I came across this video about liquid filled fuel pressure gauges which may help some members troubleshooting.

 

Dont install liquid filled gages under the hood

 

Three minutes and fourteen seconds. The guy must get paid by the time he wastes. But that's common with Youtube videos, where they drone on and on and on about...nothing important or relevant. And then, instead of imparting useful info, he sends you to a Corporate Press Release, as if they were the ones who have The Only True Solution to the problem. The problem is not the gauge, per se. The problem is that folks who sell liquid-filled gauges don't bother to tell you how to use 'em because it's a hassle, and some folks won't buy them.

Here's my take. Get out your stop-watch. Let's see how long I need.

Liquid filled gauges were developed for high-vibration use. The damping fluid expands and contracts more than the gauge housing from temperature swings. This creates pressure differences inside the gauge that interferes with the mechanism. The gauge will have a rubber plug in it. MOUNT THE GAUGE SO THE RUBBER PLUG IS STRAIGHT "UP"!

Any time you want to take a pressure reading, remove the plug. You don't have to take it all the way out, but you need to "burp" the plug to equalize atmospheric pressure with the pressure inside the gauge. The next time you take a pressure reading, burp the plug again. It's a total pain in the ***, but absolutely required any time there's temperature changes where the gauge is mounted.

If you're really careful, you can poke a small hole in the rubber plug with a needle. Then the plug is "vented". In extreme vibration environments, some damping fluid can leak out; or some outside contamination can get in, but then you shouldn't need to "burp" the plug every time you want a reading.


Annnnnnd...STOP.

How long did I need?