Is it an M pump or an MW?
If it is an MW Pump it will have a 14mm Lock Nut where the Blue Arrow Points. You Loosen that; I use a 14mm Crows Foot on a 3/8" and a Ratchet Wrench.
And, turn the part the Green Arrow Points to with a Screw Driver to adjust the idle speed and turn the 14mm Nut to lock it in place. do not tighten the Nut too mucha as below it is Aluminum.
Sorry about the recycled photo!
If you have an M Pump page down on the long #1 post at the site at the bottom; and there is a diagram of the Governor of the M pump showing the Idle Adjustment at the rear top of the Governor labled #3 and #3a
http://www.superturbodiesel.com/std/ip-full-load-adjustment-procedure-for-mw-pumps-t-189.html