Anyone had problems with liquid filled fuel pressure gauges in the heat (ex. Summit)

[dville_gt]

I have been chasing my tail with this fuel pressure dropping off after the car gets hot (mostly happening when the car gets hot and I park it, then restart it hot). Started wondering if it could be air in the line from the reg to the gauge in the cowl area since my pump has no check valve, but that led to a few post I found about these liquid filled gauges being pieces of shit and reading low (or zero) when they get hot. Something about the gauge compares line pressure to atmospheric and since they are internally sealed as they get hotter the pressure inside the gauge it self increases thus lowering the pressure reading shown on the gauge.

This would seem to make a lot of sense in my application sense the car doesn't seem to run differently when the gauge is reading sometimes as low as 20psi (vs. 43 base), and typically will get better after a few minutes of driving after a hot restart (probably the gauge cooling off a little from the heat soak of sitting in the cowl with no air flow).

Anyone else had a problem with this? I am thinking about just pulling the little plug and letting the liquid bullshit flow out. Upside is this is the cheapest fix I can think of!

Here is a video of a guy putting a heat gun on his gauge (granted it is a carb'd application so the fuel pressure is much lower anyway).

[NoClassic]

I had one on my old car and it never gave me any issues. It may have not been the same brand as yours though. I cant recall.

You could always grab one of the diagnostic fuel pressure gauges if you didnt want to damage the existing part. This would require installing some kind of test port of course.

Have you pulled the pump apart yet?

[dville_gt]

I had one on my old car and it never gave me any issues. It may have not been the same brand as yours though. I cant recall.

You could always grab one of the diagnostic fuel pressure gauges if you didnt want to damage the existing part. This would require installing some kind of test port of course.

Have you pulled the pump apart yet?

No, pulled the pre/post filters off and cleaned them. Rerouted some lines that were most susceptible to heat, and installed the speed controller and still got the same result.

For example.

Started it up today from dead cold in the garage. Fuel pressure was normal. Drove it up to Firestone (had a weight on one of my front runners come off). Restarted it 10 min later after they finished and the pressure was low (should be ~37psi at idle, was around 30psi per gauge. About 10 minutes into the drive the pressure was back up to ~37psi and stayed there for the rest of the trip (another 20-30 minutes).

Got home. Killed it, waited ~5 min, restarted it and pressure was ~25psi.

Seems like either the gauge is getting heat soaked or the pump doesn't like being restarted hot. Unfortunately I don't have an easy way to use my diagnostic fuel pressure gauge on this car since it hooks to the schrader and all I have on this is the 1/8th NPT on the side of the regulator.

["MrEd"]

Yes.
I have installed more than 4 of them(summit)and 1 FAST liquid filled gauges, they all seem to leak down.
Would make more sense to buy a real gauge (autometer) and either mount it outside or under the hood(don't see the point under the hood)
Your fuel issue seems to me it might be pump related.
I had a similar issue and it was a bad ground,only acted up only when it got to operating temp. (not sure why)
But my pump would not come on sometimes,I ended up running some grounds to complete a good heavy ground circuit.

[LS1Goat]

No problems with my jegs liquid gauge, but this is quite common for filled gauges. I would just switch over to a autometer gauge and dampen it if you don't like the bounce. Will be more accurate and not be problematic when hot.



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[Sleeper]

Ive had autometer fuel pressure gauges go bad as well.

[dville_gt]

I'm going to drain mine and just see what it does. I plan to replace it if it fixes it anyway with a nicer (non liquid) unit.

[jyro]

all liquid filled gauges change from temperature

Their all bourdon tube actuated and the tube is ambient pressure sensitive. The plug at the top of the gauge is removable to equalize the pressure inside the gauge.
get a electric gauge and mount it inside like the pro cars do

http://www.autometer.com/cat_gaugedetail.aspx?gid=3941&sid=76

http://www.autometer.com/download_instruction/191y.pdf

[JETFAST]

they are all junk. with liquid fill they have there own atmospheric pressure. they all read wrong. use a real gauge and you will not have such problems with accuracy's.

[white88]

The only issue I've ever had with them is they'll leak out the fluid after a while, causing the needle to jump all over the place and can't get an accurate reading.