Solex gas pooling...what the ? - PeachParts Mercedes-Benz Forum

blankenship · #1 05-26-2009, 06:57 PM

i've noticed some gas pooling in my solex carb in the area shown in the attached photo...

it fills up a little there when running, and then leaks down the side of the carb.
i cleaned the jets and didn't help.

any ideas what could be causing this?

mbbuff · #2 05-26-2009, 09:45 PM

Does it run OK, or is it loading up (rich)? Could be the float adjustment is not set correctly, or as in my case, the float was bad. That made it run rich, load up, hard starting, etc. New floats are available from your knowledgeable local import parts store for about $45....dealer might be more. Also, you can take the top off without removing the carb. which makes it an easy job.

blankenship · #3 05-28-2009, 05:06 PM

the plugs on cylinders 1-3 are all nice and tan.
the plugs on 4-6 are black and carbony.

it's weird...the "gas pooling" seems to come and go...like it'll happen one day, and not the next.

usually in the morning she'll start and then die once or twice unless you keep your foot on the gas a bit.
she idles smoothly, but ocassionally at a stoplight will gradually decrease in RPM's until dying (again, unless you give her a little gas).

thoughts?

ja17 · #4 05-28-2009, 07:21 PM

Hello,

Sometimes the brass seat for the float needle valve comes loose in the carb top. It then moves up or down intermittantly causing sporatic float level problems. Check this if your float turns out to be good.

blankenship · #5 05-29-2009, 07:51 PM

well, took her apart today:

that float needle valve seems secure. i basically tried to wiggle and turn it and pull it out with my fingers, and couldn't. i assume that means it checks out okay>

the float LEVEL, though, is posing problems:
the books says so depress the short end of the float arm (such that the float rises), and then measure the distance from the carb plate...but from the carb plate to WHAT? it specifies 7mm, but when i measure from the carb plate to the fuel level, it's 18mm. when i measure from the carb plate to the top of the float, it's 2mm. what the ?

Arthur Dalton · #6 05-29-2009, 09:43 PM

When you push on the short arm and the float is at the fuel off position, does it look fairly level??

mbbuff · #7 05-30-2009, 09:47 PM

The measurement is from the carb. parting (top of carb. body) surface (without the gasket in place) to the top of the float. It also depends which float you have. There is a flat top one (old style, 8.7g wt.) and a "hip roof" one (new style, 6.8g wt.) with a small recess on the leading edge used as the measuring point. The new one, being lighter, is more bouyant and increases the closing force on the needle valve. The shop manual shows 0 to 2 mm for the new type, and -2 to 6mm for the old type. Try to keep the measurement on the higher side, if possible. Too low will cause transition (from idle to power) and start problems. If you have to readjust more than once or twice, buy a new float. Also, if you have the old style, buy a new one. Mine acted very similar to yours (erratic) until finally I couldn't keep it in adjustment at all.

blankenship · #8 05-31-2009, 02:49 PM

well, i definitely have the "new style / hip roof" float...

my float/arm is pretty darned level...measures 2.0mm from the carb "parting plate."
i'd said the float level spec is 7mm because my Haynes manual (which covers the 250 and 280 w123 series from 1976-1984) says :

Quote:

Float level:
110.923, 110.924 engines.................2.0 mm
Except 110.923, 110.924 engines........7.0 mm

Since I've got a 123.920 engine, i figured mine fell in the 7.0 mm category. But I can't find confirmation of that specification ANYWHERE on the web.

What manual did you get your "0-2mm" spec from, MBBUFF?
Anybody have a good online resource for specs on the Solex 4A1?

I'm now guessing 2mm is the spec, and that my Haynes manual is wrong...just because I can't imagine my car running at all decent 5mm outside the parameter. I mean, it has a good deal of power, doesn't foul plugs, but...on the other hand, failed the emissions test miserably)...

