Solex PAITA carb

[NutmegCT]

Sorry for the delay. For some reason I no longer get email notice of replies to any threads. Weird.

I'm getting a replacement for that mixing tube. Hopefully today or Friday.

Puzzling thing is, the mixing tube has nothing to do with starting the car. It only comes in to play when the throttle is held open.

To start the cold engine in temps above 50F: pop gas pedal once, release. Ignition on, hit starter button.

Manifold vacuum is *supposed* to suck gas from a small hole just under the primary butterfly. This doesn't seem to be happening, or at least I see no evidence of it.

Only way to get the car to start is to constantly pump the gas pedal (which constantly squirts gas from the accelerator jet above the butterfly, down into the throat).

Strong spark, strong fuel flow, bowl full, timing set, coil good, all butterflies close and open freely as designed.

Weird #2: open primary throat, drizzle gas into manifold, close butterfly, crank starter. Nothing. Only way to gt it to fire is constantly pumping gas (accelerator jet squirts).

grumble grumble

Tom

 

[Opa]

Tom sounds to me that there is some blockage in there somewhere after the main jet?View attachment 24468

 

[NutmegCT]

yep - I hear ya. Sure seems there's a blockage. But trying to find and clear it is proving a challenge. That 33 in your diagram looks very much like the 32 I have. Note the idling spray in the Idling diagram on the right. That's the flow I think I'm missing.

Thanks.
Tom

 

[Opa]

Tom, if your emulsion tube was plugged #65B in attached diagram was gummed up, I would also check the passage way between main jet#68A and #68 for blockage. Also check the choke disc for orientation. IIRC this can be installed a half turn off? thus not opening proper holes? Been a long time since I had anything to do with a Solex 32 PView attachment 24469aita

 

[NutmegCT]

Thanks Casey. I remember both 65a and 65b being clear. Question for you: if I don't use the choke, and don't touch the throttle linkage, shouldn't the engine fire just from the gas coming from the idle jet port?

Edit: I"ve checked the choke setup twice. The rotary is in the correct orientation.

Manifold vacuum sucks air down primary throat, and sucks gas from idle jet. Both passages are open. Shouldn't that be enough to fire and run - eliminating at least the secondary throat from the equation?

Tom

 

[NutmegCT]

PS - I just tried blowing air from the port at #68a to #68. No air comes through. My eyes ain't what they used to be. Where on your chart would I see that passageway?

Tom

 

[Opa]

Far right pic shows idle circut fuel flow(indicated in black)from emulsion tube to idle jet below throttle plateView attachment 24471. emulsion tube should have a jet in it and it may have a small air jet along side of it. Google mbzponton.org pictures there may be easier to decipher.

 

[NutmegCT]

Thanks. I actually got many tech documents from MBZponton. I agree that the right-most picture shows the connection from the emulsion tube to the idle mixture jet. But didn't you say something about "check the passage way between main jet#68A and #68 for blockage."

Far as I can tell, 68a leads to the fuel bowl, and 68 leads to the fuel bowl. Both of those passages are clear - but not directly connected. Thus I can't find the passage between 68A and 68 you mention.

By the way, I really appreciate your suggestions.

Tom

 

[NutmegCT]

Hoping to keep the suggestions coming!

While I've got the carb out, I also removed the spark plugs (new NGK, correct for this car). Decided to check cylinder compression.

Cold engine, throttle open (no carb), five seconds cranking: 160, 160, 162, 160 psi.

The M-B workshop manual says to expect between 128-146 psi.

Is this a clue? Still seems to me that with a good spark and timing set, gas dropped into the manifold should ignite. But I'm grasping at straws here!

Thanks.
Tom

 

[Opa]

Tom,compression numbers look good,you say you have spark, so at the rate all it needs is fuel, which may require a dissassembly of the carb and a good cleaning of all the little passages.
If you still have the card off the manifold, put your hand over the intake holes and get someone to turn the engine over to make sure it's got good vacuum, if not,you may have a gasket problem.
Pouring fuel into the carb can sometimes take a few turns of the starter to get the fuel into the combustion chamber, depending on style of manifold, length of runners etc.
Does your manifold look like this?

 

[NutmegCT]

Thanks Casey. I figured the compression looked good, but just wanted to make sure.

