I have taken off the &quot;timing cover&quot; that exposes the &quot;Control Unit Assembly&quot; from the injector pump.  Diesel fuel drips from the &quot;Control Unit Assembly&quot; shaft that goes into the injector pump head and ultimately engages the plunger sleeve.  I removed the Assembly by taking out the two wired screws and find that there is an old O-ring underneath.  The original O-ring is 1/16&quot; section and .45&quot; ID.  I installed a 3/32&quot; section x 1/2&quot; ID O-ring (what I had available), and the drip stopped.  If I tighten the assembly hard to the side of the pump, the shaft binds.  I will go to the Auto parts store and see if I can find a more correct section O-ring.  

I am concerned that the pin on the end of the Control Unit Assembly is correctly engaging the plunger sleeve.  

Is the pin engaged properly if the assembly lands against the body of the injector pump?  Or is there anything else more complicated than that?