The fuel pump pressure may vary by vehicle. However, on average the fuel pump pressure with the engine running should be between 4-6 psig.
If the engine is not running the pressure should be 35 to 40 psi. If the engine is running the pressure should be 30 to 45 psi.
If engine is running then the answer is yes. And pressure will stay in the fuel line for some time after you shut the engine.
With key on engine not running pressure should be 9 to 13 psi Engine at idle pressure should decrease by 3 to 10 psi on a throttle body. On a multi port injection key on engine not running pressure should be 41 to 47 psi. Engine running at idle pressure should decrease 3 to 10 psi. Central multiport fuel injection key on not running should be 58 to 64 psi. Engine running at idle pressure should decrease 3 to 10 psi. Central sequential electronic fuel injection key on not running pressure should be 55 to 61 psi. Engine running at idle pressure should decrease 3 to 10 psi.
The fuel pressure for a 1994 Chevrolet Z28 with the LT1 engine typically ranges from 43 to 47 psi (pounds per square inch) when the fuel pump is running and the engine is off. When the engine is running, the pressure should remain within this range. It's essential to check this pressure with a fuel pressure gauge to ensure proper engine performance and fuel delivery.
key on engine not running 58-64 psi engine running at idle pressure should drop by 3-10 psi
On an Olds Cutlass 2.8, the fuel pressure should be between 40 and 47 psi with the engine off. With the engine running, it should be between 30 and 44 psi.
41-47 psi, engine off, fuel pump running.
With ignition "ON," engine "OFF" and fuel pump running, pressure should be 385-430 kPa (56-62 psi).
Assuming this is the 4.3 L engine, 60 to 66 psi with fuel pump running, engine off.
Should be about 60psi running, should hold more than 50 with the engine off.
With the key on pump pressure should be 40 - 47 psi. This is with the engine not running.
It should be 30-35 psi with the engine running.