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ghinman(at)mts.net
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 Posted: Fri Aug 15, 2008 6:18 am Post subject: Fuel pump not self priming |
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I just did the fuel flow test on my RV-8.
When first starting the electric fuel pump,it did not draw fuel from
the tank.I had to blow into the vent line to force fuel through to the
pump.
This means the pump is not self priming.This is a concern because if
I run one tank dry,and switch to the other tank I want it to draw fuel.
Have others noticed this?
I have fuel injection and Van's Airflow performance boost pump
P/N3090050.
Instruction with the pump say--
"Ideally the boost pump should be installed so that under normal flight
conditions the pump inlet will be gravity fed from the fuel supply"
I installed it per Van,s drawings. This shows the pump on the floor
of the cabin,but the filter is mounted vertically above.So it would not
be gravity
fed.
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George H. Inman
ghinman(at)mts.net
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rv8a2001(at)yahoo.com
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| Posted: Fri Aug 15, 2008 8:10 am Post subject: Fuel pump not self priming |
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This may be a case where once it is primed it will not have a problem from here on out. Try draining the line to the pump, hook everything back up and then hit the pump switch again. I bet it will be ok...........if not...........call AFP?
We also use these pumps here at work (same MFG) and have noticed that some of the pumps take 20~30 seconds to build up their pressure.
Scott Bilinski
RV-8a
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khorton01(at)rogers.com
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| Posted: Fri Aug 15, 2008 9:17 am Post subject: Fuel pump not self priming |
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I had the same problem the first time I tried to test my AFP boost pump. Then, while doing fuel flow testing, I inadvertently sucked the tank dry. I poured more fuel in the tank, and the boost pump reprimed just fine.
I don't know what is inside these pumps. Is it possible that there are seals that dry out after awhile, and this prevents the pump from priming? Maybe the problem does not exist when the seals are damp. I will do several flight tests, overhead the airport, where I run a tank dry and then switch tanks. I will do the tests with increasing time delay before switching tanks.
Kevin Horton
On Fri, Aug 15, 2008 at 09:08:13AM -0700, scott bilinski wrote:
[quote]
This may be a case where once it is primed it will not have a problem from here on out. Try draining the line to the pump, hook everything back up and then hit the pump switch again.?I bet it will be ok...........if not...........call AFP?
We also use these pumps here at work (same MFG) and have noticed that some of the pumps take 20~30 seconds to build up their pressure.
Scott Bilinski
RV-8a
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Ed Anderson
Joined: 10 Jan 2006
Posts: 475
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| Posted: Fri Aug 15, 2008 10:15 am Post subject: Fuel pump not self priming |
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George,
I use High pressure fuel pumps for my electronic fuel injected engine. I
have them both mounted as low as I could on the lower firewall (below the
level of the bottom of the wing tank). I have found (as you did) that once
"primed" they draw fuel just fine from the tanks. Most of the EFI pump
cautions will tell you that if no fuel to lubricate the pumps can quickly
result in damage to the pump.
So to address those concerns, I installed a small ("Van's" ) low pressure
Facet pump between the wing tanks and the pumps. I turn it on before
switching tanks. Once primed my pumps have never had to have the facet pump
on for starting and sucking fuel. However, even the smallest air leaks in
the line anywhere between the pumps and the tanks could cause loss of prime.
I use the facet pump on start up (to keep possibly dry pumps from damage)and
as mentioned - whenever getting ready to switch tanks. Its worked from me
for 10+ years.
Ed
Ed Anderson
Rv-6A N494BW Rotary Powered
Matthews, NC
eanderson(at)carolina.rr.com
http://www.andersonee.com
http://members.cox.net/rogersda/rotary/configs.htm#N494BW
http://www.dmack.net/mazda/index.html
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_________________
Ed Anderson
Rv-6A N494BW Rotary Powered
Matthews, NC
eanderson@carolina.rr.com |
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