Fuel pressure, sensor

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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bstrachan
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Re: Fuel pressure, sensor

Postby bstrachan » Wed Nov 04, 2015 10:39 am

3Dreaming wrote:The fuel flow though the needle is less, 5GPH/2=2.5 per carb.


Just wanted to see if you were paying attention :wink:

Seems to me this would make it even more believable that the carbs (!) can get enough fuel flow with low pressure on the inlet. Two carbs = half the restriction

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bstrachan
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Re: Fuel pressure, sensor

Postby bstrachan » Sun Nov 08, 2015 9:37 am

Yesterday I did a 4 hour cross-country... fuel pressure was solid above 3 PSI all the time. In fact, I started using that new Shell "V-Power" premium about a month ago and I don't think I've had a low fuel pressure indication since. Coincidence? Probably, but whatever it is, I like it :D

BTW, Shell gas (here in Cedar City anyway) does not contain any ethanol. I bought one of those test kits and confirmed for myself that it will detect as little as 2% ethanol. Shell premium has always tested 0% for the last two or three years.

I don't work for the Shell Oil Co. 8)

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bstrachan
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Re: Fuel pressure, sensor

Postby bstrachan » Sun Nov 08, 2015 10:35 am

Another thought: when Shell announced this new "V-Power" I was skeptical. They don't say what's in it, unlike Chevron's Techron which has a description on the net ("Techron uses a polyether amine (PEA)-based chemistry that's unbeatable at cleaning and protecting your engine"). I've also read articles that say Techron is so good that people add it to other brands of gas. So I went to Chevron premium for a few months in the airplane, while continuing to use Shell in my cars. After awhile I didn't notice any bad effects with the new Shell premium in the cars, so I started using it in the aiplane again about a month ago. Maybe.... just maybe.... that Techron cleaned up some deposits in my fuel system and I am now reaping the benefits. If the low pressure indication comes back, I'm going back to Chevron gas and see what happens.

To be continued.

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bstrachan
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Re: Fuel pressure, sensor

Postby bstrachan » Sat Nov 14, 2015 7:47 pm

3+ hour cross country today. No low fuel pressure indications. Still using Shell "V-Power" premium. ??????

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designrs
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Re: Fuel pressure, sensor

Postby designrs » Sun Nov 15, 2015 1:33 am

Great. I will have to check on that Shell V-Power here and test it to see if it has ethanol.

As for me, I'm testing with a mechanical Guage to see if low fuel pressure is Dynon related or actual mechanical.

Thus far, I have not had low fuel pressure warnings.
I did see the fuel pressure symptomaticlly drop to about 2.4, at which point the mechanical Guage correlated to the Dynon. Still waiting for the low warning condition.... a because I just have to know what area to trouble shoot.

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designrs
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Re: Fuel pressure, sensor

Postby designrs » Thu Nov 19, 2015 4:49 am

UPDATE: Tested extensively with a mechanical fuel pressure guage in parallel with the Dynon. Mechanical Guage was consistently 1 psi over Dynon / Kavlico. (Guage deviation, or possibly more pressure is there.)

My intent was to isolate the issue as either mechanical (pumps / hoses / clamps) or electrical (Dynon, senders, wiring, grounds)

Unfortunately I did not see a low fuel pressure warning below 2.2 psi.

What I did see was:
1) direct correlation between Dynon reading and mechanical guage.
2) "symptomatic" lower pressure patterns 2.4 to 2.7 (hoped it would progress lower for testing)

Conclusion: most likely NOT Dynon related

Next: now doing slightly early rubber replacement with my annual.

Thanks to all those following this thread.

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FastEddieB
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Re: Fuel pressure, sensor

Postby FastEddieB » Thu Nov 19, 2015 6:42 am

designrs wrote:...(Guage deviation, or possibly more pressure is there.)


Physics and/or fluid dynamics are not my forté, but...

