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herman pahls
08-21-2011, 10:47 PM
I am considering removing the stock engine driven fuel pump on my Jabiru and going with gravity fuel flow and using a Facet fuel pump for take off and landing.
I believe the facet fuel pump is used as a back up pump on the Vans RV airplanes.
When the Facet pump is not powered will fuel flow freely and not be a restriction?
Thanks Herman

ackselle
08-22-2011, 05:41 AM
Herman,

According to the AS website, "fuel will flow through in the event of a pump failure".... I think that means "yes".

Cheers,
Ackselle

Jerrytex
08-22-2011, 07:26 AM
I have this same setup on my plane and the fuel flows through the pump with no issues when the pump is off. It is only used on Takeoff and landing or as a backup in case the engine driven pump quits. They are rather loud too.

avidflyer
08-22-2011, 09:29 PM
I also removed my mechanical fuel pump and now have an electric fuel pump on my Jabiru powered Avid MK IV. I still have the stock 2.5 MM seat for the float needle. I've been meaning to put the 3.7 MM seat in but have yet to order it from Bing Carbs. I use my electric fuel pump for full throttel operations, but have been told that if I put the 3.7 MM seat in, I will not need the fuel pump as the larger seat will flow enough fuel to run the engine at full throttel. The reason I got rid of the mechanical fuel pump is because it was putting out too much pressure and flooding the engine when I pulled the throttel back to idle when comming in to land. I don't use the electric fuel pump for landing. (Had to come back and add this) The pump does not act as a restriction in the line, fuel will flow freely through it when it isn't running. Take care, Jim Chuk

DesertFox4
08-23-2011, 12:33 PM
I have a back up Facet fuel pump between my header tank and engine fuel pump. I did a flow test before first engine start to confirm its "flow through" capability. It did not restrict gravity flow rates when turned off.

Please do a flow check on any electric pump you may add to your system before flight just in case there has been a design change or in case you got a defective pump and it does not allow free flow when in the off position.

herman pahls
08-23-2011, 10:27 PM
I appreciate the replys and the advice to check the pumps flow when not in use.
I was told the stock Jabiru fuel pump will freely flow fuel with gravity.
My pump does not, maybe because my Kitfox has a 8 gallon cowl tank and does not have as much gravity as wing tanks with and a header tank.
I will order a 3.7 needle and seat.
I am considering removing the stock pump and going with gravity with the Facet as a back-up for take off, steep climbs and landing.

Does this forum feel there would be enough gravity from a cowl tank that at the lowest fuel level would only be 8 inches above the carb inlet at level flight?
I am considering using a fuel pressure gauge to confirm that the facet pump is functioning.
Thanks Herman

avidflyer
08-24-2011, 09:33 PM
Don't know what to tell you on the gravity feed with the low tank, I guess you will just have to do flow tests to find out for sure. When I went to the faucet pump and got rid of the engine driven pump, the origanial pump was putting out to much pressure and flooding the engine when pulled back to idle. Found out that the Avid doesn't glide as far as I thought with the engine out. Landed on a frozen lake with no problems, but at least I can now say I've experienced a for real engine out at 1000'. Take care, Jim Chuk

herman pahls
08-25-2011, 01:12 AM
Jim
I experienced my first for real engine out (Jabiru 80 hp) last Friday after 34 years and 16 years in the Kitfox(Jabiru for 3 years).
Fortunately I was at 1500 feet AGL and found the perfect cow pasture.
I tried restarting once and it ran for a second, then I decided to concentrate getting it down.
I wish I had run out of gas so the mystery would be solved.
Unfortunately running out of fuel looks bad to the FAA and the news.
After trailering the Kitfox back to the airport it started right up and ran great. I did not fly it.
I put a pressure gage after the stock Jabiru mechanical fuel pump and it read 3 pounds. (Jim; my fuel pump also flooded the carb until Jabiru Pacific sent me a fuel pump rebuild kit that reduces the pressure).
The fuel filter and gasculator flowed 10 gals/hour with gavity with 1/4 inch lines.
I found that my mechanical Jabiru pump does no flow at all with gravity from a cowl tank. I need see if it will flow with more gravity.
My wing tank only transfers fuel to the cowl tank so no increase in gravity like normal wing tanks would have.
My cowl tank for years has been vented to the top of the wing tank which means that when the wing tank is full, fuel will go down the vent line.
Would this fuel cause a venting blockage??
Do most Kitfox's have there collector tank vented this way?
The wing tank has a filler cap with the 90 degree bent tube into the airstream.
Maybe the vent tube got pinched when folding the wings out for flight which I do every time I fly. I do not see how it could be pinched.
I have carb heat to the 40mm Bing carb but was not using it when engine quit.
There did not seem to be a reduction in RPM to indicate carb ice or would the constant velocity nature of the Bing mask ice restriction to a point.
Since the dead stick landing.
I have increased all the fuel lines to 3/8's.
I will install a 3.7 Bing needle and seat.
I have installed a facet 3-4 PSI pump after the gasculator.
I want to see if the facet pump will pump thru the stock Jabiru pump.
If not, I see the Jabiru pump as a liability.
If I had true wing tanks I would go with gravity only, not use the mechanical pump and maybe use the facet as a back-up.
I hesitate flying without a reason for the engine out.
Any ideas or suggestions.
Thanks Herman

