weather/rain screw up mech FP gauge??

[Foxfan88]

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????

 

[Mustang5L5]

I've had one on my hood for several years now. It's seen rain and even snow without probs.

I'd suggest hooking up a second FP gauge. Autometer sells small ones designed to plug into the shrader valve. I've been thinking of getting one and installing a T since i hate looking back at the cowl when adjusting under the hood.

You could have a problem with your fuel system. I mean...that's what the whole point of the gauge is right?

 

[Foxfan88]

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...

 

[cenok is family]

I've had one on my hood for several years now. It's seen rain and even snow without probs.

I'd suggest hooking up a second FP gauge. Autometer sells small ones designed to plug into the shrader valve. I've been thinking of getting one and installing a T since i hate looking back at the cowl when adjusting under the hood.

You could have a problem with your fuel system. I mean...that's what the whole point of the gauge is right?

good to know, i'm about to mount my autometer mech fp gauge on my cowl panel as well. i have 2 shrader valves under my hood; one in the normal spot on the hardline going up to the rail, and one right beside my fp regulator. i have a small one hooked up to the one by my regulator right now. good luck with your fp issue brett, hopefully it's nothing too bad

 

[jrichker]

Do this if you haven't already done it...

It helps dampen out gauge fluctuations and serves as a safety factor.

 

[cenok is family]

jrich, i've seen you post that before, and i want to do it. is that "hose adapter fitting" this guy?

autometer part # 3275

if it is, i'm assuming i drill into the NPT side, not the AN side right?

 

[Foxfan88]

thanks jrichker!!

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

 

[Black1987Stang]

and also are your gauges the liquid filled kinds? If not they should help dampen out some of the variations, that's why the did it from what I know of.

And the BBK fuel pressure regulators have a port built into them to tap in a fuel pressure gauge....orrrr you can put on a sn 94-95 fuel rail which has two spots to tap into for a gauge and it flows more than fox rails to boot....skinny round fox rails compared to the nice thicker square sn95 rails and they drop right in you just need to bend one line a little make it fit.

 

[Foxfan88]

the gauges arent liquid filled.

 

[jrichker]

jrich, i've seen you post that before, and i want to do it. is that "hose adapter fitting" this guy?

autometer part # 3275

if it is, i'm assuming i drill into the NPT side, not the AN side right?

That is the correct fitting.

I would do the pipe side simply because it prevents any damage to the machined AN flare.
In reality, it doesn't matter.

 

[Foxfan88]

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