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Old 08-09-2020, 09:12 PM
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Originally Posted by patrickt View Post
I have an in-line, liquid filled, fuel pressure gauge right there at the feed to the Holley. You have to learn how it is affected by the temperature change under the hood to really appreciate it. The first time you see it reading zero psi and your engine is running like a champ is the first lesson....
Yes, a liquid filled gauge will do this because the gauge is sealed, and the internal pressure varies with temperature.
The small amount of air is a cushion at normal atmospheric pressure. The gauge internals are referenced to this.
Raise the internal temperature and pressure, and then the gauge will read correspondingly lower.

Adjusting fuel pressure should be performed with a cold engine, at about 20 degrees C.

I have had better success with non-liquid filled fuel pressure gauges.

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