28-PICT suddenly won't idle and leaks fuel

[pdb27]

My ride is a 65 bug with 1385 40-hp motor, which runs like a peach with an old German 28-PICT carb and not great with a new EMPI 30-PICT carb. I prefer to run the old carb, but last fall it quite suddenly quit idling ... meaning one stop sign it was great, next stop sign NO IDLE. It still started, accelerated, and drove like always. After returning home I also noticed a sizeable fuel leak that covered the left side of the carb.

So, I finished out 2023 with the EMPI carb and rebuilt the Solex over winter. I thought I saw a crack in the body near a casting seam in front, which I covered up with JB Weld as an experiment. Everything else looked great, including the jets, which flowed great with carburetor cleaner shooting through.

This spring I ran the crappy EMPI once or twice before putting on the SOLEX. At first, the SOLEX seemed its old self, including no fuel leaking, but now it no longer idles and is starting to drip a bit of fuel. After reading through the posts, I couldn't find anything that was similar to this sudden failure mode. I DID find a post about opening up the vacuum ports on the EMPI, which I might try ... but I'd much rather continue to run the old German carb. Any ideas on what is ailing it?

[Eric&Barb]

Check that the shut off float has not gotten fuel in it.
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[pdb27]

[Eric&Barb]

[bnam]

Check the needle valve.
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1971 1302LS Convertible (RHD) owned since '74
Click to view image
1965 Karmann Ghia Coupe - under restoration
1966 Fiat 1500 Cabrio (with 1600 Twin cam)
1952 Citroen TA 11BL

[zerotofifty]

[matthew henricks]

X2 on the float valve. I rebuilt my 28 PICT and had all sorts of trouble traced back to the repro float valve. I cleaned out my old valve and all was well.

You can also check the angle of contact to the float. If it gets bent it may not engage in at the right time.
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1964 Original Owner build Thread. https://www.thesamba.com/vw/forum/viewtopic.php?t=702135&highlight=

Ambulance Fan's. https://www.thesamba.com/vw/forum/viewtopic.php?t=627707&highlight=

Parts i am looking for:
64 bug nice used front/rear Black LHD floor mat.

[pdb27]

[Eric&Barb]

White exhaust smoke is water vapor on colder days condensing. Burn fuel with oxygen = water in the exhaust. Hydrocarbons are made up of carbon and hydrogen which in essence you tear apart by burning. Which is why it is best to run the engine for long enough time to heat the muffler up to dry out the inside of it to keep it from rusting out from the inside much sooner. EG if we have a bunch of errands to do, we drive to closest one and work out to the farthest stop, then back home to get longest run before shut down.

White tinged with blue is oil burning.

Black is too much fuel.

Choke on with too much fuel might explain cold startup problem, but not persistent with hot and cold engine conditions since choke should be off when the engine is hot. Still would not hurt to check choke function....

It would help to know where on the left side of the carb is the leak coming out.

Could be you just have a leak at the top gasket of the carb left side and a clogged up idle passage.
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[pdb27]

Update: Pulled apart carb, cleaned thoroughly with carb spray, soaked the parts in carb cleaner, cleaned with spray again, put in new rebuild kit. Put in OG fuel shutoff valve that worked freely, swapped in another OG float that passed the boiling water test. Bolted on, ran up and down the road ... and still leaking.

The leak was first noticeable near the main jet, which checked out OK for tightness. It's actually dripping underneath the carb body near the jet and running downhill to the brass hex.

After a few minutes I can see fuel dripping from where the throttle cable is attached, and not long after that I can see it dripping from the other side of that shaft. Top of the carb is bone dry, so the fuel shutoff valve seems to be doing its thing.

At least it idles a touch better now, and it still runs up and down the road great; it puts the EMPI carb to shame. Any new thoughts?

[Eric&Barb]

Crack in the carb body?

How are the main jet plug to body sealing surfaces, scratched or corroded? Needs to be smooth, flat to seal with the gasket.

Maybe the main jet plug itself has a pin hole, switch to see if it still leaks.
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[pdb27]

Time to put a cherry on top of this one: it has to be a crack in the body. I rebuilt the carb again, cleaned it in the carb soaker again, tested for leaks past the main jet, and reinstalled with fresh intake manifold gaskets. Still wouldn't idle, had a new flat spot at low RPMs, died 3 times, and leaked fuel from everywhere. With the air cleaner off I could hear bubbling inside the carb, even though everything was cool to the touch.

A developing internal crack is the only scenario that seems to match all the symptoms: sudden failure to idle, worsening leaks, trouble at low RPMS, and getting starved of fuel at low speeds.

Thanks to all commenters.

[Eric&Barb]

FYI the rear mounting stud in that carb should have its upper end just above the flange of the carb body. I know it is probably a moot point if that carb has a crack, but for future if that stud is not all the way thru the carb threads it has a much greater chance of having the female threads pull out due to that much less threads being engaged by the stud.
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[pdb27]

[Eric&Barb]

Funny how that happens!

Hopefully you can pickup a good used original carb at a VW swap meet near you soon.
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