mbbuff · #9 05-31-2009, 05:58 PM

My info. comes from the MB Service Manual for the 110 engine, Volume One. I can't imagine the 7 mm spec. as I think it would be way too low, causing a transition flat spot and start problems. The "book" says to go with the higher level, if possible to avoid these issues. My float and arm are also pretty level. On your emissions test, is everything else in the ignition system (plugs, points, condenser, cap, rotor, wires, timing, vacuum advance, emission crap in fender well) all hooked up properly and in good order? Any other carb. issues? Is the choke coming off completely? Is the air cleaner element clean? If all the above is good, you can retard the timing, and lean out the idle mixture (turn each mixture screw in) until the engine RPM starts to drop. Before starting the engine for this check each screw's current position (number of turns out from bottoming out) and make sure they are the same number of turns out. i.e. You don't want one side out one turn, and the other one out two turns. Then move each one the same amount. If this doesn't get you past the test, you can sometimes fudge a little by creating a small vacuum leak that won't be obvious to the inspector. Also, if your vacuum advance is no longer hooked up to the fender well emission stuff, you may want to stick a BB in the vacuum line to keep it from operating during the test. Just remember to take it out when you're done. You also said some plugs look good, and others look "rich". You may have some bad spark plug wires, and/or fouled spark plugs. I've found that NGK BP6ES plugs work the best for me. A new set of wires would run about $70. Have you done a compression check? If so, what are the numbers? Are you having fun yet?

mbbuff · #10 05-31-2009, 06:04 PM

You said your car is a 77 280E?? "E" is fuel injected, gasoline. Your chassis number should be 123.033, and the engine a 110.984. Has someone changed something on this? A friend of mine had the same year/model and his was fuel injected. Where are you in the Northwest? I am in Boise.

blankenship · #11 06-01-2009, 06:24 PM

it's actually the 1980 euro 250..it has a M123 engine (123.920), and is carbureted w/ the Solex 4A1. due to the "euro" designation, she's got no emissions stuff to speak of. they don't visually check anything at the inspection place except catalytic converter (which she does have).

transistorized ignition...good cap/rotor/wires/plugs/compression, etc.
mixture screws are both "out" about 1-1/4 turns.

taking the carb apart a couple days ago to inspect the float seems to have solved the disparity between the rich/lean plugs...
main problem now is a new one: hard starting, and she'll idle in P or N, but dies the second you put her in drive!

thoughts on that?
also, what do screws 1 and 2 do in the attached photo?

ps: i'm in Portland.

MunichTaxi · #12 06-02-2009, 01:32 AM

and she'll idle in P or N, but dies the second you put her in drive!

That sound like a vacuum leak. Were all the vacuum hoses re-installed?

mbbuff · #13 06-02-2009, 11:34 PM

My shop manual doesn't show anything quite like your Solex. It does show one version that has a, "Thermostatically Controlled Auxillary Bypass Choke (TN)", and also a "Vacuum Controlled Float Chamber Vent Valve". I think the position of that is about where your big black chamber in front is located. Yours looks like it is electrically controlled though. Anyway, the TN choke shows two screws, a TN mixture Adjusting screw and a Lean Volume Adjusting screw. They are not situated exactly where yours are, but perhaps that is what these are for. Maybe someone else can shed some more light on this. Sorry I couldn't be of more help.

blankenship · #14 06-04-2009, 07:49 PM

1. it seems the "dies when shifting into drive" problem was cured by enriching the two 'CO mixture screws.' also, the book answered my question about 'uneven running' from spark plugs 1-3 and 4-6...the mixture screw on the "right" controls cylinders 1-3, and the one on the left controls cylinders 4-6.

QUESTION::: what's the likelihood of finding the perfect position for those screws shy of having a "CO measuring device" hooked up as my book suggests? Should I basically be doing a 'trial and error' on the screws until the spark plugs look good and she's running nicely? Right now, both screws are roughly 1-3/4" turns "out."

2. i've tried a number of times to set-up the correct relationship b/w the idle screw and the vacuum regulator, but my book describes it in a ridiculous way, and i have no tachometer.

QUESTION::: Anybody got a good 'down and dirty' way to get all that set nicely?

3. i've SCOURED the internet, and can't find ANYTHING that describes what the two screws i showed in this picture do. the bigger, top screw is "out" 10 turns. the smaller, lower screw is "in" all the way.

QUESTION::: If anybody has more info on what they do, or what's up with this TN Choke business MBBUFF is talkin' bout, i'd love to hear it!

mbbuff · #15 06-04-2009, 10:25 PM

On adjusting the idle mixture screws, I've always used a vacuum gauge. They both should be out about the same amount, like yours are. I always adjust to the highest vacuum reading. Turn one at a time in until the RPM and vacuum starts to fall and then out to the highest vacuum reading. Do the other one the same way. This should give you the best idle quality, but WILL NOT give you the best setting for emissions. If Oregon has emission testing you'll have to change them for the test. When I have to test I lean out the idle mixture, and retard the timing. It's always worked for me. I imagine I wouldn't have to do that if the engine didn't have almost 200,000 miles on it.