Fluid Pressure vs. Air Pressure

[aerosmith145]

I've seen gauges for air and ones for water, but I've never gotten a solid answer (from home depot, lowes, etc.) as to whether or not they're interchangeable. Is there a difference between the two? Reason why I ask is, I was using one from home depot that just said, "Pressure" below the face, and my fuel pressure always seemed a little off.

My other question is:
The way I've seen lot's of people mount they're gauges, they put them on the pressure line right before the fuel rail, so the gauge is higher than the line. Wouldn't this cause an inaccuracy due to air being trapped inside the gauge (from installation)?

Air compresses and fuel doesn't... so what do you guys think?

[Waramp]

I just rigged up a hose that adapts to the fitting on the fuel rail. I use a regular air compressor guage. I tried the B&M fuel pressure guage kit... Your just paying for the name. The guages both lasted the same amount of time. Dont waste your money on a kit its obvisouly just $10 in parts slapped together.

[bfarroo]

Pressure is pressure. Doesn't matter if its a gas or liquid. The only thing I can see being different is the gauges being designed to be in contact with different chemicals. A boost gauge would probably read fuel pressure if it went up that high but who knows how long it would last being exposed to gasoline. As far as air being trapped in the line the pressure on the gauge should still be the same the air will compress but will eventually get to the point that it will stop compressing and transfer the fluid pressure to the gauge. The air may cause the gauge to bounce some if the fuel pressure is very irratic but shouldn't affect the reading any.




Benji Farr
Green Bay WI
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88 Shelby Z TI 2.2 auto
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