weather/rain screw up mech FP gauge??

i have had some strange fuel pressure readings from my mechanical fuel pressure gauge.

i have the gauge mounted on the backside of my cowl induction hood.

originally when i put the mech gauge on, the FP readings were rock solid, then after a while the FP would start fluttering.... would read right around the area it should be, but bounce around 2-4 psi. at idle it would really get erratic.

before i start tearing into the car. i took the mech gauge off and hooked it up to my brothers mustang, a stock 91 LX, fired it up with the gauge on and it read rock solid. before i got a chance to try it on my car again i dropped the gauge and broke it.

so i had to buy another guage.
hooked the new gauge up to my car the reading were rock solid. was fine up until a few days ago. the car had been sitting for a week or so without beeing drivin. the FP starts fluttering again. just a few PSI of what it should be rock solid at.

sometimes it was bad sometimes it was a little better and almost smooth. still pretty erratic at idle, will jump like 8-10 psi at idle.

so i figured the regulator might be going south, so i went and bought a new stock style regulator, non adjustable (dont need to mess with FP since i tune the car with a tweecer) took off the adjustable i had and put the new one on. fired the car up and the same problem. would flutter around. car seems to run and start good. revved it up a few times and it settled down and seemed to sit pretty solid around 33-34 psi

i figured there may be air in the line, unhooked the braided fuel line coming from the schraeder valve location. hooked up back up. unhooked the line from the gauge and just for grins i was going to try and turn the key on and while fuel was shoot out of the line i was going to stick the gauge on and tighten it before the few secs of fuel flow stopped to try and get all air out of of the line. well this was a dumb move because i managed to get the gauge SOAKED in gas and now the gauge wont work at all. so i broke ANOTHER gauge. i grabbed another smalle FP gauge i used to use. i hooked it up to the rail and fired her up and the FP was rock solid on this gauge. reading around 30-34 or so with vac line and 39-40 with no line.

drove the car and the car "feels" like it drives a tad smoother with the new regulator on the car. this is probably a placebo though so i dont know....

so has anyone fought any fluttering fuel pressure problems with an autometer gauge (mines actually the ford racing autometer gauge)

i guess i am stuck buying another gauge, i like having the gauge mounted on the hood, what about gasoline would ruin the gauge??? perhaps it could free up after sitting for a while????

yeah i did hook up a small gauge thats sitting by the rail now, it seems to be reading smooth now. like i said the car seems to be running smooth and dandy. so at this point i am still confused to whether its a gauge issue or something wrong with the fuel system.

do you think a fuel filter could cause a problems, its been a while since i have replaced mine.

the fuel pump was put in a month or two ago and dont see how it could be bad, its brand new. a summit 255 lph. still the same walbro pump everyone uses.

i guess i can try a new filter and note any changes...

thanks jrichker!!

i'll give that a try.
and jason i would drill into the NPT side.

the gauges arent liquid filled.

sorry to revive this dead topic but i ended up restricting the fuel flow to the gauge and it seemed to help alot with the needle shake, i didnt use the screw method,

i ended up taking it to work and just tig welding the pipe end shut with some phosphor bronze rod (low melting point to keep from overheating the small fitting)

then i just sanded it flat and drilled a size 60 (around .040) hole in where i welded it shut. threw it back on and it worked good. there still may be a little vibration just barely but that may be the car shaking causing that i dont know, but its steady enough to where i actually know what the FP is.

thanks for all the help