How can lack of oil pressure prevent my 7.3 diesel from starting?

Oil pressure is vital for the lubrication of the engine's internal components, including the pistons, crankshaft, and camshafts. Without sufficient oil pressure, the engine will not receive enough lubrication, which can cause the components to overheat, seize up, and eventually fail.

In particular, the 7.3 diesel engine in Ford vehicles has a high-pressure oil system that delivers 40 to 60 pounds per square inch (PSI) of oil pressure at idle and up to 100 PSI at higher RPMs. If the oil pressure drops below these specified levels, the engine may not receive adequate lubrication and could suffer damage.

When the oil pressure is too low, the engine's oil pressure sensor will send a signal to the engine control module (ECM) or powertrain control module (PCM). The ECM/PCM will then turn off the fuel injectors, preventing the engine from starting. This is a safety feature to protect the engine from severe damage in case of insufficient lubrication.

Therefore, if your 7.3 diesel engine is not starting, it is essential to check the oil pressure and ensure that it is within the specified range. If the oil pressure is too low, you should investigate the cause, which could be a faulty oil pressure sensor, a low oil level, a plugged oil filter, or a malfunction in the oil pump or oil pressure regulator.