Carburettor Help needed

jaymanek

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Hi Guys,

I had my manifold changed on my 123 200 Engine last week. Now i have a problem with the carb...I cant seem to set it right.

Before i changed the manifold, the car would always hesitate a little untill it warmed up to 60 or 70....but only a little.

Now it doesnt even like me touching the accelerator untill its warmed up. Its quite dangerous when trying to pull away, as you need to pump the accelerator a few times before it gains enough energy to go anywhwere....

its ok after warmed up, maybe a tiny bit jerky and hunts a bit, but ok...

I have done a slight bodge job, in terms of fitting an 'idle compensator from an auto car that i have sitting in my driveway, this keeps it from cutting out altogether...i realise this should not be fitted on a manual, but it keeps the car going in traffic..

I tried to adjust the co myself while i was at the garage, but didnt have much time and i think i managed to set it to about 2, book quotes 1.5 but someone told me thats a bit too lean for that engine.... Also while i was adjusting that, the carb started to leak petrol, but hasnt shown any signs since then....

Im no expert, but i want to get this sorted.... I have a good workshop manual and so far have discovered that i dont have a preheater thingy, theres an original looking blanking plate where that should be...

Any insight kindly appreciated...If not, then to George Fraser on saturday, but really dont want to spend more money at the mo!
 

Ian B Walker

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sounds a little like your needle is sticking, I may be wrong but check it out. I had a similar problem in mine, ie, fuel comming out of the carb. Another think to look for, do you have any air / vac lines going to the carb? and have you got them fitted the right way round?
 
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jaymanek

jaymanek

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Hi,

thanks Ian

There isnt that much vaccuum stuff going on really, i think its correct, but not sure and i cant find any diagrams. I have a good manual, but doesnt show the vaccuum pipes clearly. I tried to copy the setup of my other 123-200, but that has a slightly diff carb and the newer engine...

Also there is a small circular unit thing on the inner wing, has an electrical connection and two vac pipes coming out of it. I dont know what this does so not sure where to put the pipes????

Im not sure i want to take the carb apart in london, as there is a lack of any dealers, or even halfords close to me to get emergency supplies, so i think i will leave that bit to George Fraser on Saturday.

Any help on the vac pipes would be appreciated!

Cheers
 
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jaymanek

jaymanek

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Hi can anyone see anything wrong with the vac connections? The one that ive blanked off- i cant see where it goes....

Carb-Vac.jpg



Thanks

Jay
 

Brian WH

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The circular thing as you call it is the vacuum diaphram.

If I were you I would leave any messing about to George, as he will have the test equipment to set it all up mate.
 

Sp!ke

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I must say that your symptoms do sound like the problem relates to your carb rather than anything else. The carb looks like an old Bing diaphagm type....you have checked for splits in the diaphragm haven't you?

Failing that, I would strip the carb (again?) and double check that all the jets are clear if the problem relates to tickover, maybe the pilot jet is blocked...blow through everything to make sure all passageways are clear ...if in doubt blow smoke and you can tell where the flow leads. Also, double check the float for sticking and height.

In terms of setting the mixture, the best tuning method on an old girl like this is your ears...the optimum setting is at the point at which your engine ticks over fastest ;)

Brians right on the old vacuum diaphragm, they are often found linked to old points ignitions and are used to act as primitive advance/retard units (now replaced by very expensive black boxes) but in your case it looks like its linked to the carb so perhaps its some kind of enrichment mechanism??? Did you set the diaphagm up carefully on reassembley?

hmmmm thats got me thinking.... this could be linked to the ignition timing.... Mebbe you should check the timing - statically if you havn't got a strobe light but best to use a strobe and make sure the ignition is advancing and retarding correctly.

I got a strobe somewhere if you are desparate!
 
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jaymanek

jaymanek

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Hi Spike, thanks for that, no I havent taken any screws off, as I was hoping for something simple as it worked okish before the manifold change... will get my tool box out tonight and look for splits....

Thanks

jay
 
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jaymanek

jaymanek

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Well ive decided im going to rebuild the carb!

George Fraser did a bit of setting up, i.e timing was out so that was set, then he tried to set the CO, but kept jumping around, eventually got it set at 2.5, but didnt seem right when i started driving, was really holding back, and the next morning, took a while to start.

Then i used spikes method to adjust the CO, i.e setting it to the point the engine revved most. Worked well, now like runs nicely when warmed up, but still very hesitant untill it reaches full operating temp.
Idle, by the way, is perfect now, must have been timing.

Anyone guess why im only having problems when cold??? I have set the autochoke up perfectly now, starts at around 1300rpm when cold and goes down slowly...not as perfect as modern autochokes, but at least it does something now!

Unless anyone advises otherwise, i am going to buy a repair kit and rebuild with new needle, jet, o-rings etc. Never done before, but armed with my Brooklands manual and some stuff i found on the web...

Any insight much appreciated.
 

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