4TNV98 & 4TNE98 Diesel Engine Section 4. Fuel System155• Calculate the difference between the timing indexnumbers (Figure 7-26, (1)) of the fuel injectionpump that you removed and the replacement fuelinjection pump. See Calculation Example below.Figure 7-26Adjusting the fuel injection timing to compensate forthe difference in pump timing index numbers:Calculation ExampleTiming Index NumberOriginal injection pump= 6.8Replacement injection pump= 7.3Difference= +0.5• If the difference between the timing indexnumbers is a positive number, the fuel injectionpump mounting position must be advanced(Figure 7-27, (2)) (rotated away from the engine)as compared to the “standard mark” (Figure 7-27,(1)) by the calculated positive amount, adjust thefuel injection pump to the calculated value.• If the difference between the timing indexnumbers is a negative number, the replacementinjection pump must be retarded (Figure 7-27,(3)) (rotated toward the engine) by the calculatednegative amount.• Each mark on the timing sticker represents 0.5°timing change.The above calculated difference indicates that thereplacement fuel injection pump is to be installedat +0.5° (advanced) from the “Standard Mark”(Figure 7-27, (1)) on the timing sticker.Figure 7-27In this case, rotate the top of the fuel injectionpump away from the cylinder block until the markon the outside upper mounting boss (Figure 7-28,(1)) of the fuel injection pump aligns with the +0.5°mark on the timing sticker.Figure 7-28Tighten the fuel injection pump mounting nuts tospecification. See Special Torque Chart on page143.
