Yes, key on, engine off, the fuel gauge should work.
The fuel level gauge is in the tank
To adjust the fuel level, you should begin by putting fuel into the 1967 F-250 diesel engine tank. The fuel gauge will rise according to the amount of fuel purchased.
make sure that floating thing in the fuel tank is position right or working. The fuel gauge won't be working right if its stuck in one position. Hope that helps...
With a fuel pressure gauge. Not knowing what year and engine you have I can't tell you what the pressure should be.
You will need a fuel pressure gauge. Connect the gauge to the fuel rail and start the engine. The gauge will tell you how much pressure they pump is putting out.
first have an assistant turn the ignition switch to the on position and listen for the whirring sound from fump pump, indicating pump is operating. If fuel pressure is in question you can install a tee fitting between fuel filter and fuel line and purchase a fuel pressure gauge to connect to the tee fitting. fuel pressure should be at 43psi with key on engine off, and 34 to 36psi with engine idling.
connect fuel gauge to schrader valve on fuel rail. Turn key to ON,do not start engine. The pressure should be 42-47 psi.
Depends on the car. Most should drop to empty when the ignition is off but some cars stay in the same position, they are rare though. (Toyota crown, Isuzu panther)
Check the fuel gauge sending unit, located in the fuel tank. The sending unit could be stuck in the full position.
On the engine there is a test port located on the fuel rail. A fuel pressure gauge can be attached to it. A test gauge can be purchsed from your local auto parts store. With gauge attached, cycle ignition key on and off several times. Fuel pressure should peak between 41 and 47 psi.
You should be able to pressure test the fuel system with a fuel pressure gauge though the service port (Schrader valve). Give us the year and engine info for more details.
If it doesn't supply the proper fuel pressure, need to hook up a fuel pressure gauge to the fuel rail/service port and turn the key to the on position. The fuel pump should prime the fuel rail with gas with the engine off. Most EFI systems run around 43psi, some fords service manuals say mid 30s is ok.