Anybody knows what i should be reading for fuel pressure at the fuel rail Test port? At idle, Engine off or on? Also would you know the pressure at this point be the same as the pressure right after the fuel pump, or before the regulator? im dealing with a P0171 code still?

 

It should be around 40-50 psi at idle or just with the key on. Make sure it doesn't bleed off.

Edit - true story under neath me, they did up the pressure in newer Montes

 

fuel pressure should be thisKey On Engine Off 52-59 psi

 

damn so my pressure is ridiculously low and erratic. There should be some pressure left when the engine is shut off but mine drops down to nothing. i got this information from someone incase it may help a member here.
here is what he gave me:

"On this engine, fuel pressure should be 52-59 psi key on engine off. It will be slightly less at idle because the vacuum going to the fuel pressure regulator. 9 times out of 10, when the fuel pressure is low, it is a weak fuel pump. If the regulator is bad or leaking, the fuel pressure will go up to specifications when turning the key on, but then will slowly drop down as the fuel pressure bleeds off. It could be a leaky fuel pressure regulator, leaky fuel injector, bad check ball in the fuel pump or even an external fuel leak will cause the fuel pressure to leak down. Hope this helps!
Source(s):
How to check fuel pressure | Engine Misfire "

 

PS: Thanks a lot dudeS!