Model idle CO difference??

[mulrik]

Hi there
Looked in my Haynes manual yesterday and it said that the CO level at idle is suppose to be 1,5 - 3% for a 250 SL (and 250 SE) while it should be 3,5 - 4,5% for the 280. Is Haynes right or should all pagodas have the 3,5 - 4,5% CO level at 800 RPM idle?
Thanks
Ulrik


'67 250 SL Papyrus White 113043-10-000023

[hands_aus]

Ulrik,

If you have the fuel mix too lean you will achieve 1.5-3.0% CO at 800 idle but you will find the car won't run well if at all.

I think the later 280SLs had the lower % CO levels but all the rest have 3.5-4.5% CO

Notice that the Haynes also refers to the 250SL engine as an M114 not the 129.

Bob Smith (Brisbane,Australia)
RHD,1967 early 250 SL, auto

[A Dalton]

They run best at 4.5 at idle ... best rpm transfer , best idle , and cooler..
 If the setting on the back of the pump is correct, you should be able to increase the rpms by leaning out the air bleed screw. This means the pump is slightly rich, but that is where you want it. If the rpm can not get an increase over 800 rpms with opening the bleed screw, then the pump should be inrichened one click and retry... this is the final fine tuning of the system and is only done as the LAST adjustment after a tune..
 If one uses a vac gauge to do these adjustments [ which I prefer ], one wants to get the highest vac reading and then enrichen util the rpm just starts to drop withoutout vac drop.... highest rpm is leanest condition , so that is why you enrichen after this is found.

[Cees Klumper]

Ulrik - I believe the lower CO levels are for (US) cars with the emissions controls. Last weekend I adjusted my car's CO level from the Haynes manual and that is what I noticed. I adjusted mine to 3,6% (it was at 4,6%) in order to be able to pass the annual regulatory check-up and the idle is indeed not as smooth, particularly when the engine is not completely warmed up, as when I had it at 4,6%. Although that could also be impacted by the ignition timing, which I adjusted slightly as well.

Cees ("Case") Klumper in Amsterdam
'69 white 280 SL automatic