Fuel pressure help
There is a vent on top of the guage. The hotter it gets, the lower it reads unvented. you can unscrew the brass screw on top (?) to vent then return it but there were posts that said drill a .020 in the screw itself to permanently vent the guage. See if this fits your guages description. I know the rubber boot is the vent on top. venting should return you to zero.
found this on Moparts. Note red test gauge and yellow unfilled against unvented liquid filled gauges over heat.
There is a vent on top of the guage. The hotter it gets, the lower it reads unvented. you can unscrew the brass screw on top (?) to vent then return it but there were posts that said drill a .020 in the screw itself to permanently vent the guage. See if this fits your guages description. I know the rubber boot is the vent on top. venting should return you to zero.
found this on Moparts. Note red test gauge and yellow unfilled against unvented liquid filled gauges over heat.
