A diesel engine is fed fuel by an injection pump, which needs to be working in tandem with the fuel injectors. Tuning a diesel pump refers to adjusting the timing of the pump to work with the injectors as they spray fuel into the pistons of the engine. While this sounds complicated, it is a procedure that requires only a few tools and can be done over the course of an afternoon.
Twist the screw cap of the diesel pump counterclockwise to remove it.
Use the 13-millimeter socket wrench to loosen the lock-nut on the Torx screw. If the lock-nut does not turn freely, apply a small amount of oil to the screw and lock-nut, then loosen it. Do not remove the lock-nut, just turn it enough to loosen it on the Torx screw.
Turn the Torx screw clockwise 1 1/2 turns with the T-27 Torx bit. Tighten the lock-nut. Replace the screw cap onto the diesel pump.
Attach the pyrometer to the exhaust of the vehicle. Drill a 3/4-inch hole in the exhaust pipe, 6 inches below where the engine manifold connects to the exhaust pipe. Insert the clamp bushing of the thermocouple into the hole. Use a blowtorch to heat up the clamp bushing until it is red hot and has welded to the exhaust manifold. Wait 1 hour for the metal to completely cool. Insert the thermocouple lead into the bushing.
Loosen the screws on the thermocouple wires. Slide the ring terminal end of the red lead wire onto the screw with the red thermocouple wire attached to it. Tighten the terminal screw. Slide the yellow lead wire ring terminal onto the screw with the yellow thermocouple wire attached to it. Tighten the screw. Slide the provided protective plastic sleeves over the screw terminals. Run the lead wires to the back engine wall, through the access port and into the cabin of the vehicle.
Cut a 2 1/16 inch hole in the dashboard with a hole borer tool. Insert the pryometer gauge into the hole from the back of the dashboard. Insert the light wires of the pyrometer to the instrument light switch clip.
Connect the lead wires that you fed into the cabin to the screw terminals located on the back of the pyrometer. Attach the yellow lead wire to the positive terminal, marked with a "+" sign, and the red lead wire to the negative terminal, marked with a "-" sign. Tighten the terminal screws to secure them in place.
Warm up the engine, and then drive it for 15 minutes -- up a hill, if possible -- to make the engine work hard. Monitor the pyrometer. When the diesel pump has been tuned properly, the exhaust temperature will not go over 1,250 degrees Fahrenheit. If it does, you will need to do another adjustment.
Loosen the four 17-millimeter Hex bolts located on the sides of the injection pump. Take note of the injector's position, then carefully lift it up and turn it 2 degrees counterclockwise. Tighten the hex bolts. The engine exhaust should now run at 1,250 degrees Fahrenheit or below.
