[GMCnet] Mechanical Fuel Pressure Gauges are OK in the Cockpit

[tomk...@comcast.net]

Guys,

In researching my recent installation issues with the Howell EFI, I found many who warned of mechanical gauges in the driving station. I thought I
would share something which may be over looked.

Any pressure gauge is acceptable in the dash. If using a mechanical gauge in the dash you must simply install an isolator just outside the cockpit.
This will allow you to use all styles and sizes of pressure gauges

The isolator is simply where the fuel stops at a diaphragm and a non-flammable fluid pick up. I prefer a silicone base hydraulic fluid. On one side of
the diaphragm is fuel under pressure and the other side is a nonflammable fluid which transfers the pressure through the diaphragm to the pressure
gauge. Any rupture in the gauge or line within the vehicle will only yield nonflammable fluid.

Not much advise, but I thought it might be something helpful for someone who likes to monitor fuel pressure on their EFI and thinks that an electrical
sender is the only option.

Take care all,
Tom K.
--
Tom & Oki Katzenberger,
Kingsville, Maryland,
1977 23' Birchaven, 455 C.I.D.
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[John Wright]

NEVER, NEVER, NEVER, NEVER, NEVER RUN A MECHANICAL FUEL GAUGE INTO THE
COCKPIT OF YOUR COACH!!!!!!!

THAT IS THE SUREST WAY TO BURN YOUR COACH TO THE GROUND!!

I will stop shouting now! Who ever told you that is a FOOL! I have built
and raced performance cars since the middle 1960's. I can tell you from
past experience That a number of persons have lost their investment to a
fire. If you want to see the fuel pressure use and electric unit. In theh
earlier days we used to mount the mechanical gauge out on the cowling just
in front of the windshield and you would still have fires. Jim H what do
you think??

J.R. Wright
GMC Great Laker
GMCGL Tech Editor
GMC Eastern States
GMCMHI
TZE Zone Restorations
78 Buskirk Custom 29.5' Stretch
75 Avion (Under going Frame up Restoration)

[James Hupy]

I agree 100 %. Had a fuel fire in a race car once. That was plenty. Thank
God for fire suits, gauntlets, respirators, I only got some scorching above
my respirator, and just a bit on my wrist. Fire was out when the car came
to a stop.
Worst thing that can happen to a motor home, too. Really, do you need
to know that info badly enough to lose a coach over? When you are tuning
and setting up the fuel injection, hook up a temporary gage to verify what
you need to know, then remove it.
It is a really sad day when you come back to a burned coach and find
it all covered with dry chemical extinguisher chemicals and realize how
much of a challenge it will be to get back to where you started from. Makes
a grown man cry, for sure.
Gasoline fires are nothing to fool with. Please do not introduce
hazards where none existed previously.
Jim Hupy
Salem, Oregon

[tomk...@comcast.net]

J.R. and Jim,

With an isolator there is no fuel in the cockpit. From the isolator on to the gauge is antifreeze or silicone fluid. There was a time when fuel
pressure gauges were only mounted on the hood. Those days have past.

I don't know how there can be a fire without flammable fluids. It might be worth reading up about fuel pressure isolators. This is the sole purpose
they were developed.


Just a quick cut and past from the web:
"Mechanical is the best and most accurate. If installed correctly with a fuel pressure Isolator fuel will never enter passed the firewall.These
isolators are designed for mounting of any mechanical pressure gauge inside your ride. They're rated at 200 psi working pressure with a maximum of 300
psi peak, and are compatible with gasoline, oil, and antifreeze. How it works. Fuel travels from your fuel rail to your isolator via a braided hose
then the isolator transfers the pressure to your interior mounted guage via a nylon hose filled with antifreeze/water etc.. thus leaving the danger
outside your driving compartment."

I think it may be beneficial to look at this technology.

[Ken Henderson]

Not only do I agree with John & Jim about mechanical gauges in the cockpit,
I argue against one within the engine compartment. When first installing
EFI on the GMC I didn't have an electronic gauge available so I mounted a
mechanical one at the rear of the engine compartment, under the hatch
cover. It was plumbed before the regulator so displayed very erratic
readings. Within a short time, the needle had been shaken off of its
shaft. I replaced it with another (both were from reputable
manufacturers). Not too long after that, I was still getting some
readings, but I noticed gas odor: that second gauge's bourdon tube had
ruptured and gasoline was falling drop by drop onto the engine and running
over the exhaust manifold. I've no idea why it didn't ignite -- it should
have! No more analog/mechanical fuel gauges for me ever! The electrical
ones don't cost much and are far more reliable.

