What is a likely cause of hard starting after a vehicle has sat for some time if fuel pressure reads 32 psi?

A leaking fuel pump check valve is indeed a likely cause of hard starting after a vehicle has sat for a while, even if the fuel pressure reads at 32 psi. The function of the check valve in the fuel pump system is to maintain the fuel pressure in the lines when the engine is not running. If the check valve is leaking, fuel pressure can bleed down over time, leading to difficulty in starting the engine because the fuel system needs to build pressure again before the engine can fire.

In this scenario, although the gauge reads 32 psi when checked, this pressure may not be stable or sustainable after the vehicle has been off for a period. The initial pressure reading could represent fuel that has not yet dissipated due to a failing check valve. Once the vehicle sits and the check valve allows fuel to flow back into the tank, the pressure can drop to a level that makes it challenging for the engine to start.

The other causes, while valid under different circumstances, do not explain the hard starting specifically after sitting for some time in the way that a leaking check valve does. Low fuel pump output might not create issues until the vehicle is under load or demands more fuel, leaking injector o-rings would typically result in fuel leaking into the intake or