Pierburg 2B4 Carb fuel mixture adjustment

[demos]

Hi, I bought a 1981 316 M10B18 with a Pierburg Zenith 2B4 carb with automatic choke.
Car is running very rich. Black smoke from exhaust, engine oil so black it looks like diesel engine soot. I noticed vacuum lines were messed up so I replaced and re-ordered them.

Where's the fuel mixture screw on this carb and what are the recommended number of turns to get rid of this black smoke?
How many turns should I turn the AIR FLOW-SETTING SCREW 13111265993, number 19 in this graph:
https://www.realoem.com/bmw/enUS/showpa ... Id=13_0067
Or is it item number 22 in previous graph?

How can I test the thermo actuator if it's working or not? It's p/n 13111705874 (item number 3 in realoem graph)

There's slight fuel leakage from the upper gasket, nothing serious, if you put your finger on the gasket you'll get a trace of fuel shaped like a thin line.

Choke is working fine, it's closed when car's cold and opens when warm.
I replaced the piston p/n 13111705875 with a new one.

[Peter V.]

Hey,

Welcome and please introduce yourself. Your answer can be found on the forum.

https://www.bmwe21.net/forum/viewtopic.php?t=23486

[demos]

Thank you Peter. I've seen ruddies site and used Google translate, that's how I fixed the vacuum line orientation. However I don't see where it says how many turns to adjust screw number 19, part number 13111287847. And screw number 22, part number 13111276935 in realoem graph.

The car I purchased had been parked for many years (over 10). At some point someone cancelled the mechanical fuel pump and installed an electric one, but they didn't put a fuel filter. Just today I installed a MANN WK613 compatible filter, and already the black smoke has severely decreased.

I used a can of AC Delco Carburator Tune-Up like this one:
https://www.amazon.ae/ACDelco-Carburato ... B07MMK33DC

Before the filter and carb clean, the car used to shake when passing the 3000rpm, and barely reached 4500rpm. Now it's running smooth all the way to 5500rpm, but once it reaches 5500rpm the engine power drops suddenly and engine brakes as if I down shifted 2 gears.
I think the M10B18 should rev all the way to 6400rpm. So I don't know if this happens due to carb. issue or electrical issue (Spark Plugs are brand new, so it could be dizzy or ignition coil if it's electrical). Any hints guys? I'd really like to rev it to 6400 or even 6k.

I took her for a drive, reached 155km/hr. After driving for about 30km, carb started to shoot fuel and engine dies unless I rev it to say 2000rpm.
Here's a video that shows what happens:


When the car cools down it behaves normal again. Any hints here?

Last question, my car has a 5 speed gearbox. When I engage the 5th gear it slows down and revs higher, it's as if I went from 4th to 3rd gear instead of going to a higher 5th gear. Is this normal? I'll read any numbers on the transmission and post them.

[demos]

Quick update: Ignition timing was off, fixed that. Replaced ignition wires and distributor cap. Also managed to get full repair kit from Germany, comes with 2 gaskets, the diaphragm, lots of plastics (useless cuz the original ones are fine on 3 carbs that I've seen, I changed them cuz they were colored white the old ones tend to go brown/yellowish) but it has the nice blue plastic cap for the throttle screw. Floats and needles were fine but since I got them from the kit, I replaced them. I wish the kit came with Jets instead of the plastics. Also did valve clearance adjustment, found 4 or 5 valves were too tight. Car has only 63,000km I think they've never been adjusted for the last 10+ years.
Replaced electric pump with original mechanic one.
I had installed a brand new bmw p/n: 13111287844 I believe you guys call it a "TN-starter" I've read elsewhere it's called TM-Starter, and in BMW etk it's called a "actuator"...anyway the brand new one I got seemed to be out of spec. At 20c degrees it didn't extend at all, it should extend to push the piston in carb so that the gap would be about 4-6mm. So I got another brand new one, and now cold starts have much less black smoke.

Engine no longer dies after a long trip. And no more gasoline sneeze from carb. But engine's still running a bit rich. The idle screw has very little effect on the richness, also the CO screw if any effect at all. I don't have a CO analyzer, but my eyes see trace of BLACK smoke, and my nose smells gasoline.
Plus, car has a slight stutter/hesitation when going from 2500 to 3000rpm and then smooths out, and going above 4000rpm. But black smoke and the stutters are very slight/light compared to before. I bought a new airflow valve p/n: 13111705874 but it still hasn't arrived, although I believe the one installed is already working.

Is there any place to buy all sets of proper jets for this carb ? I'm thinking of replacing all jets for peace of mind and hopefully getting a smooth power delivery along the RPM range.

Couple of pix:

[demos]

Forgot to mention, first thing I noticed earlier that brake servo was damaged leaking alot of vacuum after long drives. If I kept holding brakes down the idle would stablize, once I released my foot off brakes engine would slowly decrease rpms till it dies or barely holds 400rpm. Replaced that before I did anything. Then replaced the master cylinder which was leaking, and I think that's what damaged my servo. Then I went on adjusting ignition timing.

[Jeroen]

Not aspecialist here, but the inside of the head is pretty clean! Judging the old style bolts used it could very well be that the head has never been off the engine in all these years!

[demos]

Car had 62,500 kilometers, I drove it about 500 kms then the odometer stopped working. I think a plastic gear broke/popped.

I have an S54 E46, and an S85 M5, an E30 M20B20 320i, I've never wanted to own an E21 but when I saw this car, 1 owner, and its condition, I had to buy it. The interior is like it just left the factory too.

[Jeroen]

Can imagine the car caught your attention, even though you have some great other cars in your collection!

[nic65]

my brake booster was also opened, serviced and closed because it had rust inside and I had braking and idling problems