Thanks Josh you are right the gauge measure inches of mercury not atmospheres.( .489 vs 14.7 lbs) I did an experiment this morning and our Universal M35 uses an electric fuel pump made by Facet that runs at 6-8 psi. The gauge running shows 1 inch of mercury or just around .5 lbs and it will generate at least 7 inches of mercury vacuum with the fuel valve shut off or about 3.5 pounds of vacuum. I did not take it further into vacuum because that’s all I wanted to know. If the vacuum reads more than 1 inch of mercury there is a restriction somewhere, dirty primary fuel filter etc. Something else to consider, a Facet fuel pump has a screen filter in the bottom if it’s not pulling fuel, although the primary is supposed to catch any contamination first. Let us know how you make out Tom! Len Mitchell Crazy Legs 1989 37+ Midland On.
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