BenzWorld Senior Member
Date registered: Jan 2005
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RE: 250 SE 108 hard to start cold
Ha Ha ,as Soon as I saw the gum trees and the mozzie nets on the front i realised you are in OZ.
To adjust the idle mixture correctly is a real chore actually.
It involves getting the acelerator linkage is step between the throttle body and the injection pump.
The pump mixtue is set by that thumb screw on the back of the pump.It must be done with an analyser ,the car must be warmed up and idling,the mixture (C/o) level noted.If too rich ,STOP the engine.PUSH in the the little round knob and turn 1 Click to the LEFT,resart the engine and check C/O levels again ,if too lean turn to the right.
Never push the knob in with the engine running.the knob will engage with the govenor and destroy the pump.
I usually start here with these jobs,and then to further tune it,i remove the push rod from the pump to the cross arm and set the idle with the car in top.(and a good chock under the wheels[:D][:D]
As a rule of thumb,if the idle speed goes up and down slightly,the mixture is too rich and if the engine seems to vibrate or not run on all six ,it's too lean.
Whatr you did to the waxstat is getting more common as these cars age and people insist on using ordinary water.Fatal in someparts of OZ as it's like using acid in the radiator.
One last thing,get under the car and clean the tank bung filter,and replace the fuel lines to the pump,they will be buggered by now and use quality EFI hose.
The secret Merc mechanic trick is to also shove a peice of wire down the return pipe in the fuel tank,(the samller upper steel pipe) i 'll bet it's blocked.In fact i've had to replace some tanks because the pipe was actually Rusted up.it's a real common problem on all the W110 -109 cars.