Failed Aux Fuel Pump (Facet)?

H. Paul Shuch is a Light Sport Repairman with Maintenance ratings for airplanes, gliders, weight shift control, and powered parachutes, as well as an independent Rotax Maintenance Technician at the Heavy Maintenance level. He holds a PhD in Air Transportation Engineering from the University of California, and serves as Director of Maintenance for AvSport of Lock Haven.

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dstclair
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Failed Aux Fuel Pump (Facet)?

Postby dstclair » Sat Oct 28, 2017 5:00 pm

What would be the symptoms of a failed aux pump?

I went flying today and as part of the normal start routine, fired up the aux pump just before turning the ignition. The aux pump made the normal sounds as it pressurized the system then it seemed to stop abruptly vs. slowly getting quieter as the pressure builds. I didn't think anything about it. Took off normally with aux pump on and engine ran fine. I decided to check the pump in in level flight. Turning the aux pump on usually added around 0.5psi to the system so I expected a drop when I turned it off. This time the pressure stayed constant when I turned it off. Also, no pressure was added when I turned it on. I tried this several times in level flight on the aux pump did not seem to make a difference.

I landed shortly thereafter and checked the aux pump on the ground with the engine stopped. When standing by the open cowl, I could hear the soft whir of the aux pump so it's getting power.

My aux pump has around 500 hrs on it. Thoughts?

I may just order a replacement as they are only $40. Which Facet pump should I get -- Facet 40105 (3 - 4.5psi) or 40106 ( 4 - 7psi)? Both are approved for my plane. I would assume the 40106 since the 'new' Rotax mechanical pump has a max psi of 7.26 psi.

dave
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Re: Failed Aux Fuel Pump (Facet)?

Postby Warmi » Sat Oct 28, 2017 5:08 pm

No advice on the pump but I thought , on stings, taking off with the aux pump on not advisable.
POH says “
Operation of both the engine driven and the auxiliary fuel pump for take-off and landing is not recommended. The combined pump output has been observed to overcome the carburetor float valve fuel cutoff, flooding the carburetor, preventing full power engine operation or cause engine failure.
Flying Sting S4 ( N184WA ) out of Illinois

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dstclair
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Re: Failed Aux Fuel Pump (Facet)?

Postby dstclair » Sat Oct 28, 2017 5:16 pm

That was changed with Notice 10315 (October 2015) with the 'new' Rotax pump:

Salient section:
1.8 CORRECTIVE ACTION: All TL-2000 aircraft operators are now being directed to
operate the installed aircraft electrical aux pump during takeoff, climb, all landing pattern
operations and any phase of flight in which high pitch angles may occur.
dave

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Re: Failed Aux Fuel Pump (Facet)?

Postby Warmi » Sat Oct 28, 2017 5:24 pm

Ok. Makes sense.
I am just finishing my 5 year rubber replacement so I guess I will have to re-adjust my take off/landing habits.

Btw I curious how much you guys are paying for your 5 years rubber replacement- I am personally looking at 3-4 k :(
Flying Sting S4 ( N184WA ) out of Illinois

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Re: Failed Aux Fuel Pump (Facet)?

Postby 3Dreaming » Sat Oct 28, 2017 7:15 pm

Piper has been using a similar pump for years. The behavior you describe sounds normal to me. If the output pressure of the auxiliary pump is less than the engine driven pump I wouldn't expect to see a change on the gauge.

If I was worried about it I would pull the float bowls and empty them out, then re-install them. Now turn on the pump on and check to see if the pump is running. Does it build pressure? Does it fill the float bowls fill back up? If the answer is yes I think you are okay.

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Re: Failed Aux Fuel Pump (Facet)?

Postby dstclair » Mon Oct 30, 2017 9:57 am

Thanks. I was basing my conclusion on fuel pressure behavior not being the consistent with the use of the aux pump in prior flights. I'll take a closer look later this week.

