Hi, I have one of these vacuum guages and I have borrowed Robert Lilley's fuel pressure guage, so I will give your test a try next week. I measured it last weekend at 32 psi unconnected and 39 psi connected -- slightly too high but not enough to worry about, I hope. I forgot to plug the manifold vacuum hose, though, so I need to repeat this measurement. (What does the g stand for in psig?) While attempting to evacuate my AC system, I noticed the MV as 10" to 12" Hg just as you state. Do you think I have a leak somewhere -- I hadn't thought that it might should be 15". Thanks, Michael Townsend 90 Carat Durham NC PS. Finally got my R-134a charged this morning -- looking forward to a cool drive home! > The problem with this spec. is that we don't know (okay, I don't > know--maybe you do) what idle MV is for this spec. As MV decreases, the > fuel pressure at the tee will increase. In other words, if you have an MV > leak and perform this test, you'll measure something higher than 28 psig > for the hose connected test, even if your FPR is mechanically sound. > > Frank Grunthaner suggested that the 10 to 12" of vacuum many of us consider > "normal" for our wasserboxers seems too low and that at least 15" is more > typical for modern gasoline engines. > > Sooo... I performed an experiment to find out what the test tee fuel > pressure would be if my manifold vacuum was 15". I did this by > disconnecting the FPR vacuum hose and plugging it. Then I connected my > MityVac brake bleeder/vacuum diagnosis tool. This tool is a simple > hand-actuated vacuum pump that can pull up to 30" of vacuum. It can also > function as a simple vacuum gauge. (The vacuum gauge on this new tool has > a stated accuracy of 2-3% but I cannot guarantee its calibration. ) I > measured 28 psig at the fuel line test tee with 15" vacuum pulling on the > FPR. > > Scott Terry > '85 1.9L Westy "Pearl" > Santa Barbara, CA > Still parking next to other Westys despite the danger... |
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