...in a closed system, is not the pressure the same throughout?
Fast Eddie B.
Sky Arrow 600 E-LSA • N467SA
FastEddieB@mac.com

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designrs
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Re: Fuel pressure, sensor

Postby designrs » Thu Nov 19, 2015 8:18 am

Well obviously guages vary. The introduction of a "T" connector may make a difference (even if not in theory). Also any pinching of the hose or something like that. There are a lot of variables.

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MrMorden
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Re: Fuel pressure, sensor

Postby MrMorden » Thu Nov 19, 2015 9:04 am

designrs wrote:There are a lot of variables.


https://www.youtube.com/watch?v=XKVmpJaMffM


:lol:
Andy Walker
Athens, GA
Sport Pilot ASEL, LSRI
2007 Flight Design CTSW E-LSA

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drseti
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Re: Fuel pressure, sensor

Postby drseti » Thu Nov 19, 2015 10:13 am

What in god's holy name are you blathering about, Andy?
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
fly@AvSport.org
http://AvSport.org
http://facebook.com/SportFlying

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bstrachan
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Re: Fuel pressure, sensor

Postby bstrachan » Thu Nov 19, 2015 10:22 am

Right on about pressure in a closed system. Google Pascal's Law.

1 PSI is not much pressure. It's getting down to the point where you need a manometer or some exotic, calibrated gauge to make a really accurate measurement.

There are other reasons to think the low fuel pressure indication is NOT instrument related (it happens on so many different platforms, with different fuel pressure measurement devices). This dual gauge experiment supports that theory.

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MrMorden
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Re: Fuel pressure, sensor

Postby MrMorden » Thu Nov 19, 2015 11:07 am

drseti wrote:What in god's holy name are you blathering about, Andy?


Sorry, I never miss an opportunity to inject "The Big Lebowski" into the conversation. ;)
Andy Walker
Athens, GA
Sport Pilot ASEL, LSRI
2007 Flight Design CTSW E-LSA

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drseti
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Re: Fuel pressure, sensor

Postby drseti » Thu Nov 19, 2015 11:23 am

New s#!7 has come to light, man.
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
fly@AvSport.org
http://AvSport.org
http://facebook.com/SportFlying

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bstrachan
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Re: Fuel pressure, sensor

Postby bstrachan » Sat Nov 21, 2015 10:52 pm

1.5 hour scenic flight today. 40 minutes or so up at 11,500. Fuel pressure steady, >3.5 PSI. Still using Shell Premium. FWIW.

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designrs
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Re: Fuel pressure, sensor

Postby designrs » Sun Nov 22, 2015 7:51 pm

UPDATE:

I have spent MONTHS and $$$$ diligently trouble shooting this!
Replacing parts, researching everything, contacting the US importer, communicating with other owners with similar problems, etc.

Here's where it's at:

1) Mechanical fuel pressure gauge testing correlated with the Dynon readings. The problem is not electronic, sender, or Dynon.

2) US Sport Aircraft has updated the fuel system in the new SportCruisers. The whole system is completely different. Fuel distribution, routing, fuel pressure system, etc.. The main feature is a CHECK VALVE related to the electric pump and main fuel feed line to the mechanical pump, and also the elimination of a redundant fuel line. An upgrade kit is available for previous years.

3) Research indicates that ADDITIONAL RESTRICTION OF THE FUEL RETURN LINE would raise fuel pressures. I have heard of EXPERIMENTAL RV-12's having success with this. (Different rules about modification apply of course.)

4) Many aircraft with low wing, the NEW PUMP, and FUEL RETURN LINE are experiencing low fuel pressure issues, especially when operating in hot climates. Specific models that I have heard of include: SportCruiser, RV-12, Sting, etc.

5) In my opinion, it is VERY LAME that at least one major manufacturer requires the electric pump to be on at all times. That should NOT be required or necessary!

6) This is an INTERMITTENT problem that SOME aircraft experience under SOME conditions, making it especially troublesome.

7) There are many older model aircraft operating with NO FUEL RETURN LINE at all, running very simple and reliable fuel systems... and I'm not hearing any complaints!

It is extremely FRUSTRATING that "improved" systems and "improved" parts subject owners to theses worrisome issues.

** Looking at all available information and options to resolve this issue and expect progress. **


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