Best Fuel Pressure gauge?

[SSGN]

Looking for input on the best 1 1/2 fuel rail/Regulator fuel pressure gauge? Brand and liquid filled vs standard. I have tried a few in the past and they were never very accurate when engine bay temps got warm and also didn't last long.
Thanks in advance

[1320racer]

Kevin, I can't say whose is best but I can tell you that you don't want a liquid/glycerin filled gauge.

That said, my advice is to remove the gauge after the fuel pressure is set.

[Jeff Niceswanger]

You want the stepper motor ones. Deadly accurate. They make them in 60-210 Water Temp also. This is a AutoMeter 4463-SP 0-100 . The also have 0-15 also. I have one (0-15) laying downstairs if that's what you need.


https://www.autometer.com/2-5-8-fuel...peak-warn.html

https://www.autometer.com/2-5-8-fuel...peak-warn.html

https://www.autometer.com/media/cata.../4/4470_30.jpg

[Kirk Morgan]

Thats interesting. I have found the liquid filled gauges to be accurate. At the instruction of Aeromotive i pull the rubber plug out of the gauge to equalize the pressure. We just installed a Race Pack and the reading on the gauge and the data logger were the same.

[1320racer]

All that tells me is it’s not accurate.

[SSGN]

I have heard the liquid filled gauge can change as the engine compartment gets hot the fluid changes viscosity. Thanks Jeff for the input also but I am only looking for small rail mounted unit. I just want to have a look at the fuel rail periodically. I have a 2 1/2 gauge with 3 ft hose to verify if I think there is a problem.

[Dyno]

I had a couple of the cheap ones go bad. I bought liquid filled one from Red Horse, try that next

[1320racer]

Red Horse = chinese junk!

[Dyno]

The great thing is that I can not read anything Ed posts because I have him blocked. I recommend everyone to do the same. The site is much more enjoyable to go to since I did that!

[1320racer]

Kevin,

Marshall makes most if not all the liquid filled gauges and private labels them for others as well they do the same for all gauges. I suspect they are made in china.

https://www.marshallinstruments.com/index.cfm

This is from their FAQ...

My liquid filled gauge isn't reading correctly, do I have a faulty gauge?
The gauge is most likely fine and you are seeing the effect of temperature change on the filled gauge.

How do I fix it?

Cut the Nipple Plug
Vent the gauge
Cool the gauge to a known reference temperature

Cut the Nipple Plug

Most of our 0-15 PSI gauges come with a nipple plug. Install the gauge so that the nipple plug is facing up, then cut the nipple off the plug. This will allow the case pressure to be equalized at all times ensuring accurate readings regardless of gauge temperature.

IMPORTANT: DO NOT cut the nipple on the plug if the nipple is not facing up.

If your gauge does not have a nipple plug then see below for instructions on how to vent the gauge.

If your gauge is installed in a position where the fill plug is not facing up then see below for instructions on how to cool the gauge to a known reference temperature.

Venting the Gauge

Only vent the gauge if the fill plug is facing up (air bubble below the the fill plug location). If your gauge is installed in a position where the fill plug is not facing up then refer to the instructions on how to cool the gauge to a known reference temperature.

Venting is easy to do and takes seconds. To vent the gauge carefully push the side of the vent plug (the part under the plug lip) with your thumbnail to equalize the gauge case pressure with the atmosphere (reference pressure). Keep the fill plug vented for 2-3 seconds to ensure the case pressure is allowed to equalize with the outside pressure. Do not remove the plug. See photo below for an illustration of how to vent the gauge:

Venting a liquid filled gauge to equalize case pressure.

It is OK if some liquid also escapes, just wipe any liquid that escapes off with a cloth. Loss of the liquid fill will not affect operation of the gauge.

How often should I vent the gauge?
To ensure an accurate reading you should vent the gauge whenever taking a pressure reading.

Cooling the Gauge

If you can not install the gauge in a position where the fill plug is facing up:

Before installing warm the gauge up to room temperature (this is your reference temperature).
Vent the gauge (see "Venting the Gauge" above).
Install gauge.
Ensure that the gauge is at the reference temperature when taking a pressure reading. If the gauge is hotter than the reference temperature then wrap a cool wet towel around gauge case to cool the gauge to your reference temperature. If the gauge is cold then wrap a warm wet towel around gauge case to heat gauge up to your reference temperature.
Ensuring that your gauge is at your reference temperature when taking a reading will minimize any pressure offset due to temperature change.

Why is venting/cooling necessary?

All mechanical liquid filled gauge cases are sealed (to keep the liquid in) so as they heat up pressure will build up in the case (approx 1psi for every 30-40F temperature change). This case pressure exerts a force on the mechanical movement and offsets the actual process pressure. This effect is minimal and typically only noticeable when measuring lower pressures, i.e. on a 0-15 psi gauge.

American National Standards Institute (ANSI) approves American National Standards which include the American Society of Mechanical Engineers (ASME) standard ASME B40.100. This standard addresses venting of sealed gauges within the following section:

Sealed Cases: Liquid filled or not, will exhibit error as a result of exposure to ambient or media temperature different from that at which the case was sealed unless compensation is provided. This error is caused by internal case pressure changes and depends on fill media, extent of fill and other factors. The error is constant over the entire scale, and if the temperature is stable, within limits, it can be corrected by resetting the pointer. An increase in temperature generally causes an increase in internal case pressure with a resulting decrease in indicated pressure. The opposite occurs for a decrease in temperature. For a given temperature change, the percentage of error noted on the gauge is a function or the range of the gauge. If, for example, the temperature increase causes the internal pressure to increase by 3 psi, then on a 30 psi gauge, this will cause a 10% error, whereas on a 0-100 psi gauge, the error will be 3%. For higher ranges, the percentage of error becomes proportionately less.

Maximum Temperature Limits

To ensure longest, possible life and accurate readings, pressure gauges that have soft-soldered pressure joints should not be exposed to process or ambient temperatures over 120 degree F. This is especially true of pressure gauges with liquid filled cases, due to the expansion of the case fill fluid. Long term exposure to temperatures in excess of 120 degree F may cause discoloration of dials and fill fluids, as well as hardening of the case seals and possible fill leakage. Gauges with silver soldered or welded pressure joints should not be exposed to process or ambient temperatures over 190 degree F.