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  #71  
Old 06-26-2017, 09:19 AM
DHeal DHeal is offline
 
Join Date: Sep 2006
Location: Windsor, California
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Expanding upon what Joe said:

1) Turn on the Master Switch, listen for the electric fuel pump clicking and slowing down as system Fuel Pressure (FP) builds up, and look for @ 3 psi on the FP gauge. If the airplane is heat-soaked, let the electric fuel pump run for awhile (a minute or two) to allow cooler fuel from the fuel tank circulate through the fuel lines.

2) Start the engine and verify that the FP gauge is now showing @ 5 psi (i.e., reflecting the additional pressure of the now working engine-driven fuel pump).

3) During run-up, verify that FP remains @ 5 psi. If you want to double-check the fuel pump system, momentarily pull out the FP circuit breaker and verify that the FP is @ 3 psi with the engine-driven pump alone. Typically, I do not see any reason to do this if the FP is @ 5 psi.

4) In-flight, visually monitor the FP gauge as you would other engine instruments. The SV/Garmin units provide an additional visual/aural warning if FP drops.

5) After landing, shut-down the engine and listen for the clicking of the electric fuel pump before you turn off the Master.

The "full-time" electric fuel pump as installed in a standard RV-12 keeps cool fuel circulating, helps to avoid vapor lock, is not likely to be forgotten, and apparently has a relatively long service life. Others may prefer a switch-controllable electric fuel pump ala many low-wing airplanes -- I prefer the Van's factory set-up. As a critical flight item, I carry a spare electric pump with pre-attached electrical connectors and AN fittings -- just in case.
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David Heal - Windsor, CA (near Santa Rosa)
EAA #23982 - EAA Technical Counselor and Flight Advisor; CFI - A&I
RV-12 E-LSA #120496 (SV w/ AP and ADS-B) - N124DH flying since March 2014 - 520+ hours (as of July 2017)!
VAF donation through June 2018.
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  #72  
Old 06-26-2017, 10:40 AM
RFSchaller RFSchaller is offline
 
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Location: Phoenix, AZ
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Jim,

Your assumption that one pump failure will bring in the fuel pressure alarm is incorrect. I have been operating with a switched fuel pump for 5 years and see only a couple of tenths of a psi difference when I switch the electric pump on and off. As I said I just believe the scenario of losing the electric pump when the mechanical has failed is much worse than having to flip a switch in cruise if I experience vapor lock. Coupled with the operating experience of one vapor lock in 5 years (with old fuel) the approach I use seems sound.

A wise horse will check what's in the water and then decide whether to drink it.

Rich
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  #73  
Old 06-26-2017, 11:35 AM
DHeal DHeal is offline
 
Join Date: Sep 2006
Location: Windsor, California
Posts: 569
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Jim/Rich --

I agree that the loss of one of the two fuel pumps in-flight will likely not cause a "Yellow or Red" FP warning indication on the SV/Garmin and that the resultant loss in FP may be slight (in my RV-12, I do see a noticeable slight reduction in FP psi when I disable the electric pump in-flight) -- good points. I guess it all comes down to whether or not the pilot concurs with the benefits of Van's "full-time" electric pump use design philosophy versus a "use-it-when-you-want-it" philosophy. It is a question of whether or not one thinks the "full-time" electric pump will live a long and happy service life versus occasional switch-activated use. Suum Cuique

-- David

ps -- I will admit that I wonder how many cycles the FP fuse receptacle will tolerate over time since I remove/reinsert the FP fuse at least once every 28 days for data updates.
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David Heal - Windsor, CA (near Santa Rosa)
EAA #23982 - EAA Technical Counselor and Flight Advisor; CFI - A&I
RV-12 E-LSA #120496 (SV w/ AP and ADS-B) - N124DH flying since March 2014 - 520+ hours (as of July 2017)!
VAF donation through June 2018.

Last edited by DHeal : 06-26-2017 at 11:37 AM.
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  #74  
Old 06-26-2017, 06:24 PM
Piper J3's Avatar
Piper J3 Piper J3 is online now
 
Join Date: Nov 2014
Location: Hinckley, Ohio
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What about scenario where you re-start a hot engine, perhaps in a hot climate, and do not switch electric fuel pump on until ready for flight... Suppose fuel has boiled in supply lines and maybe even carb float bowls because under-cowl temps are very high and fuel system is heat-soaked.

What if you take off and engine stumbles at this very critical phase of flight?
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Jim Stricker
Hinckley, Ohio
PPL - 1970
80 hrs Flying Aeronca Chief 11AC
1130 hrs Flying 46 Piper J-3 Cub
RV-12 E-LSA #120058 AWC 7/12 Bought Flying 10/2015 with 48TT - Hobbs now 263
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  #75  
Old 06-26-2017, 08:14 PM
RFSchaller RFSchaller is offline
 
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Jim,

I'm not saying that one should never use the electric fuel pump if it's on a switch. I certainly agree that if the pilot thinks vapor lock is a strong possibility it should be on. I am glad to have experienced it and seen the immediate benefit the electric pump provided when I turned it on. I now know what a vapor lock scenario looks like which is also useful.

Rich
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