Solex 32 primary dripping fuel

[johnbrady]

I rebuilt the twin Solex 32 PAITA carburetors on my 59 220S and there is fuel dripping from the primaries. The accelerator pumps were leaking fuel when I bought it, which prompted the rebuild, so I don't know if was a preexisting condition. I checked the float levels and even set one on the low side. All of my searches have only found the float as the suspect. Did I miss something in the rebuild? Any help on where to look would be appreciated. Thanks.

[joshhol]

I'm not an expert but a couple guesses come to mind:

1. Throttle linkages
2. Heat risers stuck open causes heat to bubble fuel over
3. Fuel return valve. I may not be describing this right but worth a shot. Normally it lets fuel return to the tank but that spring level closes the circuit when you are hauling arse so the car doesn't fuel starve itself.
4. Lastly, how did you adjust the float level?

[johnbrady]

The throttle linkage is all the way off. I can't calm the idle down because it is getting too much fuel from the primaries. but I have to have some idle adjust on each carb to keep it running. It will run at an elevated idle or not at all.
It does it all the time; cold or warm.
There is no fuel return on this twin carb system.
I adjusted the float level by running the engine, opening the carb and measuring the level from the fuel to the top of the float chamber. Rebuild documentation on mbzponton.org says 19 to 21 mm. I put one at ~23mm and still didn't fix it.

[joshhol]

Getting beyond my expertise but the only other thing I can think is the rotary starter air valves could be 180 out. Not sure that would cause the problems you are having.
I did a post about positioning them not too long ago.

[johnbrady]

I checked the air valves. They are in correctly.

[gmog220d]

Where exactly is the extra fuel coming into the carbs? From the the discharge holes in the primary emulsion tube holders?

After removing the emulsion tubes from the holders did you find a little plastic ball underneath, down in the emulsion tube holders? Not sure what it's for, this little ball. Perhaps you're missing them? The ball I am talking about is part #63a in this diagram, top left corner:

http://www.mbzponton.org/valueadded/maintenance/carbrebuild/solex_type_32_paita.jpg

I too would think the fuel level is too high, but you checked that.

RE: Having to turn up idle speed to keep it running. Almost seems like you have a different problem here, something not right with the idle circuit (blocked passage, plugged jet). A carb with a blocked idle circuit won't idle, but it'll "idle" on the mains if RPMs are high enough. How many turns out from all the way in did you pre-set the idle mixture screws? Could they be in too far?

[gmog220d]

One other question: Did the engine idle more or less properly before you rebuilt the carbs?

[johnbrady]

Yes, the fuel is coming from the discharge holes in the primary emulsion tube holder. It seems to be 'spitting' rather than 'spraying'. There is no ball below the emulsion tube. The tube is sealed at the bottom. I attached a picture. There was no ball in either carb or in the 'parts carb' that I have. The rebuild document on mbzponton.org also mentions finding no ball.

Mercedes-Benz Ponton Solex Type 32 PAITA Carburetor Reconditioning © www.mbzponton.org

I started with the idle mixture screws at 2 turns and I had them out to just over 3 turns and no difference.
The car would not idle well before the rebuild. It hadn't run in over 3 years. I could get it to run with the choke and both carbs were leaking fuel from the accelerator pumps.
I think the issue is the 'spitting' of fuel from the primary discharge is causing it to run too rich and uncontrolled. But I don't know what is causing it. I lowered the fuel level and it didn't fix it.

[gmog220d]

I too looked at that page. That's where I found the exploded diagram I linked to above.

Here's item #4 quoted from the Disassembly part of the write-up (bolds mine):

"My "Glenn's Repair and Tune-Up Guide" refers to a little ball in the primary emulsion tube, under the jet. Both my carbs had no little balls. They did however have brazed semi-circular ends to these jets. I think there has been a design change here since I carefully measured the clearance between the jet and tube and there is no chance of an extra ball fitting inside this emulsion tube. Jack and others also do not mention little balls!"

So he was looking for the ball to be between the jet and the top of the emulsion tube. According to the diagram and the instructions in the Glenn's book the ball would be below the emulsion tube, not on top of it directly under the jet. So one would have to remove the air corrector jet (#65a) and the emulsion tube (#64) to get at the little ball (#63a). The write-up doesn't specify if this was done or not. Indeed, in the pic labeled "Carb disassembled and cleaned up" you can see that there are still jets installed in the top of the carb body, including the air corrector jet in the top of the emulsion tube holder. Maybe the pic was taken after partial assembly. Maybe not . . .

