Fuel Pressure Alarm

[N751JM]

Has anyone with a "late model" CTLS experienced a low fuel pressure alarm (red engine alarm light, pressure dropping below 1.8, sweet voice announcing "fuel pressure") during a takeoff climb? I am able to get this consistently during a stop & go with a Vx climb in the go. The engine continues running fine, but the pressure drops to about 1.6. Fuel pump and fuel pressure sensor have both been replaced, but the alarm still occures under the conditions described.

 

Can anyone duplicate this?

[chanik]

All the time when it is hot outside. Seems the sender on top of the engine gets bubbles so it reads way up and down. flying level for awhile clears it. Never happens when OAT is below 80F for me

[Roger Lee]

Yes and I see it frequently.

The fuel pressure hose hangs down from the top of the engine to the bottom down by the battery. This fuel never gets refreshed. It gets old and stale from sitting and going through many heating and cooling cycles. Then it starts to clog up the tiny orifice in the fuel pressure sender. Just unscrew the sender and take a can of carb cleaner with the little red plastic nozzle. Hold that nozzle up against the hole and give it a 1 second squirt. Do this 4-5 times. It should work fine after that.

If not then throw it away and put a new one on.

 

http://www.egauges.com/vdo_indS.asp?Sender=30PSI&PN=360-043

 

I relocated mine back in 2008 on the fire wall above the engine level. It has performed flawless since.

[Flying C Farms]

Since I relocated mine four or five years ago, have not had any problem.

[N751JM]

Ok, thanks for the feedback. Seems like the original location is not the best from a design perspective. Is any authorization from Flight Design required to move the fuel pressure sensor?

[WmInce]

. . . "I get Fuel Pressure warning regularly in the new CTLSi. Means nothing. The light and the warning happen once just before runnup usually, sometimes on first takeoff." . . .

 

Means nothing?

Why not?

If the warning system is installed, shouldn't it work reliably? Otherwise, why have it?

 

Whatever.

[Roger Lee]

I don't know where CTLSi's upper and lower fuel pressure limit is set on the Dynon, but it could need adjusting. I can get a low pressure after I fly out for breakfast and come back about 45 min later and see the fuel pressure low until I run the plane a few minutes at about 2300 rpm to get some cooler fuel in the system then it comes right back.

[FastEddieB]

1) Routinely ignoring or dismissing warning lights is not a good idea. They may really be trying to tell you something.

 

2) I did relocate the fuel pressure sender on my Sky Arrow from an engine baffle to an off-engine site. This after the original gradually showed less and less pressure.

 

3) Don't know how common this is, but when turning off my boost pump, the fuel pressure often drops to about zero on the gauge for a couple seconds before climbing back up into the green. Has pretty much always done this. Don't think I've ever gotten a good explanation why. I don't have any low fuel pressure light or alarm, but I imagine if I did this behavior would set it off.

[Doug G.]

Unlike "he who shall not be named," I will continue to pay attention to the warning lights and sight tubes on my plane.

[Roger Lee]

You should pay attention to lights and low pressures, but you should know when it's a false indication by cross referencing other readings, the way the plane acts and by getting more educated on senders and their common issues.

If my fuel pressure dropped to zero and the plane kept flying at full rpm and never sputtered then I wouldn't get overly worked up and land on the nearest road, but continue on and check it at the next airport or earliest convenience. I get calls all week long on funny reading from senders. Most of the time it's the sender and sometimes like the new Rotax fuel pump the old alarm settings are wrong and need new alarm limit set points. As an example: If you have a new Rotax fuel pump the new max limit isn't 5.8 psi any more it is 7.2 psi. A new max limit in the Dynon should be set or if you have an analog and new visual point on that gauge.

 

Pilots years ago didn't have all this fancy digital multi information systems and they flew along without many of these information overload systems. Never bothered them. Knowing how to decipher the digital age comes in handy.

[Farmer]

I did get a fuel warning on each takeoff and landing with the CTLSi. It was an out of range over pressure at about 45, yellow caution. It was the results of the second fuel pump that is required for safety on takeoff and landing. The CTLSi will not run if there is no pump running. I rather liked the caution as it told me the second pump was functioning. I do not know how the engine start will go if the first pump fails in flight after the second has been turned off, and hope never to experience same.

 

Farmer

[FastEddieB]

I suspected it was due to the fact that I often takeoff without the Aux Pump on, the POH says to turn it on.

