)
My experience with the fuel return valve is this. Mine was leaking a few drips every minute and I did not want leaking fuel anywhere near the exhaust manifold. I took apart the valve and the diaphragm inside was not damaged, I put it back together again, tightened it down and it did not leak for a couple of days, then the leak returned. I took it apart again and this time sealed it with some fuel resistant sealer. Put it back together again and this time it did not leak for about seven days. I went on this forum and found an old thread about completely sealing it in the open position. The info on the thread helped me to decide to seal it open with some JB weld (which is fuel resistant) The discussion theorized that the amount of fuel that would be returning to the tank was not enough to hurt the performance at full throttle. I have been driving the car like this since April and have not noticed any lack of fuel to the carbs at highway speeds. The car will easily get up to 80 mph and hold steady there. The best part is that the leak is permanently gone.
Luna Gaudi's 72 250 is offline  
post #17 of 40 (permalink) Old 08-17-2013, 07:09 AM Thread Starter
BenzWorld Extremist
 
kavadarci's Avatar
 
Date registered: Aug 2008
Vehicle: 1971 250C
Location: Toronto, Canada
Posts: 1,056
Mentioned: 0 Post(s)
Quoted: 14 Post(s)
(Thread Starter)
The full repair kit is $34 bucks.
I know i can do that but i know i can't bench test for flow and make sure is all per specs

Your Parts Search Returned 1 Part(s)
kavadarci is offline  
post #18 of 40 (permalink) Old 08-17-2013, 07:26 AM
BenzWorld Elite
 
LWB250's Avatar
 
Date registered: Jan 2013
Vehicle: 90 350SDL, 98 S420, 97 SL500, 94 S420, past owner of W108/W112/W114/W123/W124/W126/W140 & W220 cars
Location: Tampa, FL
Posts: 4,409
Mentioned: 8 Post(s)
Quoted: 628 Post(s)
Quote:
Originally Posted by Waldbaum View Post
Gentlemen,

I've read this topic with interest. It's been my experience that there is not a single mechanical device on a car, including carburetors, that a motivated amateur cannot service in a completely satisfactory way. I'll be the first to admit that I've not opened up a Zenith carburetor since I had a Model A Ford with one in 1960. But all modern carburetors are complicated and require that all the adjustments be made in the sequence specified in the instructions that come with the kit, or they will not work properly. How complicated can it be to follow a set of simple, well illustrated instructions?

As for bushing the throttle shaft bores, that's hardly rocket science. The shafts and throttle plates are removed, a straight rod placed through the shaft bores and chucked in a drill press or milling machine, the carburetor body is then clamped in a vise secured to the table to assure bore concentricity with the machine spindle, a sharp, straight drill is used to increase the hole size to the bushing OD, the bushings are pressed or tapped in and the shafts and throttle plates are reinstalled.

It's amazing to me that anyone would pay $500 to have 2 carburetors disassembled, soaked in solvent, the passages blown out with compressed air, and throttle shaft bushings and kits installed. Wow, that's really easy money!

Dan's Zenith invention sounds really interesting even though the carburetors on my vehicles are Weber, Carter Thermoquad, Carter W-1, Rochester Quadrajet and Edelbrock AFB clone manufactured by Weber. Except for the Webers on my wife's 190SL these carburetors have all had their jetting optimized by seat of the pants tuning and plug reading and work very well.

Here's a link to an interesting article on plug reading. There are others like it too.
Spark plug reading

Ray W
Ray,

While I would not take exception to your comments, they make the assumption that the OP has access to the required tools, equipment AND experience to perform these operations, which they may not.

Also, while something as simple (to you) as rebushing a throttle shaft might be an hour in the garage on a Saturday afternoon, for someone who has never done this the level of confidence is very low, not to mention the potential for a very expensive and potentially catastrophic failure being quite high.

As a former NIASE certified mechanic who made a living working on high line cars, I recognize the value that a competent and professional repair has for an owner who might be reluctant to take on what you or I might deem a "simple job."

I have rebuilt many Zenith carbs, and while $250 to do so might seem extravagant, I can easily justify the expense based on accumulated knowledge and the cost of the equipment to test and adjust the carb.

Having the carbs bench and flow tested is a big plus - that's not something one can do at home, and it eliminates a lot of possible concerns during the setup and adjustment.

Based on what i know about "retail" carb rebuilds/repairs, I think $250 is reasonable considering the value the OP is getting for the money. Not only that, the responsibility for proper operation and repairs now falls at the feet of the rebuilders. If it was you or I that is our time trying to figure things out. In this case the OP has transferred that responsibility to the rebuilder for a fee.

