BenzWorld Junior Member
Date registered: May 2008
Vehicle: 1993; 300E; 2.8
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i am getting poor gas mileage , and have therefore been researching the fuel pressure regulator. i have a couple of questions regarding the regulator.
1. i specifically remember testing the fuel pressure regulator about a year ago: i started the vehicle and then pulled the vacuum line off of the regulator and immediately noticed a small surge in idle speed.
However when checking the fuel pressure regulator yesterday, using the aforementioned method, there was no difference in idle speed at all. i was wondering could this be an indication that the fuel pressure regulator is in need of replacement?
from what i've learned about the FPR, vacuum is applied to it via the manifold, which then reduces the fuel pressure in the fuel rail, as the throttle is increased , less vacuum is applied to the FPR, thus increasing fuel pressure in the fuel rail. is this correct? now when i remove the vacuum from the FPR ther is no longer an idle speed surge(no change in idle), which leads me to believe that the FPR is shot and constanly keeping the fuel pressure in the fuel rail at a higher than necessary value, and thus leading to my poor fuel mileage.
and 2. upon visual inspection of the FPR i noticed , what looks like oily residue and some crud on top of the FPR. are they(FPR) perhaps filled with anything?
sorry for the long post!
Last edited by timmyr; 04-08-2010 at 01:48 PM.