Yeah, you're doing it wrong.
Straight from stanadyne. "1. Remove the three governor cover screws and washers and set aside.
2. Move the governor cover down towards the top of the pump from a
position further toward the drive shaft end (means pump driveshaft aka front of emgine) than its final assembled position as shown in Figure 11 to ensure the pivot arm is positioned on the proper side of the linkage hook.
3. Just before the cover seal touches the housing, slide the cover into alignment, install the cover screws and washers, and tighten screws to 35-45 lbf.-inches (4.0-5.1 Nm)."
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The fsv arm does not go "behind" the arm in the pump. Goes in front of it.
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