The aux fuel pump on injected high wing engines is used for starting the engine and potentially in case of ‘emergency’ (ie engine not working properly, you can try to use it, see if it improves anything)
Nice story, I think it is not so bad it would stop on idle during flare, because it is running bit rough on very idle, but still not SO bad, it is way better when leaned, but still not so big deal.
I never use aux fuel pump, only for priming engine before start (Reims Rocket). Maybe there is aux fuel pump only for situations, when main fuel pump fails, injection needs pressurized fuel and only gravity feed is not sufficient for engine run. So the aux fuel pump is backup for main pump. Even in POH is mentioned only for starting engine.
This is from POH
vic wrote:
On a high wing aircraft there is no need for an extra fuel pump I´d say.
Not even if the engine is fuel injected? (Which the Reims Rocket engine is.)
Maybe stating the very obvious, but in a Reims Rocket, the aux fuel pump should not be on (neither hi nor lo) during normal takeoffs and landings, nor should it likely be during this test….
Well, I am not a mechanic, but if your test is OK at 1000rpm and the engine is still too rich, maybe the test setup isn’t right 
And the SID is most probably younger than the engine manual, so maybe something was learned by the time it was issued.
It reminds me of a friend who had an engine stoppage during the flare in a Reims Rocket (IO-360H). They stopped on the runway and the engine restarted after many attempts. The club mechanic found no issues except the super dirty plugs, complained about pilots who can’t make thses engines work etc… (you get the usual french grumbling 
)
The engine was running so rich it had stopped !
Well now I found in tables there is specified RPM with specific pressure. Now only have to check pressures by any mechanic with gauges and figure out why is it rich.
Thanks William, this is also what my friend said.
Anyway table 3 says idle is 600RPM for IO-360D, it says 1000RPM for IO-240. I will keep reading again and again, until I find those 1000RPM everyone is talking about. :)
Jelen wrote:
Should I do it on Idle (cca 650rpm), or on 1000RPM?
1000rpm
The text above speaks about SPECIFIED idle. Is is really nowhere specified in that long doc?
In my experience, in the context of these aircraft engines, the word “idle” is often used incorrectly. People very often speak about “idling at 1000 RPM” or similar, which is obviously sort of a contradiction, as “full” idle is usually somwhere somewhere at 500 RPM (and very “spluttery” in the flat fours and flat sixes).
Not sure this is the case here. Again, they should specificy the idle somewhere if they mention it.
Well I understand that, and clearly have to check this with someone who has right tools, maybe I will buy it, I saw few older test sets, not digital, but accurate steam gauges, but I am talking about testing. This test can do anyone as a preflight, or so, but it is not clear to me how to do it. Should I do it on Idle (cca 650rpm), or on 1000RPM?
SID says:
“With engine operating at the specified IDLE RPM and unmetered fuel pressure, slowly move the mixture control from the FULL RICH position toward IDLE CUT-OFF to check fuel/air mixture. A rise of 25 to 50 RPM should be obtained. An RPM change greater than 50 indicates the mixture is too rich and a change that is less than 25 indicates the mixture is too lean.”
BUT, engine manual says it should be done at 1000RPM. If I do it both ways, there is very significant difference.
