Hi,
   I am undergoing repairs on my 1986 K100RS.  It is new to me and I am not familiar with its operation.

  I've read in the workshop manual, that fuel pressure from the pump to the injectors, is lowered via a regulating valve.  But I can't find out if the pump should cut off once the fuel has reached line running pressure.

 My concern, is that when I turn the ignition on, the fuel pump just keeps operating contiually.  I would have thought that the pump would be controlled to cut off, once it has reached the operating pressure.  Is this normal or do I have a problem?

best regards

geordie boy

If the pump were to cut off, you'd lose pressure in the line to the injector rail and the motor would stop. So yes, the pump runs continuously

The pump should not run until you press the start button and for 1.5 seconds after you release the button if the engine is not running.  The pump should run all the time while the engine is running because the pressure has to be kept constant.

RicK G wrote:The pump should not run until you press the start button and for 1.5 seconds after you release the button if the engine is not running.  The pump should run all the time while the engine is running because the pressure has to be kept constant.

Thanks RicK G,
                   so the fuel pump is only energised when the start button is pressed!  Thought it was strange for it to run continuous with only the ignition switched on.  Looks like I've got a bit of diagnostic work to do to cure the problem. 
 If you, or any members, have come across this problem before, I would appriciate any advice.

best regards

geordie boy