Q1.) Explain in detail, why is the adjustment of Pmax necessary and the procedure to be followed?
Ans. If fuel oil valve, piston, inlet and exhaust valves, as well as turbocharger and charge air cooler, are working correctly and the compression pressure Pcomp is normal, the maximum combustion pressure Pmax will indicate the injection timing for the fuel oil pump.
If Pmax is too low it indicates that the injection timing is delayed.
If Pmax is too high it indicates that the injection timing is advanced.
The injection timing can be altered by inserting or removing shims under the thrust piece on the roller guide, thus changing the measure "X", see fig.
Thinner and/or fewer shims ( increase of the distance “X”) results in a delayed injection timing and aPmax. Thicker and/or more shims (reduction of the distance "X”) results in an advanced injection timing and a higher Pmax.
If the distance “X" is to be changed the trigger (1) is used for dismantling of the thrust piece (2), where after the thickness and/or the number of shims (3) can be changed.
By changing "X" with 0.10mm the maximum combustion pressure is changed with approx. 1 bar (depending on engine type). After replacement of shims the thrust piece is re-mounted in the roller guide (4) with a soft hammer (5). When changing "X" it must be ensured that the distance between the upper edge of the roller guide housing and the thrust piece on the roller guide is not exceeded, when the roller is resting on the circular part of the fuel cam.
In all cases "X' must be checked and adjusted , if necessary, when fuel oil pump, roller guide, roller guide housing anchor camshaft section have been replaced/dismantled
Note: If several fuel oil pumps, roller guides, roller guide housings and/or camshaft sections are dismantled at the same time it is advisable to number the parts in order to facilitate remounting and adjustment.
