1999 Volvo Penta "WT" Models Workshop Manual, Page 12Get this manual
Tuning The Engine _ The purpose of an engine tune-up is to restore power and performance that has been lost through wear, corrosion or deterioration of one or more parts or componentsIn the normal operation of an engine, these changes can take place gradually at number of points, so that it is seldom advisable to attempt an improvement in performance by correction of one or two items onlyTime will be saved and more lasting results will be obtained by following definite and thorough procedure of analysis and correction of all items affecting power and performanceEconomicaltrouble-free operation can better be ensured if complete tune-up is performed once every yearpreferably in the springComponents that affect power and performance can be divided into three groups: Components affecting compression Components affectinn ignition Components affecting fuel system Tune-up procedures should cover these groups in the order givenWhile the items affecting compression and ignition may be handled according to personal preference, correction of items in the fuel system group should not be attempted until a!1 items affecting compression and ignition have been satisfactorily correctedMost of the procedures for performing complete engine tune-up will be covered in greater detail in this manualThis section will deal mainly with the order of procedures involved in tuning the engine