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stan2tew(at)gmail.com
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 Posted: Mon Jul 13, 2015 2:47 pm Post subject: 912 ULS Fuel Pressure |
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My 912 ULS mounted in my Rans S7-S has 438 hr. I replaced the old style mechanical pump as recommended by Rotax. I have an electric fuel pump and fuel pressure gauge. I usually take off with the electric pump running in addition to the mechanical pump. When I level off to cruise I turn off the electric pump. My pressure usually is about 4.5 psi. Last week I was flying and noticed the EIS warning light and it identified my fuel pressure to be about 0.9 psi. I quickly turned on the electric pump. The pressure went to about 3.5 psi. I flew back and landed without incident. The engine never faltered.
Any suggestion on how to test the mechanical pump? Any suggestion on what the problem might be? I have not had opportunity to remove the cowl to make any visual checks.
Stan Tew
N29TD
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Roger Lee
Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.
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| Posted: Tue Jul 14, 2015 4:56 pm Post subject: Re: 912 ULS Fuel Pressure |
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You can put a 10 psi gauge inline with the fuel at the balance tube assembly or if you don't have one then just plumb it inline. If your electric pump is plumbed in series it has a check valve that could cause an issue until it gets turned on.
I doubt it's the mechanical pump, but you won't know for sure until you put a gauge inline. Possibly the fuel pressure gauge, again an unknow until you put a gauge inline.
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Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
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John Hauck
Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)
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| Posted: Tue Jul 14, 2015 8:07 pm Post subject: 912 ULS Fuel Pressure |
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"T" a mechanical pressure gauge into your fuel line.
john h
Fort Lewis, WA
From: owner-rotaxengines-list-server(at)matronics.com [mailto:owner-rotaxengines-list-server(at)matronics.com] On Behalf Of Stan Tew
Sent: Monday, July 13, 2015 3:47 PM
To: rotaxengines-list(at)matronics.com
Subject: 912 ULS Fuel Pressure
My 912 ULS mounted in my Rans S7-S has 438 hr. I replaced the old style mechanical pump as recommended by Rotax. I have an electric fuel pump and fuel pressure gauge. I usually take off with the electric pump running in addition to the mechanical pump. When I level off to cruise I turn off the electric pump. My pressure usually is about 4.5 psi. Last week I was flying and noticed the EIS warning light and it identified my fuel pressure to be about 0.9 psi. I quickly turned on the electric pump. The pressure went to about 3.5 psi. I flew back and landed without incident. The engine never faltered.
Any suggestion on how to test the mechanical pump? Any suggestion on what the problem might be? I have not had opportunity to remove the cowl to make any visual checks.
Stan Tew
N29TD
01234567890123
[quote][b]
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John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama |
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rickofudall
Joined: 19 Sep 2009
Posts: 1392
Location: Udall, KS, USA
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| Posted: Sun Jul 19, 2015 5:47 am Post subject: 912 ULS Fuel Pressure |
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Stan, Check for blockage of tank vents. 'Tis the season for mud daubers after all.
Rick Girard
do not archive
On Tue, Jul 14, 2015 at 11:06 PM, John Hauck <jhauck(at)elmore.rr.com (jhauck(at)elmore.rr.com)> wrote:
| Quote: |
"T" a mechanical pressure gauge into your fuel line.
john h
Fort Lewis, WA
From: owner-rotaxengines-list-server(at)matronics.com (owner-rotaxengines-list-server(at)matronics.com) [mailto:owner-rotaxengines-list-server(at)matronics.com (owner-rotaxengines-list-server(at)matronics.com)] On Behalf Of Stan Tew
Sent: Monday, July 13, 2015 3:47 PM
To: rotaxengines-list(at)matronics.com (rotaxengines-list(at)matronics.com)
Subject: 912 ULS Fuel Pressure
My 912 ULS mounted in my Rans S7-S has 438 hr. I replaced the old style mechanical pump as recommended by Rotax. I have an electric fuel pump and fuel pressure gauge. I usually take off with the electric pump running in addition to the mechanical pump. When I level off to cruise I turn off the electric pump. My pressure usually is about 4.5 psi. Last week I was flying and noticed the EIS warning light and it identified my fuel pressure to be about 0.9 psi. I quickly turned on the electric pump. The pressure went to about 3.5 psi. I flew back and landed without incident. The engine never faltered.
Any suggestion on how to test the mechanical pump? Any suggestion on what the problem might be? I have not had opportunity to remove the cowl to make any visual checks.
Stan Tew
N29TD
01234567890123
4
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Believe those who are seeking the truth, doubt those who find it.