Ken H.

[James Hupy]

My fuel fire was caused from a fuel pressure regulator that failed, sprayed
fuel under pressure on a hot engine. Not fun when you are strapped in. Had
a good MANDATORY fuel shut off upstream from the pump. Saved my butt.
I agree that isolated gages are an improvement over live fuel ones.
But, every connection is a potential failure. If I had my 'druthers, I
would vote for the fewest distractions to the driver.
Jim Hupy
Salem, Oregon

[D C _Mac_ Macdonald]

Local (OKC, OK) GMCer had similarly caused fire in
his GMC. Luckily went out before major damage.

D C "Mac" Macdonald
Amateur Radio - K2GKK
Since 30 Novemb'53
USAF and FAA, Ret'd
Member GMCMI and Classics
Oklahoma City, OK
"The Money Pit"
TZE166V101966
'76 ex-Palm Beach
k2gkk + hotmail dot com
wwww.gmcmhphotos.com/okclb

________________________________
From: James Hupy <james...@gmail.com>
Sent: Sunday, December 12, 2021 16:27
To: gmc...@list.gmcnet.org <gmc...@list.gmcnet.org>
Subject: [GMCnet] Re: Mechanical Fuel Pressure Gauges are OK in the Cockpit

My fuel fire was caused from a fuel pressure regulator that failed, sprayed
fuel under pressure on a hot engine. Not fun when you are strapped in. Had
a good MANDATORY fuel shut off upstream from the pump. Saved my butt.
I agree that isolated gages are an improvement over live fuel ones.
But, every connection is a potential failure. If I had my 'druthers, I
would vote for the fewest distractions to the driver.
Jim Hupy
Salem, Oregon

[tomk...@comcast.net]

Jim and Ken,

I agree that the fewer connections the better.

I am not sure that an electric sender is any safer then an isolator. The isolator does not carry current or flammable fluid and both the sender and
isolator are inert going from the fuel line to the cab.

For sure having nothing is safer than either the sender or isolator. I like that I know immediately when a pump fails or is going to fail. Some pumps
have a tendency to fluctuate prior to failure and that may be enough to get you to a safe location for a planned change out.

Very good points on all ends. For sure if you are going to have gauge have an isolator or sender.

Stay healthy,

[Bill Van Vlack]

You can wire an electrical fuel pressure gauge into one of the analog ports on the EBL and run datalogs to analyze it. Use WinLog-EBL to sound an
audible alarm, run a separate datalog, and/or display a gauge for real time diagnostics. Unless you're driving or have a co-pilot/monitor of course.

--
Bill Van Vlack
'76 Royale; Guemes Island, Washington; Twin bed, full (DS) side bath, Brazilian Redwood counter and settee tops,455, 6KW generator; new owner a/o mid
November 2015.

[tomk...@comcast.net]

Bill,

That is also another good solution for those who wish to monitor the fuel pressure. You would still have a sender or isolator.

Both the isolator and the sender have a diaphragm. It is just the isolator has no electric and there for no possibility of spark.

I have flown military and civilian aircraft, fixed wing and rotary wing, in all of them, including my current bush plane, I have and had a fuel
pressure gauge factory installed and FAA approved.

It appears to be like anything else, personal preference. One must respect each persons beliefs.

Jim H. is correct in that removing the gauge from the equation moves the potential for failure to zero. Maybe in the air the engine is a little more
important. LOL.

Take care,

[John R. Lebetski]

What if the isolator diaphragm fails and it is sending fuel into the cockpit, but you don’t know it as gauge looks fine.
--
John Lebetski
Woodstock, IL
77 Eleganza II

[Mike Hamm via Gmclist]

seems to me the gauge would have also go bad to be a problem.

Better chance af getting hit by lightning and going to heaven.

JohnL455 wrote on Sun, 12 December 2021 21:36

> What if the isolator diaphragm fails and it is sending fuel into the cockpit, but you don’t know it as gauge looks fine.


