Inline fuel pressure gauge question
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Racer
Joined: May 2001
Posts: 401
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From: Carlsbad CA
Inline fuel pressure gauge question
In my quest to get my Edelbrock carb set up, I installed an inline fuel pressure gauge using a T fitting on the fuel line just before the carb. When I run the engine, the needle bounces back and forth very rapidly between zero and a higher number (anywhere from 5 to 10, depending on engine RPM). Is the gauge bad, is my fuel pump bad, or is this normal? Edelbrock recommends a fuel pressure at idle of 5.5, so I know I need a fuel pressure regulator, but I have to get a good reading on the fuel pressure to dial in the right setting on the regulator. Thanks in advance for any insight.
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Le Mans Master
Joined: Aug 2000
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From: Semper ubi, sub ubi
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Re: Inline fuel pressure gauge question (thebruce)
Mechanical fuel pump is a diaphram pump that is driven by an eccentric on the camshaft, it is sort of like a bicycle pump in the sense that it does not put out a constant pressure. On each revolution of the camshaft the diaphram is flexed and the fuel pressure rises, when the lever relaxes the diaphram the pressure drops. So on a slow idle the the pressure will bounce noticeably. When the car is really cranking the rpms, the pulse will be less noticeable (because the time between strokes is shorter.)