-Andre Gide
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b.carl@sympatico.ca
Joined: 20 May 2008
Posts: 77
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| Posted: Tue Jul 21, 2015 1:29 pm Post subject: 912 ULS Fuel Pressure |
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HI Stan
One year ago I had the same symptoms that you had. I believe this was caused by the fact that the electric pump has a slightly higher pressure than the engine pump and this causes the engine pump to stop pumping while the electric pump is "on." This stagnation of fuel in the engine pump during TO/Climb cause that fuel to vaporize and a momentary loss of pressure when the electric pump is turned "OFF".
I've moved my gascolator, filter and boost pump to the rear compartment and firesleeved all the lines. I also ran a return line to my right wing tank. Seam to have helped some but I still see the pressure drop and the occasional warning light when I turn the boost pump "OFF". Never affected the engine but always ready to reselect to boost pump.
After shutdown on a hot day burning auto fuel, put an ear close to the engine pump; bet you will hear the fuel boiling.
Carl
[quote] ---
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dpark748(at)icloud.com
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| Posted: Wed Jul 22, 2015 3:52 am Post subject: 912 ULS Fuel Pressure |
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I have exactly the same experience, this was after fitting the new mechanical pump which operates at a slightly higher pressure, it didn't happen before the new pump was fitted.?The drop in pressure does not effect the engine performance but am wary of switching the electric pump back on if required.
Regards Dave Park G-LDVO
On 21 Jul 2015, at 22:29, Carl <b.carl(at)sympatico.ca (b.carl(at)sympatico.ca)> wrote:
[quote]HI Stan
One year ago I had the same symptoms that you had. I believe this was caused by the fact that the electric pump has a slightly higher pressure than the engine pump and this causes the engine pump to stop pumping while the electric pump is "on." This stagnation of fuel in the engine pump during TO/Climb cause that fuel to vaporize and a momentary loss of pressure when the electric pump is turned "OFF".
I've moved my gascolator, filter and boost pump to the rear compartment and firesleeved all the lines. I also ran a return line to my right wing tank. Seam to have helped some but I still see the pressure drop and the occasional warning light when I turn the boost pump "OFF". Never affected the engine but always ready to reselect to boost pump.
After shutdown on a hot day burning auto fuel, put an ear close to the engine pump; bet you will hear the fuel boiling.
Carl
[quote]---
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rickofudall
Joined: 19 Sep 2009
Posts: 1392
Location: Udall, KS, USA
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| Posted: Wed Jul 22, 2015 6:54 pm Post subject: 912 ULS Fuel Pressure |
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When I was growing up vapor lock was not an uncommon in the autos of the 50's and 60's. Now it's virtually unheard of. Why? The engines of the time had block mounted fuel pumps. Fuel was pulled from the tank into a hot engine compartment. Sound familiar? Now the fuel pumps are in the tank and push fuel all the way to the injector rails. To keep the fuel, which is at 40+ psi, excess fuel is sent back to the tank to cool. Rotax has had the return line in its recommended fuel system but have the manufacturer's kept up with the rest of the system? A 912 ULS consumes 7 gallons an hour at full throttle. That's 1617 cu. in. of gas (air) that has to be let in to the tank to replace the 1617 cu. in. of gas that's been pumped out.
Do the simple things first and start with the basics. Check all vents to make sure they are clear. Next, raise the tail of the aircraft to flight position, disconnect the fuel line at the mechanical pump and time the fuel flow for 6 minutes. Measure how much fuel ran out and multiply X 10. That's the maximum fuel flow potential you can get to the pump. Until you know that you're just casting about in the dark.
Rick Girard
do not archive
On Wed, Jul 22, 2015 at 6:51 AM, david park <dpark748(at)icloud.com (dpark748(at)icloud.com)> wrote:
[quote]I have exactly the same experience, this was after fitting the new mechanical pump which operates at a slightly higher pressure, it didn't happen before the new pump was fitted.?The drop in pressure does not effect the engine performance but am wary of switching the electric pump back on if required.
Regards Dave Park G-LDVO
On 21 Jul 2015, at 22:29, Carl <b.carl(at)sympatico.ca (b.carl(at)sympatico.ca)> wrote:
[quote]HI Stan
One year ago I had the same symptoms that you had. I believe this was caused by the fact that the electric pump has a slightly higher pressure than the engine pump and this causes the engine pump to stop pumping while the electric pump is "on." This stagnation of fuel in the engine pump during TO/Climb cause that fuel to vaporize and a momentary loss of pressure when the electric pump is turned "OFF".
I've moved my gascolator, filter and boost pump to the rear compartment and firesleeved all the lines. I also ran a return line to my right wing tank. Seam to have helped some but I still see the pressure drop and the occasional warning light when I turn the boost pump "OFF". Never affected the engine but always ready to reselect to boost pump.
After shutdown on a hot day burning auto fuel, put an ear close to the engine pump; bet you will hear the fuel boiling.
Carl
[quote]---
| | - The Matronics RotaxEngines-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RotaxEngines-List |
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_________________
The smallest miracle right in front of you is enough to make you happy.... |
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