In this day and age I'm surprised one could even find someone to rebuild these carbs. I say "Go for it!" and get the car running well.
LWB250 is online now  
post #19 of 40 (permalink) Old 08-17-2013, 11:50 AM
BenzWorld Member
 
Date registered: May 2013
Vehicle: 1961 190SL
Location: Northern California, USA
Posts: 136
Mentioned: 0 Post(s)
Quoted: 0 Post(s)
LWB250,

Thank you so much for your thoughtful response. The greatest gift that has even been given to me in the car hobby is the encouragement that others have given me to try things that I don't know how to do.

For example, when I restored my 1936 Chevy pickup in the 1970s I straightened all the metal myself without any bondo but when it came time to apply the color coats I was intimidated because I'd only shot primer. The dad of one of my buddies was an old, experienced body man and he had this to say about my fear of spraying color: "You won't learn any younger".

It was tedious at first and I only sprayed little stuff like wheels, taillight buckets and headlight buckets. As my confidence increased I moved on to fenders, the pickup box, the hood and finally the cab. I belive that on technical forums like this those of us who have done the tasks that others are looking at can, and should, offer encouragement.

Carburetors are stone age devices. They are castings into which interchangable metering orifices are installed. The best "flow test" that I can imagine is actually running one. It doesn't matter how a carburetor works on some test device. What matters is how it runs on its intended application. It is no accident that my carbureted vehicles run much better after my trial and error rejetting than they did with the factory installed metering orifices. These alterations are illegal in California but the vehicles now are more powerful, run cooler and get better gas mileage. This was accomplished by simple trial and error and plug reading.

I am far from the sharpest knife in the drawer. So, I figure that if I can do it anyone can do it. Sometimes all a person needs is a little encouragement to give it a try.

By the way, the home restored '36 chevy pickup won at a national Chevy meet after being driven 1300 miles to the meet and competing against trailer queens brought there in enclosed trailers. So, there's a case where a motivated amateur defeated the efforts of the big bucks "pros". So, lets drink a brew to the hobbyist!

Ray W
Waldbaum is offline  
post #20 of 40 (permalink) Old 08-17-2013, 12:09 PM
BenzWorld Member
 
Luna Gaudi's 72 250's Avatar
 
Date registered: Sep 2012
Vehicle: 1972 Mercedes Benz 250
Location: Santa Fe, NM U.S.A.
Posts: 389
Mentioned: 0 Post(s)
Quoted: 17 Post(s)
Quote:
Originally Posted by Waldbaum View Post
LWB250,

Thank you so much for your thoughtful response. The greatest gift that has even been given to me in the car hobby is the encouragement that others have given me to try things that I don't know how to do.

For example, when I restored my 1936 Chevy pickup in the 1970s I straightened all the metal myself without any bondo but when it came time to apply the color coats I was intimidated because I'd only shot primer. The dad of one of my buddies was an old, experienced body man and he had this to say about my fear of spraying color: "You won't learn any younger".

It was tedious at first and I only sprayed little stuff like wheels, taillight buckets and headlight buckets. As my confidence increased I moved on to fenders, the pickup box, the hood and finally the cab. I belive that on technical forums like this those of us who have done the tasks that others are looking at can, and should, offer encouragement.

Carburetors are stone age devices. They are castings into which interchangable metering orifices are installed. The best "flow test" that I can imagine is actually running one. It doesn't matter how a carburetor works on some test device. What matters is how it runs on its intended application. It is no accident that my carbureted vehicles run much better after my trial and error rejetting than they did with the factory installed metering orifices. These alterations are illegal in California but the vehicles now are more powerful, run cooler and get better gas mileage. This was accomplished by simple trial and error and plug reading.

I am far from the sharpest knife in the drawer. So, I figure that if I can do it anyone can do it. Sometimes all a person needs is a little encouragement to give it a try.

By the way, the home restored '36 chevy pickup won at a national Chevy meet after being driven 1300 miles to the meet and competing against trailer queens brought there in enclosed trailers. So, there's a case where a motivated amateur defeated the efforts of the big bucks "pros". So, lets drink a brew to the hobbyist!

Ray W

+1 on that! Congrats on the win.
Luna Gaudi's 72 250 is offline  
Sponsored Links
Advertisement
 
Reply

  Mercedes-Benz Forum > General Mercedes-Benz Forums > Vintage Mercedes-Benz

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Mercedes-Benz Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in











  • Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
     
    Thread Tools
    Show Printable Version Show Printable Version
    Email this Page Email this Page
    Display Modes
    Linear Mode Linear Mode



    Posting Rules  
    You may post new threads
    You may post replies
    You may not post attachments
    You may not edit your posts

    BB code is On
    Smilies are On
    [IMG] code is On
    HTML code is Off
    Trackbacks are On
    Pingbacks are On
    Refbacks are On

     

    Title goes here

    close
    video goes here
    description goes here. Read Full Story
    For the best viewing experience please update your browser to Google Chrome