Injection Pump Adjustments

[gkaralus]

Hi, I am trying to help a friend that has a 250sl in his shop. This car has been the girlfriend from every mechanic in town, you all know what that means. The car came towed because the pump was installed wrong. With the instructions here (the 20 degree atdc thing ) we got it to start. I made them check the butterfly valve stop and the 233 mm rod, ok, but it seems that someone messed with the injection pump stop.  They got it running by disabling the wrd device.

Still the ip lever has to rotate about 15 degrees when the butterfly is closed to get it to idle. It seems that the mixture when the ip is in at stop is too lean. There were no shims under the wrd. Should shims be added, one by default? and what thickness?

[Cees Klumper]

Make sure you try out the 'slotted screw idle mixture adjustment' at the back of the FI pump before adding shims to richen the mixture across the entire RPM range. Normally these FI pumps wear rich, not lean. With the engine off, turn in the slotted screw (push in until you feel it engaging, then turn clockwise to enrichen the mixture at idle) and see if that fixes the problem first. Make sure you do the 'linkage tour' as well (use the search function). Good luck and others please chime in here.

[ja17]

Hello,

Make sure the fuel filter is clear and you have a good supply of clean fuel at the correct pressure and volume.

Yes, if your fuel supply is correct it sounds like you are running lean. Splitting the linkages and checking the running engine at other speed ranges will also tell you if  your engine is running lean at all speed ranges. Adding shims will richen the mixture at all speed ranges. Just turning the idle mixture thumb screw on the  back of the injection pump will only change the mixture at lower speed range (1700 and below).

[wwheeler]

What are the engine RPM ranges for the adjusting screws on the IP? I know there is the knob for idle and two others for higher speeds.

My engine runs a little lean at midrange and at higher RPMs according to the "Blacklick CO Meter" test. I am making some oval shims out of .003" copper shim stock (any problems with copper?) for the WRD and will start there first. Should I start with one .003" shim or use two for a total of .006"? Any feel for that? The two shims on there now are .012" and .004".

My initial tests show that the midrange RPMs seem to be leaner than the upper range. If that still holds true after shimming the WRD, I may want to adjust the midrange screw on the IP.