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w7ikt(at)fly-web.us
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 Posted: Sat Apr 21, 2012 4:46 am Post subject: N912RV power failure on takeoff |
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Has anyone else had a problem with an automotive 12v electric fuel pump?
The following is the story of trouble shooting the engine quit on takeoff.
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With permission from the NTSB and the help of my son I trouble shot the loss of power.
· Checked inside the right tank for debris none found.
· The tank appeared empty, no gas came out of quick drain. We removed the quick drain with a pan to catch any gas or debris. We drained about and ounce of gas trapped because the quick drain extends into the wing. No water and just a few specks of dirt were found.
· Removed mechanical fuel pump and it worked properly.
· The clear fuel filter (in fuel line going to mechanical pump) was empty.
· We tried blowing air into the tank from the fuel hose that connects to the input of the mechanical pump. Unable to blow air into either tank.
· The rout of fuel to the mechanical fuel pump is: Tank, fuel selector 12v Electric fuel pump, clear glass fuel filter, mechanical pump.
· We removed the hose between the fuel selector and 12v electric fuel pump. Still unable to blow through the electric pump. Note, all that is left is 1 hose and the 12v electric pump. All the fuel hoses were in good condition, no swelling, able to look thru the short hoses.
· We removed the wings because the spars prevented access to the 12v electric fuel pump. Access to the electric pump was still difficult thru a hole in the seat bottom. After we removed the electric pump it was no longer restricted. The removal process cleared the obstruction. We checked the fuel line from the mechanical fuel pump to the electric pump for debris, none found.
When telling the trouble shooting story on the airport a pilot friend said he had a similar problem with an automotive electric fuel pump in a SkyBolt he built years ago.
Note the Facet 574A fuel pump was supplied in the Aero Designs Kit. It is turned on for 15 seconds prior to engine start. There have been reports of the electric pump and mechanical pump both on flooding the carb’s. I did see higher than recommended pressures during flight testing with the electric pump on.
It took 4 minutes for the engine to reach 120F before starting takeoff. About half the time was taxi, the other half at 4000 rpm waiting for the oil temperature to reach 120F. Do not know how many ounces of fuel the carb's hold. Wonder if the 4 minutes + was just running on fuel in the carbs?
--
God Bless
Bob Heiser W7IKT
[quote][b]
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mortweaver(at)sbcglobal.n
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| Posted: Sat Apr 21, 2012 6:01 am Post subject: N912RV power failure on takeoff |
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Bob,
Last year, during trip to Lawrence to attend reunion, I experienced fuel starvation that caused rough engine operation (could barely maintain altitude). I diverted 10 miles off course and made it to the nearest airport as identified on my Garmin 496 GPS. Switching fuel tanks made no improvement in rough engine operation. Before landing, I was already regretting the installation of an in-line fuel filter with the fuel pump. Upon landing, I discovered that the in-line NAPA fuel filter (glass cylinder with removable filter element) was indeed the problem. No clearly visible debris trapped in fine brass filter screen. Much resistance though when I tried to blow through it with one end blocked. When held up to bright light, it was visible that it was approx. 90% blocked. The engine operated normally with the filter element left out. Gasoline will deposit a varnish like residue in fuel systems. With a good gascolator I am convinced that any other filter on the output side of the firewall mounted gascolator is more of a hazard and offers little benefit. I run 87 octane auto fuel with up to 10% ethanol and the 912 UL engine runs clean and reliable. The fuel sealer in all 3 tanks on the XP seems to be holding up well. Fuel tank coating debris is something I watch for in the gascolator collection bowl. I have no experience with any problems with the Facett electric fuel pump. I do monitor fuel pressure on my panel. As far as I know, the one way valves in the Facett pump are extremely reliable.