--

1977 Kingsley 455 as stock as it gets except lots of Ragusa parts

[Keith V]

The point of the isolator is mostly to eliminate the fuel line into the cockpit. That fuel line, if most often the failure point IIRC, not the diaphragm., same issue with oil pressure
________________________________
From: Mike Hamm via Gmclist <gmc...@list.gmcnet.org>
Sent: Monday, December 13, 2021 12:41 AM
To: gmc...@list.gmcnet.org <gmc...@list.gmcnet.org>
Cc: Mike Hamm <mgh...@verizon.net>

Subject: [GMCnet] Re: Mechanical Fuel Pressure Gauges are OK in the Cockpit

[Jim Kanomata]

There are lot of good fuel pressure senders that are available and gauges
that have the smaller range that read well.

--
Jim Kanomata ASE
Applied/GMC, Newark,CA
ji...@appliedairfilters.com
http://www.gmcrvparts.com
1-800-752-7502

[tomk...@comcast.net]

John brought up a good question for which I had no answer, so I called "AutoMeter" the manufacturer of the Isolator which I am using.

I spoke to a gentleman by the name, Doug and he stated that John is in fact correct in that if the diaphragm should suffer a tear or hole it is
possible for fuel to make it to the antifreeze/silicone line and subsequently the gauge.

Beings that the diaphragm has equal pressure on both sides and the diaphragm has very little stress, this has not presented itself as a problem. Doug
said that there is little worry of this happening. I asked him, is it possible that the operator would be un aware of the failure if it occurred and
he said yes.

The diaphragm in an electric sender is generally pressed up against a spring of some sort an may have a little more pressure differential then that of
the isolator. Also the sender failure also incorporates an electrical component.

This brings me back to Jim H. Do we really need the pressure gauge and the fact that not having one removes the possibility failure.

In over 30 years of flying aircraft, all of which had fuel pressure gauges in the dash, I have never had a fuel pressure gauge failure/fuel leak.

At this point, I can not determine what the right answer is? I am back to respecting each persons personal decision.

Sorry, as this post may have been of no help. Just more information.

Take care and stay healthy,

[James Hupy]

Agreed that aircraft are a whole different critter than a motorhome. Really
hard to just pull over to the side in flight. So the risk is justified by
the greater need for accurate information.
I read the book about the first aircraft to fly nonstop around the
world. A twin engine ultralight aircraft that was literally a flying fuel
tank. They had one fuel gage and a complicated number of tank switching
valves and pumps. They proved none too reliable in actual use, and were a
constant cause of worry to both Dick Rutan and Gena Yeager, the co-pilots.
Great book. Nothing to do with gmc's, I know, but the fuel gage in the
cockpit.
Jim Hupy
Salem, Oregon

[Matt Colie]

It is common practice to have an orifice in the first fitting in any liquid line that goes anywhere, so even if the isolator should fail, it would
take a long time for the liquids to mix and cause any trouble. People that run mechanical lube oil pressure gauges should also be aware.

Matt
--
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit

[tomk...@comcast.net]

Jim,

I have 4 fuel tanks on my aircraft and can stay aloft for 8 hours. It really isn't intended that you stay aloft, it's just that, as a bush plane it
may be 8 hours between refueling points. Fuel tank management can be a big deal and I have lost my engine because I ran a tank dry at 7,000 ft. over
Augusta Ga.

This morning I called a good friend Carlo, who is a head Mechanic at the Airplane Owners and Pilot Assoc. (AOPA) and asked him what his take on this
situation was and what are his thoughts. He is extremely experienced and has built many aircraft. He said that yes, direct plumbing to the gauge,
Isolators and Senders are all used. He mentioned some device that limits the amount of fuel that can move forward in the event of a diaphragm failure
with an isolator.

He further told me that every one building new aircraft are all going to Electric sending units and gauges. The accuracy has improved as well as
safety.

To change an aircraft design requires a lot of paper work (Form 337, STC and the like) Not so with a motorhome. With that in mind I will be adopting
Ken H's philosophy of electric Sender and Gauge. I will pull the isolator and switch to electric a little later in the build. We only have one door on
our motorhomes and our families are often on board. The only next best choice is to pull pressure gauges totally.

Thanks all for all the input.

Take care,