What ragulates how long the pump runs when you first turn the key?

 

The fuel pressure regulator regulate the pressure and the pump runs about 5 sec
When the key is turned on.

 

The regulator has a vac hose going to it. And no elec wires. When does it know to shut off.

 

when the correct fuel pressure is achived

 

The PCM initially pulls the fuel pump relay shut to energize the pumps and pressurize the fuel rail prior to start.

 

But what monators this pressure to turn it off?

 

Is this a timed thing or a pressure thing?

 

The PCM energizes the system for preprogrammed period of time. It has nothing to do with reaching a pressure value. It is a time factor in the PCM

 

And an interesting to note-the fuel pump relay always has power right there. The PCM merely places a ground onto the control windings of the relay to pull the primary contacts shut. I do not know whether the PCM uses programing or a simple time delay relay inside to do its work here.

 

I wouldn`t think the pmc or emc would be guessing at it. There has to be resister in there doing some thing I would think.