avidflyer
08-25-2011, 10:02 PM
When I first had problems with my engine I had about 350 hrs on it. It ran fine at full throttel and cruise, but when I pulled the power to come in to land, it died. Don't know why it never gave problems earlier but it didn't. I had landed on a frozen lake, (I fly on skis in winter) and had shut down and when I went to start it about 10 minutes later, it fired up, then died and then wouldn't start. When I had almost run the battery dead, it finally fired up. I flew around the lake a few times and it seemed okey, so I headed for home. I was comming in to land and when I pulled the throttel back to idle, it died. At first I thought I was going to have to land in the neighbor's field cause I was just a bit low to clear the trees at the edge of my field. I worked the throttel in and out, and it caught again and I made it over the trees and landed on my strip. It died again when I cut the power. In searching for the cause, I talked to Bing carb and described some of the symtoms. If for instance, I would idle the engine, when I shut it down, fuel would run out of the throat of the carb. Anyway, the first thing the guy at Bing said was you have to much fuel pressure. I tried all kinds of other things, Was flying with a new carb when I had the engine out where I landed on the lake. In the end, I got rid of the original fuel pump and went with a 1 1/2 - 2 1/2 lb faucet fuel pump. No problems since, the only time I use the pump is for full throttel operation. I would be worrying about over pressure with a 2 - 4 lb pump, especially when pulled back to idle as it it very easy to overpower the float needle valve and seat and the fuel level will get to high in the float bowl and it will flood the engine. I could get fuel running out of the carb when it was showing 3 lbs of fuel pressure in the fuel line. I really should get around to putting in the 3.7 MM seat from Bing, then I should be able to get rid of the pump for good, or just keep if for standby. Speaking of the 3.7 MM seat, if you are pushing fuel at 4 lbs of pressure, you are much more likly to overpower the needle valve than with the stock 2.5 MM seat. I guess what I'm trying to say, is I wouldn't go with that bigger fuel pump, as I think that 2 1/2 lbs of pressure is almost more than enough to overpower the 2.5 MM seat. Hope I haven't confused the issue worse for you. Give the guy at Bing a call, he is very helpfull and willing to talk. Take care, Jim Chuk

avidflyer
08-26-2011, 08:15 AM
Herman, I can't seem to find your phone #, I know I had it when we talked months ago, if you want to give me a call, we can talk easier than type. 218-254-2404 Take care, Jim Chuk

herman pahls
08-28-2011, 09:47 PM
One week ago I had my first for real dead stick landing with my Jabiru powered Kitfox and all went well.
Problem is the engine started and ran great after trailering it home a few hours later.
I tried re starting once in the air with no results.
I should have tried starting it after the landing but had my hands full with the authorities.
The main tank was full, the fuel system flowed 12 gals/hour at the gasculator, the stock Jabiru mechanical fuel pump is putting out 3 PSI and the carb. was clean and the main jet was clear.
Constant velocity carbs. are not supposed to get carb. ice???
I have a carb heat system but pulling carb heat does not reduce RPM like on a Lycoming.
The Bing carb. is supposed to be an altitude compensating carb. , so would that feature compensate when appliing carb. heat and there would be no detectable RPM drop.
Could ice have blocked the carb. without warning? Lycomings do give a warning?
I am pleased to be flying again but concerned that I did not find the reason for the engine quitting.
Thanks Herman

FoxDB
08-29-2011, 08:55 PM
Herman,
I don't believe 8" of drop would be enough to push through the facet pump and the needle and seat. I have a 582 with the pulse pump but I also added a pitot tube to the cowl tank cap. My thought is the ram air pressure may provide sufficient pressure to the carbs. (8" of fuel drop is only .21 PSI) (Pitot at 70 MPH = .09 PSI) .21+.09 = Maybe enough.
Dave

More food for thought: I made the mistake of connecting the carb vents together and running them down and out the bottom. The engine would run fine on the ramp but when I took off it caused a pressure drop in the float bowls and it would quit if brought to a low power setting.

herman pahls
08-30-2011, 09:38 PM
I want to thank everyone who posted ideas regarding my recent dead stick landing in my Kitfox on a 70 degree day.
DBFox; you are correct, cowl tanks do not produce adequet gravity to the carb..
I am more than ever convinced that my Jabiru quit due to carb. ice.
When I first installed the Jabiru I was told by many that Bing constant velocity carbs. do not ice by design.
Maybe they will not if the carb. air is coming from inside a warm cowl.
I spoke with Dave Jalanti and he said he has experienced carb ice on his Jabiru's and always uses Carb heat when operating at reduced power.
I fabricated a carb. heat system but admit that I rarely use it because pulling the carb. heat on a Jabiru does not give a RPM drop like a Continental or Lycoming due to the altitude compensation feature of the Bing.
I had descended from 9000 feet to 1500 feet at partial throttle and did not apply carb. heat.
The engine quit without warning and would not restart.
It started an hour later with no issues.
Next, I need to test how much heat my carb heat produces.
Any suggestions how to do this?
Thanks Herman