250ce running rich

First off all, hi everyone and thanks for the add!
After bigger service made on the engine and car itself and checking a lot of components it still have following issues:

- Car is running rich, spark plugs gets black and clogged after a while, has big fuel consumption
-with cold start, engine has maybe 400-500rpm, and it is almost dying, when engine is hot rpm is 1200-1300rpm, while standing i P.
- some sort of lack of power.
-screw on the intake manifold for adjusting rpm does not seem to work
- with disconnected cold start valve car seems to run little bit better, so it is off for now
- engine runs rough and shaking

I'm writing down following things which I have checked in last few days:
+ Fuel pressure, exactly 2 bar pressure
+ MAP sensor(type 3 with black cover on), pumped 0.5 bar vacuum, it is standing there, no leakages
+ Ignition, been replaced to electronically, ignition point, 4* BTDC
+ AAV seems to work, it sucks air in when cold, and stops afterwards, but maybe not completely stops
+ Installed new timing chain, because of excessive stretch (was ~8 degrees off between camshaft and crankshaft), restored engine head, all new seals, adjusted valves.
I drove 45km another day, it runs but engine doesn't feels very happy

Any ideas where I should look next?

Hi unknown user,

it would be noce if u could introduce yourself shortly and also sign with your first name. We like to greet each other by their names here.

Regarding your problems:

+ MAP sensor(type 3 with black cover on), pumped 0.5 bar vacuum, it is standing there, no leakages
BINGO! A 250 CE never has a type 3 MAP sensor. It always has a type 2 MAP sensor. You have the wrong MAP sensor, no wonder your mixture is wrong.

+ Ignition, been replaced to electronically, ignition point, 4* BTDC
Why would one do that. All but very early 250 CEs have transitorized ignition. And what does 4* BTDC stand for?

I just wrote a long answer, but it didnt seem to appear here.. I will do it later again, then. I used quick reply button.
Regards
Lauris

Volker
4* BTDC = bevor top dead Center. 4 grad früh Zündung.
Rudiger

Long story short. I live in Norway, near Oslo and working at the Nissan/Subaru dealer as a car body worker, currently, for last year I am working at Tesla department as car body worker/ technician. Educated as mechanic as well. Passionate about Mercedes, I have had few before too.

Ok, back to the case.
The car is registrated in mid 72', but is a pre-facelift model, I believe it could be few years older. Car was designated for US market, but never were exported and was sold new in Norway. (I have orange side markers on rear on front fenders, on the steering column I have also riveted plate where gear shift mechanism should be, but have regular 4 gear automatic instead). Those who knows, asks if ti is a US import car. Could it be at US market 250ce cars has type 3 MAP sensors or it is only type 2? If so, where could I find one?

Ignition, well, I had hard times finding right parts for points, and have at least 2-3 wrong points, even if I ordered them from different places after car spec., I always got wrong ones, the same with ignition rotors. I ordered one for 114.980 engine which I have and still got wrong. (Most parts I am checking from w113 and w108/w109, like fuel filter fits from w108, but not the one which should be for mine.)
I got huge improvments how the engine works, when installed electronical ignition, so I will keep it until all the systems works properly, because ignition seems to be very stable now.
And 4* BTDC stands for - ignition point is set to 4 degrees before top dead center, like Rudiger allready mentioned it. I have transitorized ignition system, so I did included it when wiring up this electr. ignition.

Any other ideas or it is just to find type 2 MAP sensor in the beggining?

Regards
Lauris

Hi Lauris,

all 250 CE have type 2 MAP sensors. You will find component list in Appendix A . A type 3 is definitely wrong. I am pretty sure that your 250CE one day had a broken diaphragm and some smart ass replaced it by a 0280100111 for 280 engines. Buying a type 2 MAP sensor is a gamble as people mainly sell them when they are leaking. I will check whether I have suitable for you in my stock. I should have, but I have to search.

Also all ignition points including transistorized ignition module are in that Appendix A. A contact from Bosch with ignition module will not wear any more. I would BTW have understood 4° BTDC but you wrote 4* which I read as 4 times and got confused. I recommend that you also check what happened to your ignition module 0 227 051 015. Sounds like it also vanished.

Ok, thanks. I would appreciate if you could check your drawers for one working type 2 sensor But you think it would fix problem with rich mixture AND low/high idle rpm at the same time?

