racerseks

I'm adding a fuel pressure gauge at the fuel rail on a mostly stock '86, but don't have any instructions. I am guessing the needle in the Schraeder valve needs to go, is that right? And...a connector was supplied for Schraeder to gauge. The part going to the rail fitting is aluminum, while the part going the the gauge is brass. Both ends are threaded, and I am wondering if I should use any type of sealant, loctite etc. Guessing I should avoid teflon tape...or maybe I don't need sealant any at all. Your thoughts and/or experience appreciated.

Cliff Harris

I you're doing something like this:



You do need to take the Schrader valve out because the gauge doesn't have a way to press down on it.

I didn't use any thread sealer or other similar gunk.

racerseks

Yes, very similar. Okay, in goes a fresh Schraeder valve, and no sealant. Glad to hear that...didn't want to risk clogging an injector or something. Thank you!

antfarmer2

No sealant needed but a touch of blue locktight would not hurt.

Joe C

on removing the Schrader valve. a nice touch is to angle the gauge 45° for better viewing.

WVZR-1

I get the determination to check fuel pressure randomly but all "under-hood" installs can be subject to multiple types of failures. Inaccuracy certainly, AIR gauges tend to fail more frequently than LIQUID FILLED and there's technology that allows bleed off of higher end LIQUID FILLED gauges that are reported to display inaccurately when the LIQUID FILL is "heated" - I don't quite get the thought that it's something that needs constant monitoring. The cap of a Schrader fuel pressure port provides a "safety seal" with an internal o-ring on nearly all "purpose built" Schrader fuel caps.

383vett

At the track between rounds, if my afr is too rich or lean as determined by my wideband readout, I can either bring out the laptop and make adjustments or take out a 1/4" wrench and loosen or tighten the fuel pressure regulator a small amount. I need to monitor the fuel pressure in order to do this. I'm not saying these gauges don't fail, but I have had the same gauge underhood for about 20 years and it still works fine.

aklim

That is interesting. On my diesel (a completely different animal), I have had 4 different gauges. Air or Liquid filled didn't make a difference. None of them lasted a year. I had them from reputable vendors and other Summit or Jegs. Finally gave up and put a Schrader valve and used a gauge whenever I needed to. In this case, it might work with less vibration and heat, IDK. I know on my 7.3 Powerstroke, I couldn't get them to last a year. YMMV

Dt86

I wouldnt put one on mine. Thats my personal preference obviously, but my reason is that they have been blamed for engine fires. Id rather not roll that dice.

racerseks

Thanks...I think I do have some of that around here in case.

racerseks

That is a nice touch...thanks.

cardo0

Go electric! Like others said the liquid filled gauges can and do lose calibration w/o temperature compensation. The little peanut gauges Summit used to send for free where terrible and belong in the trash. The "dry" gauges have to much bounce.

I bought my Stewart Warner electric gauge for a little over $100 and you can connect to the Schrader valve or plumb in in w/tubing fittings. But this way you can mount the gauge on a pod in cockpit and watch fuel pressure anytime or during any event. Stewart Warner no longer sells/markets this model but most major gauge companies do sell an 2&1/8" electric fuel pressure gauge.

It's just that the LT1 has so many fuel pressure issues it's 1 of the most helpful upgrades we can make.

mtwoolford

On another chevy, not a corvette, I used a mechanical guage. It consisted of high quality hose from the fuel line to a diaphram style transmitter mounted in the engine compartment which had fuel on one side and had a nonflammable liquid on the other side, which in turn connected to a hose leading to a guage in the cockpit.

the advantages were that connecting a hose, which simply screwed in at the engine, was easier and neater than trying to fit a guage or electrical transmitter into a somewhat cramped and limited space, the pressure was readable from inside the car, and being mechanical / hydraulic, the guage was independent of the electrical system.

cardo0

I never tried the isolated gauges but have read a lot of inaccurate readings from them due to air bubbles/pockets in the fuel/engine side line. But that is at carburetor pressures below 10psi. I believe the higher fuel pressure of EFI around 40psi would not have the same problem. I guess I would have to try one and check it's accuracy before recommending one.

As for electric gauges there is only one wire to the sensor and one wire for gauge power but sometimes a ground wire for gauge case. But the sensor wire by itself kinda looks like a dangle unless you sleeve it.

Joe C

i'm sure there is some degree of inaccuracy on these small 1.5 inch rail mounted gauges, and I seriously doubt there is any kind of factory calibration associated with a cheap, over the counter, $20 gauge. I agree, a constant monitoring of fuel pressure is not necessary, but on the other side, it really doesn't hurt anything having a gauge, so, I guess it's a wash. personally, my liquid filled gauge may or may not be accurate, but it is a fair indicator of rail pressure. do I monitor my fuel pressure daily - of course not, but I do periodically when under the hood, just in case something does change. personally, I haven't noticed any degree of pressure change do to heat soak, from under hood temperature changes. I seem to always have 37-38 psi indicated. under hood fire - ??? - maybe, but I haven't found one instance that a fire was caused by mounted fuel rail gauge. if someone can cite examples, please do so. any issues most likely would be caused by billy-bob and his back yard mechanical skills. so, instead of adding a bunch more hearsay, I thought i'd add something a little more factual...

https://www.aeromotiveinc.com/wp-con...ure-Gauges.pdf

A Peter C4

Just a question, how do you bleed off fuel pressure, when you take out schrader valve and install gauge,to release pressure to work on fuel system?

aklim

I would check it against a gauge and if it is right, log that pressure so that if it changes, you can go looking for an issue. Kinda like your bathroom scale reads 10 pounds over consistently. Soon as it moves off the reading you are used to, go find a more accurate gauge.

I have had gauges from Autometer, Summit, Jegs and maybe aeromotive. While they have mulfunctioned and maybe read 0 psi when the truck is running, it has never sprayed fuel around so I suspect you are right.

I changed the Powerstroke from the "dead head" system to something else better but I wanted to monitor it for a while to feel good hence the gauge. All of them died sooner or later. That said, if I really wanted to monitor fuel pressure, I'd install an electronic gauge to see what it is when running to see if it is keeping up at WOT. However, as you alluded to, it really isn't necessary.

aklim

Why? If you leave it for a couple days, it should be depressurized enough for you to put a rag around it. Take rag away and air for a bit and you are done.

That said, if I want to do it immediately after shutdown, I would pull the fuel pump fuse while it was running and watch it die. No fuel, no pressure, no engine running.

Another way is to take the cap off the schrader valve and push it like you deflate a tire.