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Electric Fuel Boost Pump, Yes or No

Picked up my “new” RV8A today. It has the IO 360 w 200hp, CS and 3 blade MBT prop. I received transition training in an RV7A from an approved Vans pilot. He taught, and it makes good sense to have the electric fuel boost pump on for takeoff and landings.
The fellow that I picked the airplane up from today has said that the electric fuel boost pump would not keep the engine running if the engine driven pump failed, so why run it in the air...
Opinions?
 
One of the preflight test for Phase 1 is to confirm that the electric boost pump can pump enough fuel to keep the engine running while the plane is in a nose up attitude, in case the engine driven pump fails. EAA Test Card 0.
If your plane can't do that then maybe it has the wrong electric fuel boost pump. IO engines need the high pressure boost pump.
 
This is an overly broad generalization and not 100% applicable across the board but for injected motors the electric boost pump is usually there to prime for start and serve as a backup in the event the engine driven pump fails. Many injected engines run the electric boost pump for T/O and Ldg only and shut it off for cruise. Some don't run it at all, it is there solely as an emergency backup.
If the installation in your aircraft is incapable of providing sufficient flow/pressure for your engine I have to wonder if it is properly sized.
 
When I bought my RV-9A, I landed for fuel 2/3 of the 500 miles to fly it home and when I went to restart, I noted that the engine driven pump was no longer generating enough fuel pressure to keep the engine running while taxiing. The boost pump would. It had failed at that moment. If I had taken off, engine-driven fuel pump had failed, and if I'd had a boost pump that wouldn't keep the engine running...the plane might still be sitting in an Iowa cornfield. I'm thinking of installing a second boost pump.
 
The symptoms you describe are quite common on FI engines following a hot start. The fuel lines are hot, the gas is boiling. The engine pump doesn’t pump vapor well. Running the electric pump, plus a few minutes of cool gas, should clear up the problem.
 
The symptoms you describe are quite common on FI engines following a hot start. The fuel lines are hot, the gas is boiling. The engine pump doesn’t pump vapor well. Running the electric pump, plus a few minutes of cool gas, should clear up the problem.

Unfortunately, it didn't in this case. No matter what I did or how long I waited, that fuel pump would not do more than 5 psi. No issues with the one the mechanic replaced it with, however. Now...I keep that sucker going til 1000 ft, then watch it like a hawk after I shut it off on cruise climb.
 
Many injected engines run the electric boost pump for T/O and Ldg only and shut it off for cruise. Some don't run it at all, it is there solely as an emergency backup.

Generally, with Lycoming engines (injected and carbureted) it is recommended to operate the boost pump for takeoff and landing, or in an emergency. The boost pump should not change the fuel flow to the engine. For injected continental engines, it is recommended to use the boost pump only in an emergency, or in some cases during high altitude, high ambient temperature operations when fuel vapor might be reducing fuel flow. On continental injected engines, the fuel boost pump actually increases fuel flow, particularly at low manifold pressure and can cause flooding of the engine at these low manifold pressure/power settings.

Skylor
 
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As I understand it, low wing aircraft cannot depend on gravity to feed fuel to the engine, so the auxiliary fuel pump is on for takeoff and landing. Whenever I turn the auxiliary pump off, I keep my finger on the switch in case the engine stumbles. When I first flew in an RV-8 with Bruce Bohannon, he related a story about taking off in a Mooney and having the engine driven pump fail about the time he switched off the auxiliary pump. After a few confusing moments, he switched the auxiliary pump on again and saved the flight.

My -8 has an O-360 and I’ve noticed that in cruise, fuel flow can drop below 2 psi without any change in the other engine parameters. I’m not sure if this is accurate or an issue with the red cube fuel pressure transducer.
 
Pump

Check your PMs

My son and I bought a beautiful RV-8 about this time last year. During the extensive pre-purchase, I noted that it had a Holley Blue pump and non-standard fuel lines/routing. I discovered that while this pump, in the standard configuration, is incapable of generating the minimum pressure needed, a different spring was/is offered (Moroso) to raise it to just meet the minimum requirement of our IO-360s. It was noted in the checklist that the pump was to be "OFF" unless the main pump failed. I discovered that this was not a one-off install in the earlier (pre-2005) birds which I understand is the result of a magazine article which described this lower cost alternative. The pump is NOT rated for continuous use and, in fact, will shut itself down if overheated. It does not recirculate fuel for cooling. I suspect this is exactly why the checklist calls for it to be OFF unless the mechanical pump fails. Additionally, because of the fuel line routing, no fuel pressure indication was available to indicate that it was working. The airplane had flown over 300 hours. I flew it home and immediately tore out everything from the fuel valve forward. Taped enlarged copies of the current Van's fuel system plan (thanks Office Max For the enlargements) to the hangar wall and replaced everything with all with new T&S teflon lined fuel lines and an AFP boost pump according to the current plans. The AFP pump supplies more than enough pressure, the system is now indicating a pressure increase when turned ON , is rated for continuous use, and the boost pump is now turned ON for every takeoff and landing. MUCH safer system.
 