Basically, I trust the diagram and the Glenn's book more than I trust a rather incomplete write-up. If were in your shoes I'd want to know for myself.

After more thought seeing fuel spurting into the venturi from the discharge ports in the emulsion tube holder, especially at higher RPMs, could be normal. After all, those holes are where the fuel going into the engine comes from. I've seen fuel dripping from discharge ports with the engine running on other carbs I've worked on, engines that were running just fine. You might simply have a problem with the idle circuits not working as they should, hence the engine only running at higher RPMs (i.e. running on the main circuits only).

2 - 3 turns out from bottom sounds like a good starting point for the idle mixture screws. Try turning them all the way in to intentionally lean out the idle mixture to the point the engine will be starved at idle. Does that make the situation worse, or does it remain the same? If it makes no difference I would suspect a problem with idle circuits even more.

BTW: Did you ever get this issue sorted out?

http://www.peachparts.com/shopforum/vintage-mercedes/377687-solex-type-32-air-correction-jet-65a.html

I suggest picking up a copy of the Glenn's book for yourself. They're inexpensive and plentiful on eBarf. Lots of good information on these carbs in there, info that was sourced from Mercedes-Benz.

[97 SL320]

A carburetor has 2 basic circuits, idle and main.

A few things.:

A high float setting , sinking float or high fuel pressure will give you a high liquid fuel level and rich mixture. At this point, fuel will be higher than the venturi discharge nozzle and you will have fuel drizzle. Fuel level should be some small distance below the discharge nozzle.

The idle circuit is like a mini carburetor that can deal with very low air flow. This mini carb is active when the throttle blades are nearly closed. Look for a slot and small holes near the edge of the throttle blade.

If the fuel section of the idle circuit is clogged, you will have a lean mixture and need to open the throttle blades to get the main circuit into operation. The problem is there isn't enough air flow to make the main circuit function properly and you will have a ragged idle.

A large vacuum leak will cause this effect also.

[johnbrady]

gmod220d, you are correct about the ball. I found it on my 'parts carb'. I was able to put a fine wire into the passage from the main jet and get it to move. I tried to blow it out with carb cleaner but it gets stuck at the discharge ports. Anyway, it's there and it's now free. I'll check them out on the other carbs when I get them off the car.
I think that you and 97 SL320 are correct that the idle circuit is not working and the primaries are the only way that the engine is getting fuel. I will pull the carbs and make sure that all of the idle passages are clear.

[gmog220d]

Good deal! Glad you took the time to investigate. I don't know that those little balls do, but they're there for a reason, and it's a good idea to make sure they are free to move like they should.

As for the idle circuit, a good starting point would be to pull the idle jets and take a look at the calibrated orifice in the tips. It may look clear to the naked eye, but under magnification you'll get a much better view. Even a simple magnifying glass is a good way to make this inspection. The tiniest spec of dirt or old varnished gas can plug them up and render the idle circuit dead.

[gmog220d]

Oh, and if you do find the orifice blocked in one or both idle jets try a blast of cleaner or compressed air directed right at the orifice to clear them. If that fails you can use a tooth pic sharpened to a super fine point to insert into the orifice and clear it, taking care to not break the pointed tip of the pic off in the hole. Do not use a steel/metal object for this as you would risk deforming/enlarging the orifice and throwing off the calibration.

[97 SL320]

The idle jets might be accessible from outside the carb, look at a diagram. Some carbs ( in general not MB specific ) have a second jet between the transition slot / idle mixture screw but I've only seen this on emission controlled carbs to limit how rich the manual adjustment can be made.

I've rebuilt hundreds of carbs over the years, with some care a braided cable strand can be used to poke out a jet. ( I save old throttle, transmission kick down or other small dia cables and unwind a single strand. )

You just don't want to use something that is as large or larger than the jet drilling otherwise the calibration can be affected. If all you have are pin drills, use the smooth end and never the drill point as the sides of the drill will change jet calibration.

[gmog220d]

The idle jet on most Solex carbs is easy to get to. They usually have a 8mm head. I'm attaching a pic from the Glenn's book.