Question on the aux pump ratings. What do the upper and lower pressure ratings mean -- for instance the 40106 has a lower rating of 4.0 and an upper limit of 7.0?
dave

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Re: Failed Aux Fuel Pump (Facet)?

Postby 3Dreaming » Mon Oct 30, 2017 11:19 am

That they will supply a pressure within that range.

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Re: Failed Aux Fuel Pump (Facet)?

Postby drseti » Tue Oct 31, 2017 9:00 pm

3Dreaming wrote:That they will supply a pressure within that range.


I'd add one word, and say they will supply a pressure somewhere within that range. (Exactly where is anybody's guess.)
The opinions posted are those of one CFI, and do not necessarily represent the FAA or its lawyers.
Prof. H. Paul Shuch, Ph.D., CFII, LSRM-A/GL/WS/PPC, iRMT
AvSport of Lock Haven
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Re: Failed Aux Fuel Pump (Facet)?

Postby dstclair » Thu Nov 02, 2017 5:08 pm

False Alarm -- checked the aux pump today and it clearly is working since pressure was able to build to a stable 5.0 psi on the ground. Of course, the pump is only rated to 4.5 psi ....... :wink:
dave

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Re: Failed Aux Fuel Pump (Facet)?

Postby drdehave » Sat Nov 11, 2017 1:17 pm

I had to replace the Facet electrical pump on my 2007 Sting a few months ago. The first indications were intermittent "going quiet," followed sometimes by many hours of working just fine. My mechanic advised that I was lucky to make it this long, as they tend to go bad after a few years. They are relatively inexpensive; I had kept one on the shelf for a long time, so we were ready to go!
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Re: Failed Aux Fuel Pump (Facet)?

Postby dstclair » Fri Dec 01, 2017 5:25 pm

I had a false positive :(

Aux Pump worked fine for a couple flights but yesterday spun up as usual and abruptly went silent. Flipped the switch off then on -- and nothing. Fuel pressure was reading zero. Decided to start up the engine anyway and the mechanical pump worked fine. Did a run up for no particular reason then powered off. Checked the aux pump -- and lo and behold it works.

I should've listened to Rich and replaced the pump a few weeks ago.
The first indications were intermittent "going quiet," followed sometimes by many hours of working just fine.

Now my mechanic is busy for two weeks so I'm grounded for a while. :cry:
dave

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Re: Failed Aux Fuel Pump (Facet)?

Postby dstclair » Tue Dec 12, 2017 10:31 am

Successfully replaced my failed aux pump. For those Sting owners, this is a two person operation. One person has to contort themselves to secure the nuts inside the cockpit while the other is loosing the bolt. It is also not easy to get to the aux pump on the engine side.

Now here's the interesting factoid. I had my mechanical fuel pump replaced with the 'new' pump 2-3 years ago. My engine has never skipped a beat but the pressure would occasionally drop to 1.8 - 2.2 from 3.5 - 4.0, then bounce back again. The Rotax SB mentions the new pump could do this so I assumed this was normal operation. Getting warning lights wasn't my favorite so the last year or so, I just kept the aux pump engaged all the time (like the RV-12 SLSA). This ensured that the lower range was always in the green.

I've had 3 flights with the new aux pump and I'm using it in typical fashion again (take off, landing and climbs as per a TL-Ultralight SB). Now when the aux pump is 'off', my fuel pressure is steady at ~4.0 PSI. I'm almost getting confident enough to fly like I did for 8+ years -- never engaging the aux pump in flight. Is it possible that my old pump, even when 'off', was causing fuel pressure issues?
dave

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Re: Failed Aux Fuel Pump (Facet)?

Postby drdehave » Tue Dec 12, 2017 11:17 am

Hah! That's two of us. Since replacing both my mechanical and electrical pumps a few months ago, my out-of-bounds pressure readings have 100% stopped! I deleted turning on the electrical from checklists :mrgreen:
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