0.0 Fuel pressure while on cross country

[Rrhsch]

I think I need a new fuel pressure sensor. Shortly after a refueling stop with 100LL, the fuel pressure started to swing rapidly from 1.1 to 5.0 psi at 5400 RPM and suddenly stopped at 0.0 psi. Engine was running fine. I made a precautionary landing to check out the problem.

On the ground I determined that I had fuel pressure that wasn't registering on the G3X. I could hear the electric pump running and tested the flow from the gasolator to confirm the pump was indeed working.

It was very hot out and I decided to let the engine cool for a couple of hours. When I powered up the G3X the fuel pressure showed max fuel pressure 14+ psi. As soon as I started the Rotax, the fuel pressure started to swing up and down and stoped at 0.0 psi.

I unplugged the sensor, removed the rubber seal and reattached the plug with no change in the reading.

After extensive taxi testing and run-ups I finished the flight.

I will order a new sensor unless some one has had the same symptoms and resolved it using a different method.

[tomkk]

I had a similar problem. Replacing the sensor corrected mine ...

[DHeal]

Could be the sensor or the wiring. My money is on the wiring having a loose connection -- check that first, its cheaper!

[tomkk]

Originally Posted by DHeal

Could be the sensor or the wiring. My money is on the wiring having a loose connection -- check that first, its cheaper!

Good point ...

[RFSchaller]

Sometimes I think these sensors cause more problems than they solve. Over the years I’ve owned 7 aircraft and 4 had no fuel pressure indication. I never missed it, and the response to any engine stumbling always included turn on the aux pump. Never needed it either fortunately!

[chrispratt]

Check the ground wire and surface its attached to. So many of my problems early in flying my airplane were poor grounding.

Chris

[rvbuilder2002]

Originally Posted by RFSchaller

Sometimes I think these sensors cause more problems than they solve. Over the years I’ve owned 7 aircraft and 4 had no fuel pressure indication. I never missed it, and the response to any engine stumbling always included turn on the aux pump. Never needed it either fortunately!

If you have a gravity fed fuel system no pressure gauge is required.
If it is not a gravity fed system, a gauge is required.

[RFSchaller]

Scott,

I am not familiar with any requirement for a fuel pressure gage unlike the minimum FAR required instruments. If you are saying it is good practice I would agree, but let’s face it if your fuel pressure really is low the engine will tell you, and if you have a back up pump you will turn it on.

On my 12 I switch the electric pump off after climb out. That does not result in a low fuel pressure alarm, so what difference does the indication make in the response? My point is that it’s nice when it works, but it really doesn’t add any value.

Rich

[Piper J3]

Originally Posted by RFSchaller

Scott,

I am not familiar with any requirement for a fuel pressure gage unlike the minimum FAR required instruments. If you are saying it is good practice I would agree, but let’s face it if your fuel pressure really is low the engine will tell you, and if you have a back up pump you will turn it on.

On my 12 I switch the electric pump off after climb out. That does not result in a low fuel pressure alarm, so what difference does the indication make in the response? My point is that it’s nice when it works, but it really doesn’t add any value.

Rich

Well, I guess you could carry that logic a little further and say the engine will tell you it looses oil pressure when it seizes up or no engine noise might mean you have exhausted your supply of fuel.

If for no other reason, the fuel pressure gage is necessary to verify that both fuel pumps are running while performing a pre-takeoff check (you do a pre-flight check?). With master switch on, and engine not yet running, the fuel pressure should be ~ 2psig. With engine running the fuel pressure increases to ~ 5psig signifying that both electric and engine driven pumps are both working and it is safe to proceed.

It’s really hard to believe that anyone would advocate that a fuel pressure gage doesn’t add any value. I never thought I'd have to defend the necessity of having fuel pressure displayed for safe operation of an airplane. Maybe its like Trumped-up Government where you just get rid of everything and fly by the seat of your pants...

[rvbuilder2002]

Originally Posted by rvbuilder2002

If you have a gravity fed fuel system no pressure gauge is required.
If it is not a gravity fed system, a gauge is required.

Originally Posted by RFSchaller

Scott,

I am not familiar with any requirement for a fuel pressure gage unlike the minimum FAR required instruments. If you are saying it is good practice I would agree, but let’s face it if your fuel pressure really is low the engine will tell you, and if you have a back up pump you will turn it on.

On my 12 I switch the electric pump off after climb out. That does not result in a low fuel pressure alarm, so what difference does the indication make in the response? My point is that it’s nice when it works, but it really doesn’t add any value.

Rich

Bad choice of a word without clarification.
I did not mean that FAR 91 requires it..... common sense (which established it as standard practice) requires it.

A carburated engine will easily run on only .5 psi pressure.
No pilot would takeoff with a pressure gauge indicating only .5 psi.
Short of an indication failure, it shows that there is something wrong in the fuel delivery system, but if there was no pressure gauge, the engine would have started fine but that in it self doesn't assure that the flight will end well......

That means a lot of added value in my opinion.