 

How were you instructed on it, and if told to disregard the POH, what was the rationale?

[Ed Cesnalis]

I suspected it was due to the fact that I often takeoff without the Aux Pump on, the POH says to turn it on. I am gonna start doing that.

 

Power loss on departure frequently results in fatalities. Failure to use the auxiliary pump in some aircraft can result in engine failure. Use of the aux pump in other aircraft can cause an engine failure.

 

You do not possess the skills to analyze engine problems on departure. Training on this issue needs to be correct and needs to be followed, you are now going to use the aux pump because of discussions here?

[Matt]

You should pay attention to lights and low pressures, but you should know when it's a false indication by cross referencing other readings, the way the plane acts and by getting more educated on senders and their common issues.

If my fuel pressure dropped to zero and the plane kept flying at full rpm and never sputtered then I wouldn't get overly worked up and land on the nearest road, but continue on and check it at the next airport or earliest convenience. I get calls all week long on funny reading from senders. Most of the time it's the sender and sometimes like the new Rotax fuel pump the old alarm settings are wrong and need new alarm limit set points. As an example: If you have a new Rotax fuel pump the new max limit isn't 5.8 psi any more it is 7.2 psi. A new max limit in the Dynon should be set or if you have an analog and new visual point on that gauge.

 

Pilots years ago didn't have all this fancy digital multi information systems and they flew along without many of these information overload systems. Never bothered them. Knowing how to decipher the digital age comes in handy.

Hello, I have a Dynon Skyview with 5.1 firmware as per Flight Design release. I'm not able to change the max pressure, and do get these alarms mostly on low power. Do you or does anyone know how I can get the max value changed? I'm eagerly waiting for a new Flight Design release, but none seems to be published after waiting for months. Thanks for any info.

[Roger Lee]

I don't know of any way to change the new Skyview other than just doing the update.

[Jim]

I get Fuel Pressure warning regularly in the new CTLSi. Means nothing. The light and the warning happen once just before runnup usually, sometimes on first takeoff. OAT about 60f.

 

You'll need to resolve it before your checkride. Dollars to doughnuts the DPE won't fly if it happens.

[FlyingMonkey]

You'll need to resolve it before your checkride. Dollars to doughnuts the DPE won't fly if it happens.

 

That's a good point. He might even let you run through that indication and start rolling to test your ADM, then pink slip (fail) you if you elect to continue the flight.

[FastEddieB]

You'll need to resolve it before your checkride. Dollars to doughnuts the DPE won't fly if it happens.

 

Nah.

 

Just tell him it "means nothing"!

[Ed Cesnalis]

Did it come on for your wife's checkride? If so what did the DPE think and is it the same DPE that you will use?

 

Is it malfunctioning? Low fuel pressure on take off in a FI engine sounds like a serious concern, before run-up not so much.

[FlyingMonkey]

My airplane always has perfect fuel pressure, because I don't have a gauge installed for that.

[Roger Lee]

Low or high pressure may be just where the alarm limits are set. Any where from 2.2 to 7.2 is good. It will fly full throttle quite a bit lower than 2.2. That has been tested on my plane.

[Gmoore7]

I just got my CTSW out of annual and we changed out the fuel pump with one that has a overflow drain hose. My fuel pressure is reading as high as 6.3. I flew for an hour Sunday staying in the pattern (just to be safe) and found that at idle or low RPM's the pressure was the highest. At full throttle it lowered to 4.3.

Any ideas?

[Rich]

Roger,

 

Thanks for the info on the 7.2 vs. the 5.8. I have the new pump but my high side was set at 5.8 from the dealer.

I'll make the change next time out.

 

[Roger Lee]

Hi Gary,

 

That's normal for the new pump.

[FastEddieB]

Think long and hard about operating "outside the book", picking and choosing which of the manufacturers procedures are "right".

 

If they are actually in error, they should be brought to FD's attention and they should be corrected.

 

This actually did happen in the Cirrus world - pilots found things in the POH that did not make sense and reflected upon them on a site such as this. And there were several instances of future POH revisions being modified to come into line with those recommendations.

 

If you had an accident from power failure after takeoff or on approach and the NTSB determined that you had not had the boost pump on, that would certainly be listed as a contributing factor.

 

If I were you I would bring this to FD's attention and document their response.