I am definitely not an expert on this type of problem, but anyway if it were my car, I would first check to see whether with the engine cold the warm-up device opens (air suction which can be heard by either taking the air filter off the FI pump or by holding a piece of platic tubing to the intake holes on the filter) and whether it shuts off at the appropriate temperature as indicated in George's post. If that checks out, I am not sure whether the chance of that being the problem is very high, but then I might take the thermostat housing off just to make sure it can move freely etc. I would also check for air leaks on the tube that runs from the FI pump to the cold start valve on the intake manifold, plus I would check whether that valve is leaking or not (test procedure covered in previous posts, involves taking out the small -7mm?- test bolt our of the housing). I would also check whether the fuel linkage is adjusted properly, both the intake venturi and the FI pump at their stops at idle, and the air screw on the intake manifold at least partway open, no air leaks there ets. Then the distributor - is it the correct type and are there any air leaks on the vacuum line. Assuming all that checks out, I would let the engine warm up and set the idle mixture using the Gunson tester. I have one and it works very well - when I first started my newly rebuilt engine last April the idle mixture was at a whopping 10% and I had to lean out the mixture by 7 or so clicks. Now it's steady at 3,5-4%. If you cannot get the idle mixture to the correct value when the engine is warm, while the warm-up device and the cold start valve are functioning properly, and the linkages are set up correctly, then I would start to suspect the FI pump and turn back to this forum for professional advice! Oh and maybe it's worthwile to check the hose + valve going to the brake booster?
Cees Klumper in Amsterdam
'69 white 280 SL automatic