Dave Weaver N912GR
--- On Sat, 4/21/12, Bob Heiser <w7ikt(at)fly-web.us> wrote:
| Quote: |
From: Bob Heiser <w7ikt(at)fly-web.us>
Subject: N912RV power failure on takeoff
To: pulsar-list(at)matronics.com, rotaxengines-list(at)matronics.com
Date: Saturday, April 21, 2012, 7:44 AM
Has anyone else had a problem with an automotive 12v electric fuel pump?
The following is the story of trouble shooting the engine quit on takeoff.
==========================================
With permission from the NTSB and the help of my son I trouble shot the loss of power.
· Checked inside the right tank for debris none found.
· The tank appeared empty, no gas came out of quick drain. We removed the quick drain with a pan to catch any gas or debris. We drained about and ounce of gas trapped because the quick drain extends into the wing. No water and just a few specks of dirt were found.
· Removed mechanical fuel pump and it worked properly.
· The clear fuel filter (in fuel line going to mechanical pump) was empty.
· We tried blowing air into the tank from the fuel hose that connects to the input of the mechanical pump. Unable to blow air into either tank.
· The rout of fuel to the mechanical fuel pump is: Tank, fuel selector 12v Electric fuel pump, clear glass fuel filter, mechanical pump.
· We removed the hose between the fuel selector and 12v electric fuel pump. Still unable to blow through the electric pump. Note, all that is left is 1 hose and the 12v electric pump. All the fuel hoses were in good condition, no swelling, able to look thru the short hoses.
· We removed the wings because the spars prevented access to the 12v electric fuel pump. Access to the electric pump was still difficult thru a hole in the seat bottom. After we removed the electric pump it was no longer restricted. The removal process cleared the obstruction. We checked the fuel line from the mechanical fuel pump to the electric pump for debris, none found.
When telling the trouble shooting story on the airport a pilot friend said he had a similar problem with an automotive electric fuel pump in a SkyBolt he built years ago.
Note the Facet 574A fuel pump was supplied in the Aero Designs Kit. It is turned on for 15 seconds prior to engine start. There have been reports of the electric pump and mechanical pump both on flooding the carb’s. I did see higher than recommended pressures during flight testing with the electric pump on.
It took 4 minutes for the engine to reach 120F before starting takeoff. About half the time was taxi, the other half at 4000 rpm waiting for the oil temperature to reach 120F. Do not know how many ounces of fuel the carb's hold. Wonder if the 4 minutes + was just running on fuel in the carbs?
--
God Bless
Bob Heiser W7IKT
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Thom Riddle
Joined: 10 Jan 2006
Posts: 1597
Location: Buffalo, NY, USA (9G0)
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| Posted: Sun Apr 22, 2012 4:09 am Post subject: Re: N912RV power failure on takeoff |
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Bob,
"After we removed the electric pump it was no longer restricted. The removal process cleared the obstruction. "
I suspect the reason that removing the fuel pump removed the "obstruction" is that diaphragm pumps all have check-valves. They won't work without one-way check-valves. I'd bet that if you had tried blowing air through the system from the tank towards the engine (with tube disconnected at engine), you would have been able to.
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Thom Riddle
Buffalo, NY (9G0)
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BARRY CHECK 6
Joined: 15 Mar 2011
Posts: 738
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| Posted: Sun Apr 22, 2012 7:08 am Post subject: N912RV power failure on takeoff |
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Good point Thom:
| Quote: | I suspect the reason that removing the fuel pump removed the "obstruction" is that diaphragm pumps all have check-valves. They won't work without one-way check-valves. I'd bet that if you had tried blowing air through the system from the tank towards the engine (with tube disconnected at engine), you would have been able to.
--------
Thom Riddle
Buffalo, NY (9G0)
Kolb Slingshot SS-021
Jabiru 2200A #1574
Tennessee Prop 64x32
Truth is what stands the test of experience.
- Albert Einstein
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Experience is what you get from failures.
- Barry
The diagnosis process was faulty. You MUST start from a known. The known being there was no fuel flow. Then check as much of the system as possible with disturbing as little as possible. One thought that came to mind was Mud Daubers - I say that because there were no mentions of assembly procedures.
Barry
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