ahusted

Just a quick question, I have a liquid filled fuel pressure gauge that leaked out. I have another on order but was curious if the liquid affected the accuracy of the gauge or just helped supress needle movement from viberation? I would like to get some pressure readings before friday when the new gauge gets here, but I don't want to make adjustments if the accuracy of the gauge is not good.
Any thoughts?

Streetiron85

I had a liquid filled one and I purposely drained the liquid, cause it was causing erroneous readings.
The liquid is effected by the underhood temp changes that offset the press in the fuel line causing a false reading.
I'm not the only one who has had this problem.

SScott

That is a good question. I never thunk it.

Streetiron85

Yeah, it's happened to a few guys with liquid filled gauges.
Drain the liquid out and suddenly the gauge works the way it should.
Simplest thing in the world to fix.

ahusted

Thanks!! I'll try it tonight!
My old gauge is a 15pound gauge (TBI) and I bought a new 30 pound gauge. Wish I had known.... I would have gotten the unfilled one.
What is the reason for the filled gauges then?

Streetiron85

I ast the guy at the parts store the same question.
And he told me he didn't know why they even make them, cause everyone has problems with them.
Someone at one time thought it would be cool to make an oil filled gauge, he said.
I think they keep making them because guys who don't know any better keep buying them.
But it's such an easy problem to fix that no one's ever bothered to complain about it.

It kind of reminds me of going "snipe hunting"
Or that "trick soap" that they sell at the joke store that turns your face black.
It's some harmless part of the initiation process that you only sucker for once.

Guys buy them, and they keep selling them.

ahusted

Hmmmmm..... Well my gauge is deader than a door nail now that the fluid leaked out.
Guess I'll have to wait for my new gauge from Summit to show up.

IHI

iTrader: (1)

Liquid filled guages are used almost exclusively in the heavy equipment trade and the answer was already give above as to why-to limit/supress needle fluctuation/bouncing when the machine is running.

Regardless, I've run both and different brands of both filled/non filler and will tell you either way they are affected by under hood temps...it wont be long and you'll see for yourself

Only true way to get an accurate reading getting it away from the heat weather it be mounting under a cowl, using an isolater and in cab mounting, etc...right near the carb and it will start to vary.

ahusted

So should it still operate in some capacity if the fluid leaks out?

I don't leave this gauge mounted all the time, I just splice it in for fuel checks and adjustments.(TBI Truck) I changed the fuel pump, found a factory kinked rubber line and wanted to confirm 13 psi at idle 15 psi with no vac signal.(vafpr)

The needle doesn't move at all... And the truck runs and drives so the gauge must be dead.

I'm not sure how they work exactly, diaphram like a regulator, moves the needle?

I've got a new one coming in tomorrow, I was just hoping to finish up tonight.

Streetiron85

Maybe the daiphrgm on yours broke and the fluid leaked out through the hole in the diaphragm.
Mine had a little rubber plug in it that I just popped out and I left the hole open so there would be atmospheric pressure within the casing, and it shows consistent readings whenever I've looked at it.
If you're only using it occasionally as you described, then there wouldn't be any underhood temp variable effecting it anyway.