The fuel control rod actually controls the amount of fuel that the injector pump sends to the injectors. If it is gummed up it will not allow the fuel to flow correctly. Sometimes they stick shut, sometimes wide open and sometimes just gummed to where it won't idle below 1000 rpm.
Your description of the fuel stop leads me to the gummed up problem.
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The low pressure fuel is the grey shading, it flows down to area of the spill passage. When you use the foot throttle it will move the fuel control unit which in turn moves the plunger sleeve. The more the plunger sleeve uncovers the spill passage the more fuel will be allowed in the spill passage and then on to the injectors. If any of this is gummed up (your brown residue description) it will affect the fuel flow.