Anyone know what the fuel pressure is post filter on a LLY? Is it measurable 1-2 psi or is it not under pressure? I am curious. I figure there is not a lot of pressure here but I am not sure if there is enough to measure on an electric fuel pressure gauge. I have seen guys running gauges in this location but most are running lift pumps. I guess I am asking if I hook a gauge in this location (bleeder valve) will I get a reading on an otherwise non modified fuel delivery system. Want to mount it to the bleeder valve location, that part I have figured out. Your infinite wisdom as always is appreciated.:thankyou2 <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /><o:p></o:p>

No pressure, you are on the vacum side of the injector pump. About 3" with a new filter & time to change at about 8-10".

Huh?

There is no OEM lift pump to provide fuel to the injection pump - the injection pump pulls fuel from the tank, through the filter, hence the vacuum.

I understand the vacum part the 3", 8-10" part confused me

The 3" is referring to how vacum is measured, pressure is measured in "pounds per square inch" PSI.
Vacum is measured in "inches of vacum" so the 3" is three inches of vacum, the lower the number the less vacum, 3" of vacum is less restriction than 8"-10" of vacum which will happen when the fuel filter is dirty and has more restrictive force on the fuel flow.
I'm not a expert on this but I think the most vacum you can have is 27" which is absolute vacum.
So to answer your question about a guage at the bleeder valve you need to install a vacum guage not a pressure guage unless you install a lift pump then you would need a pressure guage.

Thank you for clearing that up, Boy I am easy to confuse, well I guess a lift pump it is since I am sitting on a useless fuel pressure gauge without it, I love my rationale for purchasing more stuff :ro)

There seems to be little down side to a lift pump, especially since Bosch apparently called for the system to have one anyway.