TheSamba.com :: View topic - FIXED?!?!?! 1974 SB solex 34 pict 3 stalls when warm (video)

Thu Nov 14, 2019 6:18 pm

Hi guys. My beetle has a solex 34 pict 3 and I’m having issues with it idling when warm.

The car starts beautifully but once it begins to warm up and the fast idle screw is sitting on the second from the last step on the cam, it stalls. It’ll run just fine however if I pull the electricity to the choke as the butterfly isn’t opening. If I manually open the butterfly it’ll stall as well.

The carb has been taken off and cleaned (obviously jets as well) I’ve checked the throttle shaft for vacuum leak, i replaced the choke coil element.

Here are 3 videos. You’ll hear a little ‘hiss’ if you turn the volume up.

Thank you in advance for any advice. Also, I’m sorry the videos aren’t on The Samba. I will upload them from my PC as i keep getting a ‘corrupted file’ Message when I try to upload it from my phone.

stalling while warming up:

https://imgur.com/a/lZagFiM

running after pulling 12 v from choke:

https://imgur.com/a/lZagFiM

Manually opening butterfly (which also causes it to stall):

https://imgur.com/a/RfrOQS3

Thu Nov 14, 2019 9:24 pm

Do you want me to tell you what to do to stop the stalling, or do you want me to walk you through how to discover it on your own? :P

Robbie

Thu Nov 14, 2019 11:37 pm

asiab3 wrote: Do you want me to tell you what to do to stop the stalling, or do you want me to walk you through how to discover it on your own? :P

Robbie

I do. Part of the reason I’m on this forum. Always looking to improve my sorry skills. I read stuff here that doesn’t pertain to me just so I have an idea when/if stuff should happen.

Fri Nov 15, 2019 12:03 am

Ok, for you, Xevin…

Long ago, carburetors used to be these strange devices, which were often called funny names like "Solex" or "Stromburg." They were mischievous little doodads which did nothing other than sprinkle a little fuel into some flowing air. If you can remember this, you can master your single carburetor quite quickly; no need to be an old grumpy dude in a dirty shop with your name embroidered on your coveralls.

Cut to the late sixties: For some reason or another, (people liked breathing air!) as cars became more popular, carburetors had to clean up their act. The "pict3" carburetors did this quite well at idle, by giving us more precise idle control with a speed and mixture screw set on the left side of the carb. This allows us to alter the sprinkling of fuel in ratio (small brass screw) AND in volume/speed (big brass screw.)

Knowing that, you, the Mechanic In Charge, can now "ask" the engine what it wants by simply turning those two screws in calculated directions. The screws act as "faucet handles," so loosening the screws will allow more fuel/speed, while tightening the screws will allow less fuel/speed. Remember, a "richer" mixture has too much fuel, and a "leaner" mixture has too much air. At idle we want to be right in between. [Chemists call this "stoichiometric," or about 14.7 molecules of oxygen for every molecule of gasoline. Not that we're nit-picky here on TheSamba. :ts: ]

Try it. Turn them both out exactly one turn. See what happens. Hell, try two turns. You can ALWAYS revert back to your old settings if you don't like it. And it's free. Having fun yet? :lol:

The other way you can talk to your carburetor is by placing your hand over the open throat like Mr. Spock, and gradually close your fingers together to "choke" off the carb. If the engine sounds peppier, your mixture is LEAN, and you need to add fuel to correct it. If the engine bogs down worse even before you have completely closed off the air flow, you are probably too rich. Once you can tune a carb by feel like this, you will have earned your own greasy shop coveralls with your name on the label.

After asked your engine what it wants, gradually use the screws to adjust your engine to it's happiest place. Get the speed in the ballpark, then get the mixture to where the engine is running fastest. Then readjust the speed if you have to, then get the mixture to it's happiest, right before it drops off if you screw in too far lean. I hope you like herding cats.

Looking at the choke plate in action, you've already witnessed that the engine runs better when airflow is blocked. That's literally the choke's job. Choke off the air. Nice work, choke, keep it up. It seems the engine wants to be richer. You didn't even have to ask the engine about that, it was chatty and all you had to do was listen! :lol: Most of the "tests" I use above only work once the choke is mostly open. With a fully-engaged choke, the mixture is usually too rich to be diagnostically useful.

Now, why would an engine start acting up when the choke allows the rich mixture to become lean??

Robbie, but my coveralls say Bob

Fri Nov 15, 2019 11:49 am

Whoa!!!! That was quite the reply. Lol. Thank you for taking the time to do that. I’ve attached a video of the car RUNNING.

Now I’ll actually be able to get the air cleaner on and adjust the mixture. For what it’s worth - the bypass screw is now set at 1.5 turns out from bottom and the volume is 3 turns out.

I also found the ‘Mr. Spock’ method helpful so cheers again for that!

Here’s where it’s at this morning:

https://imgur.com/a/5fOkWeo

Fri Nov 15, 2019 8:36 pm

Here is a great video on these carbs.

https://www.youtube.com/watch?v=3MVdscVjEn8

Sat Nov 16, 2019 8:10 pm

Diggin the chic working on her super beetle, rock on! =D> Good luck with your issue!

Sun Nov 17, 2019 10:13 am

rayjay wrote: Here is a great video on these carbs.

https://www.youtube.com/watch?v=3MVdscVjEn8

Thank you! I watched it and ‘bookmarked it’ 😀

Sun Nov 17, 2019 10:16 am

cajun_sun_bug wrote: Diggin the chic working on her super beetle, rock on! =D> Good luck with your issue!

Haha. Thanks. The car is running well today. We’ll see what happens tomorrow 🤣

Mon Nov 18, 2019 12:04 am

asiab3 wrote: Now, why would an engine start acting up when the choke allows the rich mixture to become lean??

I asked this because it's diagnostically relevant! I'll still give ya a day or so to think about, but don't think you're totally out of the woods just yet…

Robbie

Mon Nov 18, 2019 12:51 am

newtosamba wrote: cajun_sun_bug wrote: Diggin the chic working on her super beetle, rock on! =D> Good luck with your issue!

Haha. Thanks. The car is running well today. We’ll see what happens tomorrow 🤣

Damn it! I watched those videos looking for a chick working on a SB. All I saw was some man hands that probably play guitar :wink: Or roll 12 sided dice :lol:

What’s the riddle asiab3?

Mon Nov 18, 2019 4:38 am

Vacuum leaks ?

Mon Nov 18, 2019 5:48 am

Based on your videos, the engine wants a little bit richer mixture. If you're satisfied that the carburetor is clean inside and there are no vacuum leaks, try backing out (turn left) the small mixture screw about 1/4 turn at a time and trying it over a couple of days between adjustments. You can adjust the larger air bypass screw later.

This assumes that your ignition and valves are adjusted properly and your heat riser pipe is heating up the intake manifold quickly on a cold engine. Your engine actually sounds pretty good except for the lean stumbling. All carburetors "hiss" when listening down the throat, but double check really well for other vacuum leaks.