Hi! I'm getting ready to install my Bosch Design III's from South Bay this thursday and I want to install the adjustable FPR i got at the same time since the plenum will be off.

I have measured the fuel pressure so that I have a reference what is was before I changed anything, and if i turn the key on with engine off it goes up to 49 PSI. 100% original fuel system, stock regulator, Brand new OEM fuel pump (Carter) and brand new fuel filter.

Doesn't 49 PSI seem a bit high for a stock fuel system? I bought the AFPR to be able to set my fuel pressure at the maximum allowed stock pressure which is 47 PSI according to the FSM, but my stock pressure is already higher?

I am measuring the pressure at the schrader valve on the rail with engine off and vacuum hose off regulator. If i apply vacuum to the regulator the pressure goes down just like It's supposed to so that works.

Am I supposed to set the pressure with engine running or is it ok to set pressure with engine off? Will there be a difference in reading?

Should I set the pressure to what it is now or is it too high? It would feel dumb to set it lower than it was stock...

This is how connected the pressure gauge


This is with key turned to ignition and off again a couple of times, engine off, vacuum hose off regulator.

 

I may be wrong, but I believe your supposed to check it with the engine running and the vac line disconnected.

 

Just checked the FSM and it says:

CHART A-7
(Page 1 of 2)
FUEL SYSTEM DIAGNOSIS
5.OL (VIN F) & 5.7L (VIN 8) 'TF'3SERlES (PORT)
Circuit Description:
When the ignition switch is turned "ON", the electronic control module (ECM) will turn "ON" the in-tank
fuel pump. It will remain "ON" as long as the engine is cranking or running, and the ECM is receiving
reference pulses. If there are no reference pulses, the ECM will shut "OFF" the fuel pump within 2 seconds after
ignition "ON" or engine stops.
The pump will deliver fuel to the fuel rail and injectors, then to the pressure regulator, where the system
pressure is controlled at 234 to 325 kPa (34 to 47 psi). Excess fuel is then returned to the fuel tank.
Test Description: Numbers below refer to circled
numbers on the diagnostic chart.

1. Wrap a shop towel around the fuel pressure
connector to absorb any small amount of fuel
leakage that may occur when installing the gage.
Ignition "ON", pump pressure should be 280-325
KPa (40.5-47 psi). This pressure is controlled by
spring pressure within the regulator assenlbly

So according to FSM I did it the right way... Weird. Maybe the gauge is off a couple of PSI's or the pressure drops a couple of PSI's when engine is running...