Question 47 MODE01 - Chief MODU Engineer

The Correct Answer is B **Explanation for Option B (binding of pump moving parts):** Uneven bolt tightening during the installation of a fuel injection pump can cause the pump housing (casing) to distort or warp slightly. This distortion is often minute, but it is enough to misalign the internal rotating components (such as the cam ring, plungers, or rotor) relative to the now-stressed casing. When these extremely precise internal components are forced into a slightly distorted housing, the resulting friction increases dramatically, leading to **binding** (excessive friction or sticking) of the pump's moving parts. This mechanical failure can prevent the pump from operating correctly or cause rapid wear and seizure. **Explanation for Incorrect Options:** * **A) improper pump-to-engine timing:** Pump-to-engine timing is primarily set by the adjustment of the pump drive gear or coupling relative to the engine's camshaft/crankshaft, or by physically rotating the pump body (static timing). While improper installation might indirectly affect timing if the mounting flange isn't seated correctly, uneven bolt tightening itself is a distortion issue, not the primary cause of static timing error. * **C) high torsional shock to fuel lines:** Torsional shock (twisting force) in fuel lines is typically related to high-pressure pulsations generated by the pump's normal operation or abrupt changes in engine load, not the torque applied to the mounting bolts during installation. * **D) ignition delay:** Ignition delay is a combustion characteristic primarily influenced by factors such as fuel quality (cetane rating), compression ratio, injection pressure, spray atomization, and combustion chamber temperature. It is a symptom of poor fuel-air mixing or delayed auto-ignition within the cylinder, not a direct consequence of unevenly torqued mounting bolts on the injection pump body.