that even though the engine oil level may be full, it doesn't mean the engine has oil pressure. Oil pressure can be fine even though the oil level may be quite low. OTOH, the level can be full and there still be low or no oil pressure. If you indeed have no oil pressure, immediately shut down the engine and don't restart till the problem is solved. Checking the dipstick because of low/no oil pressure may be the first thing to look at, but it doesn't tell you anything more than the level.
