My 123 Carb again

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jaymanek

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Hi all,

Well after i have completely reconditioned the carb, its not running that much better than before! After speaking to some 123 experts, they reckon if i can get my carb to set correctly with my 115 engine, ill be the first in the country!

Anyway, i have another related problem...

At the traffic lights sometimes, it randomly just cuts out, if i press my foot hard on the accelerator i can get it to come back, but it runs rough for a few seconds, then itll be ok untill the next time it idles...

It never does it at high revs...i went to oxford yesterday and was excellent on the motorway...

Ive got a feeling its fuel starvation (because if i accelerate i can save it from dying) and so something to do with the return pipe, maybe its returning too much?? Maybe i messed something up when putting the carb back together??

Theres no electronic fuel pump in my model, so that ruled out...

Any help much appreciated!

Jay
 
Sounds to me like an air leak Jay.

However I don't know enough about your engine or carb to be sure, but the symptoms are pointing me in that direction.:confused:
 
hmmm, its finding it! I need to find someone who can pay full attention to this and get it sorted once and for all.....

Ill see if i can spot anything.. maybe one of the gaskets didnt sit right or somethin when i put it all back together...
 
Ok im losing patience with my 123... im using it every day as im still looking around for another car.

Does anyone know someone decent around london who could spend a bit of time sorting out this problem. My carb needs to be looked at and also i think i have an electrical problem as its misfiring sometimes and generally being a pain up the backside...

Tried setting timing etc, but im no expert...

Doesnt matter even if its just someone with a garage in his back garden, this is a really simple engine, just need someone who would know what to do and has some time to do it!

Jay
 
Pity you are not in this part of the world Jaymanek as i could point you to a guy in Blckpool who is a wizard
 
one any other car that would realy sound like an air leak.

so check any pipes connected to the maifold and check all gasgets.
 
Deffinately air leak into the manifold. This will have the greatest effect at idle on a warm engine.

Spray around all the gaskets with an oil aerosol when idleing as the oil will be drawn into the offending joint and produce smoke.

Alternatively buy a vacuum guage for a few quid. You will then be able to observe your vac at all operating conditions and can even set the mixture and timing with it!
 
right! aerosol - good trick...never thought of that! cheers...

As for vac guage, kinda lost me on how im gonna set timing and mixture... am i looking for greatest vac at optimum mixture??

And can i get a vac guage from any motor factor or is it a snap on type jobbie..

Cheers

Jay
 
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Vac. guages are dead cheap available from any motor parts shop. Under a tenner.

To set the timing and mixture you simply obtain the highest vac when driving at any given speed on a flat road.

If you are really struggling with the carb take it to the carburettor centre in Leicester when you're next in Coventry. 0116 2855010
 
Thanks, i go to leicester a lot so thats really useful... cheers..

Will it not work if i set it at the highest vac when idling??

Cheers

Jay
 
You can set the idle mixture this way, but if you have an induction leak the mixture will then be too rich while driving, as you will have compensated for an air leak.

You cannot set the timing with a vacuum guage unless the engine is under load. The timing will be too far advanced if you set it when idleing.

The carb. cantre is on Shaftsbury Road, off Narborough road near J21.
 
if the mixture is too rich while driving, does it splutter and missfire... if so, then i definately have an air leak! When i set the co at idle, its fine, then when driving, still not performing...

Ok so im gonna get a vaccuum guage and do as much as i can, then when i next go back to cov im goin to leicester!


Thanks for all your help mate..

Cheers
 
An air leak could cause this at small throttle openings but as you open the throttle the air leak reduces as the manifold depression falls.

Other causes could be a poor (low voltage) spark or mixture too lean for other reason, such as blocked jet or emulsion tube, float set too low, fuel pump pressure inadequate causing the float chamber to empty as fuel is used.

Check the spark using a spark tester or holding an HT lead an inch from the head, the spark should jump ok. 25Kv to an inch IIRC.

Fuel pump pressure can be tested or can be deduced by the car starting driving Ok and then spluttering when the engine is revving high or under load, as the pump cant keep up with the amount of fuel required.

I don't know if your car has a condensor and points, if so suspect the condensor.
 
has condensor and points, i am going to change as this is one of the things i havent done...

Float level, dont remember setting this! maybe i should try increasing the float level..

The car runs better if you dont give it too much throttle, esp when cold, if you put your foot down it holds back...

I think the fuel pump is ok and have put new dizzy cap, rotor arm, leads and plugs recently, so cant see it being that...

The only thing that could be wrong is the float or an air leak from what youve mentioned, i did put a new float in and a new valve that came in the carb rebuild kit. I think i set it so that it would cut fuel suppy when float was about horizontal, but cant be sure! Means taking the whole bl**dy carb off and apart again!

Want a job for the weekend?? :D

Cheers

Jay
 
Nice try Jay.

This sounds like the mixture is too lean, especially under load. Check the float height and that you've built the "power Valve" correctly.
 
hee hee :p

Is the power valve the thing the float controls? Hopefully get some time on sunday to play....

Cheers

Jay
 
Power valves are a small diaphragm that allows mixture enrichment when there is no manifold vacuum, ie. WOT.

Also make sure there is a sqirt of fuel from the accelerator pump when accelerated hard. You can check this without the engine running.

These devices are for fixed venturi carbs. Sorry Jay not sure what you have. If it's variable venturi (stromberg type) then the needle controls all the mixture.
 
Ok i think i know what you mean, and mine doesnt have it, its a little thing on top near the autochoke that has a vac pip going to it. Mines a Stromberg 175CD, the Pierburgs (used on the newer engines after late 1980) have it and always wondered what it was for.

I was at a mates place the other day and he mentioned he had a merc engine round the back, so went to have a look and it was the 2ltr engine made after mine, i.e 1981 model engine. Has the newer Pierburg carb... He said i was welcome to the carb... So ive got it, but seems quite seized up... Apparently the engine ran superbly but has been sitting for a while and so ill need to try and free this carb up... i dont think ill take it all apart for now as i dont want any leaks or mistakes when i put it back together..

Anyway so im gonna have a mess around with the exsting carb, but if i dont get anywhere, might try my 'spare'...

Thanks for all your help dieselman and i will get back once i get a day to play...

Cheers

Jay
 
Jay

Strombergs are simplicity itself. Most faults are caused by one of three things; jet set too high causing lean mixture, float incorrectly set or split diaphragm.
Make sure the dashpot is not overfull and that the oil isn't too thick.
 

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