Fuel pressure, sensor

[designrs]

bstrachan, You problem sounds sporadic, as in momentary glitches, perhaps electrical. My problem is of a longer duration as is a progression of indicated fuel pressure loss... 3.0, 2.8, 2.5, 2.1, etc. and in most cases responds to throttle adjustment.

If it happens at cruise, it is remedied by throttle adjustment.
If it happens on taxi, it is remedied by turning on the electric pump.

Still, it could be electrical. It could even be in my Dynon.
Sigh... trouble shooting is a PITA!

P.S. bstrachan, I see that you are from Cedar City, UT. I'm going to PM you for some local pilot info, if I may please?

[designrs]

Flew tonight near sunset. Coolest weather yet, just 70 on the ground. Had a low fuel pressure warning just when turning onto the runway for departure, boost pump already on. I watched it normalize immediately on take-off roll. Completely normal flight.

As noted before, sender was replaced.
Now strongly thinking that this is electrical and/or a Dynon issue.

[designrs]

I think this is it! Here's a guy with a Dynon that has the EXACT same problem I do... even after two VDO fuel pressure senders. His solution was to install Kalvco sender from Dynon. They come in three pressure ranges which better fit the motor.

http://dynonavionics.com/cgi-bin/yabb2/ ... 972434/0#0

This guy had a Lycoming in an RV-6 with SkyView.
I'm Rotax with the Dynon D-120...
but the problem matches exactly.
Hopefully the solution will also.

Contacting Dynon now...

[3Dreaming]

Was talking with a friend who retired from the fuel pump manufacturing business. He stated that if the drain hose on the new Rotax fuel pump becomes plugged or pressured up, that it will not be able to pump fuel. It might be worth while to inspect the vent line installation for a possible problem.

[designrs]

Vent line is good... AND it's not supposed to be hanging out of the cowling... but rather clipped at least 12 inches back inside.

[3Dreaming]

Vent line is good... AND it's not supposed to be hanging out of the cowling... but rather clipped at least 12 inches back inside.

I'm just trying to be helpful, no need to get angree. I didnt suggest that it should be hanging out the cowling. I have installed several of the new pumps, and am quite familiar the Rotax SB regarding installation of the vent hose.

I was think more along the lines of the vent hose having a bad spot inside, being pinched somewhere, or having something that is partially plugging the hose.

[designrs]

Not angry at all. Hope it doesn't read that way! I appreciate the help.
The part about clipping the hose was stressed because it is a very critical point that some might not be aware.

Very appropriately, I checked the drain/vent line off the mechanical fuel pump today and it was on kinked. It could very well be the reason.
Thank you!

[drseti]

Not angry at all. Hope it doesn't read that way! I appreciate the help.

One of the problems with forum communications is that they don't convey emotion. Without such nonverbal cues as smiles and a twinkle in the eyes, it's hard to know the intent behind the words. My wonderful wife Muriel has a great cure for that - whenever the intent of the poster is unclear, she always assumes the best rather than the worst.

[drseti]

I checked the drain/vent line off the mechanical fuel pump today and it was on kinked.

Did I put that pump on your plane, Richard? If so, mea culpa!

[designrs]

Well, it was good to replace the kinked drain / vent hose. I really thought that it was the "smoking gun". Unfortunately that was not the solution either.

Now ordering the new Kavlico pressure sender from Dynon which will require a firmwear upgrade to the Dynon D-120. EMS.
http://dynonstore.com/#!/Carbureted-Fue ... p/52526485

This is frustrating but hopefully getting close to a solution.

[drseti]

I have one of those Kavlicos in stock, Richard. In addition to updating the EMS to the latest firmware, it requires that you wire it into a 5 volt source (the VDO sensors did not require external power). Dynon has an installation guide describing the requirements:

http://dynonavionics.com/downloads/Inst ... -Rev_B.pdf

[designrs]

Interesting Note: The new Kavlico 15psi sensor will show a minimum pressure of 1.2 psi. So even if your fuel pressure were ZERO you would still see 1.2 psi on the Dynon. Also it requires a 5 volt connection to the Dynon bus.

[designrs]

New Kavlico fuel pressure sender arrives tomorrow from Dynon.

Meanwhile two interesting scenarios, both on cool early evenings:

Flight 1: Low Fuel Pressure alert upon entering runway for takeoff. As soon as I hit the throttle fuel pressure popped up. Continued takeoff. Flight completely normal. No alerts.

Flight 2: Low Fuel Pressure alert on full power for takeoff... continued falling to 2.0 psi. Aborted takeoff. Grounded plane until further inspection.

Now two options:

Option 1: Attach a manual fuel pressure gauge. Taxi around. Do a full-throttle aborted takeoff, and try to duplicate the problem. (This would be a definite indicator of mechanical or electronic problem.)

Option 2: Upgrade to new Kavlico sender, different configuration requiring some wiring and firmware upgrade. (Suspecting electronic. I'd still do the ground tests. If problem persists then I just have to do the mechanical gauge.)

I think option one is the right thing to do first... yet I'm optimistic about option 2 solving my problem.

What would you do first?

[MrMorden]

I hope this gets you running with no further problems!

I guess on the bright side, you have determined it's a sensor issue and not an "OMG my engine could quit any minute" issue.

[dstclair]

Is your FP sensor located on the firewall or hanging off the fuel pump?