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Boost pump

T

Treekiwi

I'm New Here
Hi all,
New RV6A owner with a question. My plane has a double rocker boost pump switches installed, and I'm wondering under what circumstances one would use the secondary boost? My previous low wing planes only had a single auxiliary pump switch. However, this plane has an io360, whereas my previous planes were carburetor.
I was warned by the previous owner to not use the boost for hot starts, and only 3 seconds for cold starts. I'm unsure whether this referred to the primary or secondary switch.
Thanks
Stephen
 
I've flown with the IO-360 and have the IO-360 in my plane. I only know of the single switch in each of the planes. Maybe the previous builder installed the double switch but it acts just like a single throw switch.

Search for the forum for hot start. I think when the engine is warm, meaning it was recently shutdown, the fuel is still pressurized and using the boost pump will make it too rich to start. I am still trying to learn how to reliably start a warm engine.
 
Per design there is the engine driven pump and one electric boost pump that's just a single speed on/off.

If you've got a double switch or two boost pumps that not the norm.
 
Treekiwi said:
Hi all,
New RV6A owner with a question. My plane has a double rocker boost pump switches installed, and I'm wondering under what circumstances one would use the secondary boost? My previous low wing planes only had a single auxiliary pump switch. However, this plane has an io360, whereas my previous planes were carburetor.
I was warned by the previous owner to not use the boost for hot starts, and only 3 seconds for cold starts. I'm unsure whether this referred to the primary or secondary switch.
Thanks
Stephen
Click to expand...

Would be good to know more about your aircraft's ignition and FI system. Do you know if you have a mechanical fuel pump on the engine? Are you perhaps using a SDI or EFII ignition and FI system? Did the previous owner give you any documentation?

If you have two pumps, are they equivalent, or one in each wing?

If you have two fuel pumps, you might be electrically dependent, which means for safety reasons you need to spend some time understanding your aircraft systems before flying.

There's a lot going on here, and the guy you bought the aircraft from might not have been the builder, and might not actually know the systems, so check things out for yourself - or find a solid, experienced RV builder/maintainer to help you.

Sorry to sound shrill, but you really don't want to have an incident like John Denver, which had as a contributing factor his lack of understanding of the aircraft's systems.
 
First you should probably look around to see if you actually have 2 electric boost pumps. Experimental builders do all sorts of things that they think make their plane better. Two boost pumps is not a standard configuration though. The switch may just be wired to allow some redundancy by putting two switches in parallel or have two positions which are equivalent.
 
Fuel pumps

rv8ch said:
Would be good to know more about your aircraft's ignition and FI system. Do you know if you have a mechanical fuel pump on the engine? Are you perhaps using a SDI or EFII ignition and FI system? Did the previous owner give you any documentation?

If you have two pumps, are they equivalent, or one in each wing?

If you have two fuel pumps, you might be electrically dependent, which means for safety reasons you need to spend some time understanding your aircraft systems before flying.

There's a lot going on here, and the guy you bought the aircraft from might not have been the builder, and might not actually know the systems, so check things out for yourself - or find a solid, experienced RV builder/maintainer to help you.

Sorry to sound shrill, but you really don't want to have an incident like John Denver, which had as a contributing factor his lack of understanding of the aircraft's systems.
Click to expand...

The engine is equipped with an Airflow Performance FI system. It has the standard engine driven fuel pump, so the electric auxiliary pump is only for takeoff, landing, and supplying fuel pressure for starts. Ignition is standard magnetos. My confusion arises from the second switch, and it's application for starting and/or priming. Everything else operates the same as every aircraft I have flown or owned. So far, I have not even engaged the secondary switch, as it doesn't really appear necessary, but I'm still intrigued to as to its purpose, and if anyone on this forum has seen anything similar.
 
First I would check what fuel pressure the pump provides in each position. You should be getting around 32 psi for your IO-360. Cessna 185 an 210 series aircraft use a 2 position switch, labeled hi & low. These are not actually 2 speed pumps, but rather are controlled by changing the voltage to the pump.
 
This isn't nearly as challenging as trying to figure it out on your own, but how about asking the previous owner what that switch is for? Did he put anything about it in the POH?

A secondary boost pump seems kinda odd to me...I can only speculate what it does (if anything).
 
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