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Picked up my “new” RV8A today. It has the IO 360 w 200hp, CS and 3 blade MBT prop. I received transition training in an RV7A from an approved Vans pilot. He taught, and it makes good sense to have the electric fuel boost pump on for takeoff and landings.
The fellow that I picked the airplane up from today has said that the electric fuel boost pump would not keep the engine running if the engine driven pump failed, so why run it in the air...
Opinions?

It should keep the engine running if the mechanical pump fails. This is a safety of flight issue.

Unfortunately, there's no easy way to physically verify that it does, so your homework is to determine which electric pump you have and verify that it is the correct pump for your application.
 
I found the EMS on my EFIS to be illuminating in terms of fuel pump adequacy. The engine-driven fuel pump failure resulted in a fuel-pressure annunciation from the AG6, and the EMS showed fuel pressure to be solidly in the red at 4-5 psi. Flipping on the boost pump bumped the pressure to 22 psi. In order to try to get home, the mechanic changed the busted pump out for one he had just taken off from a non-fuel injected engine he had sitting on the bench, but that only generated 7 psi. He installed the correct fuel-injected engine-driven pump a couple of days later and the AG6 and EMS have lived happily ever after.
 
fuel flow test

It should keep the engine running if the mechanical pump fails. This is a safety of flight issue.

Unfortunately, there's no easy way to physically verify that it does, so your homework is to determine which electric pump you have and verify that it is the correct pump for your application.
You can put the aircraft on an incline with the nose as high as you can get it, remove the fuel line just before the servo, and check the flow. I'm sure that the EAA has a documented procedure for this or there is probably a kitplanes or Bingelis article on how to do it. I found one and added the link below.

Definitely important. My Andair flowed over 50 GPH when I ran this test.

http://www.eaa1000.av.org/pix/erbpix/reports/fuelflow.pdf
 
I actually recommend leaving the electric boost pump on until top of climb, whether it's 1000' or 15K'. The fuel pump in our tightly-cowled RV's sits down low where all of the heat is exiting the cowling, and it is "sucking" the fuel uphill. Helping that diaphragm pump out with the electric boost pump will help stifle any potential vapor lock from "sucking." Sucking the fuel does lower the pressure, and especially if there are any small leaks from the pump to the tanks, that lowers the vapor pressure.

I do encourage the use of pump cooling shrouds, and use them on all of my airplanes.

Vic
 
I actually recommend leaving the electric boost pump on until top of climb, whether it's 1000' or 15K'. The fuel pump in our tightly-cowled RV's sits down low where all of the heat is exiting the cowling, and it is "sucking" the fuel uphill. Helping that diaphragm pump out with the electric boost pump will help stifle any potential vapor lock from "sucking." Sucking the fuel does lower the pressure, and especially if there are any small leaks from the pump to the tanks, that lowers the vapor pressure.

I do encourage the use of pump cooling shrouds, and use them on all of my airplanes.

Vic

Agreed.

I was having an issue on a trip across the country with my high pressure engine driven pump. Spoke with Don at AirflowPerformance about it. He said the electric pump can be run continuously, and will keep the engine running indefinitely. YMMV.
 
You can put the aircraft on an incline with the nose as high as you can get it, remove the fuel line just before the servo, and check the flow. I'm sure that the EAA has a documented procedure for this or there is probably a kitplanes or Bingelis article on how to do it. I found one and added the link below.

Definitely important. My Andair flowed over 50 GPH when I ran this test.

http://www.eaa1000.av.org/pix/erbpix/reports/fuelflow.pdf

Instead of putting the airplane on an incline, could you attach a hose to the end of the fuel line and raise that so the outlet is high enough to equal the incline method?
 
hydraulic head

Instead of putting the airplane on an incline, could you attach a hose to the end of the fuel line and raise that so the outlet is high enough to equal the incline method?
That would simulate the hydraulic head that the fuel pump needs to push against, which would be helpful, but it would not ensure that the fuel pickup in the tank is properly installed or does not have different behavior at the steeper angle of climb out.

Getting the aircraft to a exaggerated climb angle is easier with a taildragger, as you just need to find a little hill for the mains or a ditch to put the tailwheel in.

When I first thought about doing this I thought I'd just roll the aircraft up some standard car wheel ramps. That's easier said than done without a lot of help or some winches, and is pretty scary. A low place to put the tailwheel is much easier.
 
My -8 has an O-360 and I’ve noticed that in cruise, fuel flow can drop below 2 psi without any change in the other engine parameters. I’m not sure if this is accurate or an issue with the red cube fuel pressure transducer.

That is common in carb'd engines. My -8 with the same engine does it from time to time with no engine issues. Do a search as there are several threads on the subject.
 
There are some lycomings running the continental style injection system. ECI offered this type of injection for the IO360. Boost pump needs to be off with this system or you will flood the engine.
 
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