As I mentioned earlier, I took the carb off several days ago, soaked it, cleaned all the passages and jets, installed new idle mixture jet and fuel bowl needle, etc. Put it back on, no improvement. The big thing I'm waiting for is a replacement emulsion (mixing) tube for the primary throat; should arrive Saturday or Monday. Mine had been "repaired" years ago (top of holder was broken off and tinned back on), and had the incorrect size jet (160 instead of 180). I'm hoping that's the culprit, but seems the car should at least fire and idle even if that mixing tube was totally bogus.

Here's the manifold - picture from a few minutes ago. I'll ask my neighbor to help me with that manifold vacuum check this weekend.

I have to keep in mind that the engine ran fine two weeks ago before I bought the car. I drove the car off the delivery truck ten days ago. Since then, the starting/running problem has continually deteriorated.

Thanks again for hanging in there with me.
Tom

View attachment 24497

 

[Opa]

Tom, The main jet,emulsion tube and air corrector all must hold hands in order for the main circuit to act as it should. Likely when you get the new pieces this will be proven.(i hope)
I studied it a bit more, and would think it should run on the start circuit as it looks to me that is a curcuit all it's own.Fiqure 1 on the left side shows ST3 top right which is called starter air valve which looks like an emulsifier for the cold start circuit, see arrow just left of the number 6 behind float bowl which then shows fuel blended with air going to starter valve marked st 1 Hopes this makes some sorta sense

 

[NutmegCT]

Casey - that's what puzzles me too. If I use full choke, I still get no firing.

As of two days ago, the only way to get the engine to fire, is to crank it while pumping the pedal - which squirts gas from accelerator jet into primary throat. Stop pumping pedal, engine stops firing. Last week at least I could get the engine to idle, by drizzling gas into the primary and cranking. Eventually it would catch and then settle into a smooth idle - but then just die out after a minute or two.

Say, any idea how that "starter air valve" St3 works? I replaced the gasket when I rebuilt the carb. I can hear the valve pop open/closed when I push against the plate that shows on the underside of the carb top.

PS - we did the vacuum test. Crank engine, hand over manifold ports - strong pull of air.

Tom

 

[PAUL161]

Tom, I've been following this problem and good advice is been given, but, I have one question, to your knowledge, has this engine been apart, has it had a new timing gear/chain? Does it spit back? I could be way out in left field but it sounds like the cam timing could be off somewhat. PJ

 

[NutmegCT]

Thanks Paul. Timing chain and tensioner were replaced about 20 years ago. I've actually got many maintenance records going back to the 1970s.

No spitting or backfires. Valves set correctly. Timing set correctly. Distributor set correctly with new points and wires. New plugs.

Three weeks ago I started it before I bought it. Day of delivery, I started it and backed it down from the truck. Once it became mine, it's been a dismal downward spiral.

Reminds me of my high school dates.

Tom

 

[waltesefalcon]

Crazy question, but do ya'll have mud daubers up there?

 

[NutmegCT]

Mud daubers no - paper wasps yes. But no trace in the car.

Not even in the air cleaner - which isn't installed. Previous owner got a bit careless while doing maintenance, put the canister on the garage floor, had lunch, and then backed over it. Not a pretty sight!

View attachment 24558

 

[waltesefalcon]

So timing is good, fuel flow to carb is good, vacuum is good, spark is good, no obstructions in intake, valve timing is good. Do you by any chance have a spare carb sitting around? Kinda grasping at straws here. You could probably tell that by the mud dauber question though.

 

[NutmegCT]

Thanks. A friend has another 190b like mine, so if the new mixing tube doesn't fix the problem, I can take my carb to his car and see what happens.

Just tried a last ditch test. Carb is off car. I poured about two tablespoons of gasoline directly into the intake manifold. Cranked it about ten seconds. Didn't fire once.

Should it have fired? Or maybe the air/fuel mixture wasn't correct, because of no carb being there.

If it fired, it would tend to indicate the carb is the problem. But since it didn't fire at all without the carb, I wonder if that points to something "more basic".

Gol dern it ... I drove it off the shipping truck for pete's sake!

Tom

 

[waltesefalcon]

It should start. Just putting some gas down it might not work as well as using an atomizer of some kind for your gas or just using an aerosol can of starting fluid. I have started many a car with no carb on them by shooting some carb cleaner or starting fluid down the throat.