Another Archer III starting question.

MachFly

MachFly

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MachFly
So far I've been starting the engine by priming for a few seconds first, and not using the electric fuel pump on the ground at all. Using that procedure it started without a problem. Now I've been doing some reading from the POH and that says to turn the electric fuel pump on before starting and never says to turn it off. Yet for some reason it does not say to prime it at all. The primer is electric, could it be possibly calling the primer a fuel pump?
 
The POH method will work great when the OAT is fairly warm, say above 50ºF. Note, they say if it doesn't start in 10 seconds use prime.


When it is cold you want to use the primer right off, and the colder it is the more primer you use. At 32ºF four shots will be good. Wait about 15 seconds to let it vaporized, then start.

In any case, start with the electric fuel pump on, unless you are flooded, which would be difficult if it was cold.
 
The fuel pump on a carbureted engine only fills the float bowl, it does nothing at all to put fuel into the engine, vacuum does that. If the primer pump is electric, hit it accordingly to temperature, the colder it is, the more prime you need. If it's really cold sometimes you need to keep tapping it after the engine catches to keep t running until it's got some running temp in the heads, doesn't take but a few seconds.
 
I'm slightly confused regarding the electric fuel pump. I need to turn it on before starting, and turn it off after starting, correct?

From a mechanical point of view, what is the electric fuel pump doing that's needed for engine start? So far I've flown the plane twice, both times it started with the electric fuel pump off without too much trouble, although the engine was running a bit rough in the beginning.

I am concerned that keeping the electric fuel pump on may flood the engine, is that possible? If so, how likely?
 
Any by the way, the primer is electric.
 
MachFly said:
I'm slightly confused regarding the electric fuel pump. I need to turn it on before starting, and turn it off after starting, correct?

From a mechanical point of view, what is the electric fuel pump doing that's needed for engine start? So far I've flown the plane twice, both times it started with the electric fuel pump off without too much trouble, although the engine was running a bit rough in the beginning.

I am concerned that keeping the electric fuel pump on may flood the engine, is that possible? If so, how likely?
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Personally with a carb equipped plane that has an electric pump, I give a couple seconds before starting to make sure the fuel system and bowl has fuel pressed into it, then I turn it off and start the plane. Then I proceed to taxi and do my run up with it off, that way if my mechanically driven pump is bad, I'll run out of fuel before I take off. When I take the runway, the fuel pump comes on in the flow that brings the mixture to rich for takeoff, then goes off again in the flow for first power reduction. If for some reason I am flying to a high altitude, I'll turn the pump on again at around 12,000'.

The electric fuel pump in conjunction with a carburetor has NO possibility of flooding the engine unless the float and/or needle and seat are compromised, and even then the engine will experience the same problem whether the boost pump is on or not.
 
Alright I think got it, can you just confirm that I understood it correctly?

  • A few seconds of prime (given its cold outside)
  • electric fuel pump on
  • wait a few seconds
  • engauge the starter
  • electric fuel pump off

Is that correct?
 
MachFly said:
Alright I think got it, can you just confirm that I understood it correctly?

  • A few seconds of prime (given its cold outside)
  • electric fuel pump on
  • wait a few seconds
  • engauge the starter
  • electric fuel pump off

Is that correct?
Click to expand...

Unless the engine has been running and is still warm, I'll always give a tap of primer anyway, but yeah, you'll do fine with that.
 
Alright sounds good. Appreciate the help!
 
MachFly said:
From a mechanical point of view, what is the electric fuel pump doing that's needed for engine start?
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For Archers: If this engine has a carburetor then the electric fuel pump is a redundant fuel pump. Its purpose is to provide fuel pressure should the mechanical fuel pump go TU. Typically the pilot will turn it on during pre-flight and watch the fuel pressure gauge to make sure it is generating pressure, and then it may be turned off prior to engine start. Or it can be left on until after engine start. Typically your checklist will call for Electric Fuel Pump OFF before or during taxi, as this will starve/stall the engine if the mechanical pump is not working. So now you have checked both pumps.

Fuel injected engines are more complicated.

-Skip
 
Skip Miller said:
For Archers: If this engine has a carburetor then the electric fuel pump is a redundant fuel pump. Its purpose is to provide fuel pressure should the mechanical fuel pump go TU. Typically the pilot will turn it on during pre-flight and watch the fuel pressure gauge to make sure it is generating pressure, and then it may be turned off prior to engine start. Or it can be left on until after engine start. Typically your checklist will call for Electric Fuel Pump OFF before or during taxi, as this will starve/stall the engine if the mechanical pump is not working. So now you have checked both pumps.

Fuel injected engines are more complicated.

-Skip
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Understood, thanks.

95% of my flight experience is with injected engines, and whatever little experience I have with carburetors was with pump-type primers. So I'm a bit new to this whole "carburated-electric" setup.
 
MachFly said:
Understood, thanks.

95% of my flight experience is with injected engines, and whatever little experience I have with carburetors was with pump-type primers. So I'm a bit new to this whole "carburated-electric" setup.
Click to expand...

Unlike an injected engine where the electric fuel pump can be used to prime the engine, with a carbureted engine that won't work, so what you will have is a second electric pump as the prime pump that replaces the plunger you are accustomed to.
 
Henning said:
Unlike an injected engine where the electric fuel pump can be used to prime the engine, with a carbureted engine that won't work, so what you will have is a second electric pump as the prime pump that replaces the plunger you are accustomed to.
Click to expand...

Right, yeah I kinda figured that bit out in your first explanation of the starting procedure. The system should be simple enough, just something new and takes a bit of time getting used to.
 
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