Planning to instrument my truck, I've arrived at the decision of mechanical versus electric for the fuel pressure gauge. I'm leaning towards electric for safety reasons. I might yet be persuaded to choose a mechanical gauge, if someone can answer me this:

What prevents the diaphragm in a fuel pressure isolator from failing and allowing fuel to flow through?

 

Given time, anything can fail.

I prefer the electric gauges. Old days, I would agree with the mechanical gauge choice. With today's electrical systems and gauge design, the electric gauges are MUCH more accurate, reliable, and less susceptible to voltage variations.

I have the NV series; but don't care for the backlight. It's too bright at night. Any of the 270 degree sweep autometer 2-1/8" diameter electric gauges will give you the accuracy in an electric gauge you are looking for.

Tony

 

I have never seen an isolator allowing fuel into the cab, but I have seen them fail (a fair amount actually). I have a mechanical gauge plumbed straight to the gauge with a needle valve, and no isolator. Dependable as can be.
mishkaya

 

Nothing.
I've only taken six apart but four of them had failed and let fuel though.
One was only a couple weeks old. Isolators are waste of money, just an expensive coupling and cause bad readings to boot.
No problems with electric senders on 24 valves but on 12s they don't last and start lying to you.
What good is a gauge you can't trust?
I've had mechanical gauges in both my rigs for over ten years without a single problem.
I use a needle valve barely cracked open at he head of the gauge line to dampen pulsations from the 12 valve's mechanical pump that causes the needle to swing so wildly that you can't read it in the short time before the gauge self destructs.
With the needle valve barely open any leak would be a slow drip into the cab.
Even if it did leak all you would have to do is shut the valve.
Think a needle valve is a good idea even on a 24 valve.

 

I think that's what kills the isolators. They need a snubber for protection as well as the gage.

 

Agree with the usefulness of a isolator. I rarely hear of one working well or lasting long.

I have been running diesel straight into the cab for years now.

 

When yall bought your FP gauges did you just buy the gauge, some tubing and a needle valve or the whole kit and just add a needle valve. The kits like $130 but the gauge itself is under $50.

 

If the kit is that expensive, it most likely comes with the isolator, which you don't need. In that case just get the gauge, and go to your hardware store to get the plumbing you need to hook it up.
mishkaya

 

Had my isolator on for over 3 years and no issues, knock on wood.

 

A snubber performs exactly the same function as a barely cracked open valve.

I've heard a lot of people say that but wonder how they know.
Only real way to tell is to disconnect the line to the gauge with the engine running. Not something most folks would do.