I am pretty sure I haven't seen any ignition control module here, but who knows.. Ignition distributor nr on mine is 0231 301 015.
I will attach few pictures from engine compartment, so you can see what we are dealing with.
Lauris

Hi Lauris,

I will check over Easter and I will sure find one for you. The one that is mounted in your car is the type 3 MAP sensor for 280 engine as I can see from white E label. You also have pre-resistors for a transistorized ignition. Your ignition coil was once replaced with a newer one. Please check that it is 0 221 122 001 . I cannot see your ignition module but I am also not too sure where it is located in your car.

Correct MAP sensor will not help to fix idle-rpm problems. Please check your AAV (auxiliary air valve) and vacuum leaks. Please also verify that you have correct ECU plus green injectors which must not leak fuel.

Hi, Volker,
and thanks for reply.
Ignition coil is from BOSCH, but stickers are off, so no part numbers visible, but right now it is mounted aftermarket coil, it is BERU ZS565. But the ignition seems to work fine.
About injectors, I got restored injectors, they are the same part number, but yellow tips, not orange ones, which are replaced with yellow one now and are mounted in the car. See attached picture.
I found one map sensor locally, but it is for 280se 4.5l with part nr bosh 0280100100, but it problably wont be the right one? PS. I found in appendix, that map sensor is for 4.5l engines.

Happy Easter!

Hi Lauris,

yellow injectors are definitely wrong. You need green ones (like 0280150035). I can check whether we can swap them. Your coil ZS 565: I cannot find any data of that. You should have ZS400 or better Bosch 0221 122 001 for transistor ignition. You ignition module should be connected to a wire between both reisistors. Please follow those wires and read

jetronic.org/de/107sl-wsm/107sl-wsm-cont...-107sl-ri-engc-m116D chapter 07.5-519 page 3 and ...520 . There you see the ignition module and wiring scheme.

Some "specialist" really changed everything on your car.

Hi Lauris,

after searching all my drawers, I found the right MAP sensor. Will have to verify it now over Easter as it is a used one. And if it is not ok, I know someone who can fix it

Hi Lauris,

please read the Bosch no. 0 280 150 xxx on your injectors on the plastic mould. Yellow injectors have less flow than the green ones. Sometimes some smart asses use L-Jetronic injectors as a replacement which does not work at all. And to complete read ECU and throttle switch no as well. Then it is complete.

Hi Lauris,

Christian found where your ignition moduel is located: It is underneath your battery:

Hi,

regarding your idle-run problems. On your pictures I see that the banjo bolt on the intake manifold is open with a hose closed by a screw. That might well create false air and varying rpm.

Hi, injector no. is 0 280 150 035. Idle-rpm is stable high when engine is warm, f.eks but if I remove one vaccum hose, so it gets even higher. That hose with the screw on goes to rear seats, so I closed it and checked, because rear seat realease button doesnt work. rpm are really high, so it has to be a major issue in vaccum system then. When engine head was off, so I went over gaskets and changed most of them or made new liqued gaskets for intake. And I refitted all of the clamps and fasteners. It has to be in order I think. When I checked engine vacuum on one of the hoses, so it measures good enaugh I think. I attached picture. But I would like start with the right MAP sensor and need to check AAV as well. I was bit short of time because in Easter arrived w123 230ce at home, which is a side project for the moment.

Lauris

Hi Lars,

MAP sensor is here. Please check your AAV. I have both 0 280 100 006 and 0 280 100 025. I recommend to use 0 280 100 025, but both are valid for 250 CE. Unscrew micro filter and check on warm engine whether it sucks in air there.

Ok, that's good news! Are you interested to exchange it with mine or want to sell it? I did vacuum tested it and it holds vacuum good. I have dissambled some parts right now, so it is not quite drivable, but I can see if I can get it to warm up tomorrow and get ckecked that AAV.

Lauris

Hi Lauris,

you can have that MAP sensor. But please check AAV first.

Hi. Some latest updates. Pictures included.
AAV with filter off - sucks air in quite hard at the beggining when engine is cold, when engine temp gets up, idle rpm gets up as well. After 5-10min engine reaches 80° and aav still sucks air in, engine just revs and cannot hear the valve so well, but it feels like about the same when engine was cold, like still sucks air in quite hard. When I block the intake hole for aav, engine stops right away.
PS. Is this the right aav, as it looks different then others I have seen? (First picture)

Throttle body - No idle rpm changes with or without contact off. When adjusting throtlle valve min to max with the screw on the side, rpm drops for 2 seconds and goes back to high again. I have adjusted throttle valve like it almost sticks when closed, but it not sticks, I think it should be ok. But does it even works?

MAP sensor number on mine - 0 280 100 111

Any new ideas?

Regards
Lauris

Hi Lauris,

this is the right AAV. Should be overhauled and should have a new micro filter.