Fuel Pressure Regulator - Should it hold pressure when turned off?

[veets]

Fuel injection system - I measured the pressure of the fuel system and when I press the start button and don't start the engine, I get about 36 PSI.  When I start the engine, I get a pressure reading that fluctuates (needle rapidly oscillating between 30 and 40 psi).  Is this normal? 

When I turn off the engine, the pressure in the system slowly decays.  It takes about 15 seconds for the pressure to drop to 10 psi.  Is this normal?  or is the pressure regulator supposed to hold the pressure longer?

[riots100]

Yes, seems fairly normal.  Pressure is not expected to hold when you turn off the engine.  pressure fluctuations occur due to opening and closing of injectors.

[veets]

Thanks.  I keep reading that you have to be very careful because it is a pressurized system but I have yet to take off the fuel lines and get much of any pressure.  it always seems to be down close to zero pressure within a couple of minutes.

[kris]

Never had a problem the few times I pulled fuel lines. Simply found that the tank would leak fuel if you didn't plug the line. Someone mentioned a wooden golf tee here somewhere....

[K1300S]

Yes, seems fairly normal.  Pressure is not expected to hold when you turn off the engine.  pressure fluctuations occur due to opening and closing of injectors.

not exactly correct in my experience.  fuel pressure should be pretty steady when engine  is running.  injectors opening causes very little loss relative to the volume of fuel in the lines.  post a video of what the gauge looks like with engine running.

and when you shut the bike down, the pressure should NOT drop radically.  the pressure should hold pretty high for a long time.  if it is dropping fast, there is a pressure regulator issue , fuel pump problem or an injector stuck open.  there is a specific test for shut down pressure in the shop manual i believe.

[Martin]

+1 Marshall my bike will hold pressure for a fair while.
Regards Martin.