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difficult warm starts

J

jake15

I never have problems with cold starts or hot starts on the IO-390 with Avstar FI, but warm starts like after a cold start and 15 min taxi to the fuel pumps, then try to re-start after pumping gas can often be a pain. Tried using various methods but nothing works consistently. Just wondering what others do that might work.....
 
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Same here with my IO-320 in the RV-9A. Too hot for a cold start and not hot enough for a hot start. My solution is to go for a 20 minute walk!
 
I've had this issue on my -7 as well (IO-360). For the fuel pump start:
  1. Mix ICO
  2. Throttle cracked a litte more than cold start
  3. Crank
  4. Advance mixture until it catches
  5. Adjust throttle/mixture as needed
This avoids a flooded start if you were inclined to re-prime the warmish engine. YMMV.
 
Well, for warm starts, I go the opposite direction: I intentionally flood KELLI GIRL's IO-360, and she starts every time.

1. Throttle and mixture full forward.
2. Run the fuel boost pump for 6 seconds.
3. Throttle stays full forward, but bring mixture back to full aft (cutoff)
4. With the PMags (or mags) turned on, start cranking.
5. After about 8 seconds, my engine starts to catch. It fits and spits at first, but as the fuel/air mixture improves, the RPM comes right up.
At that moment...
6. Swap the throttle back with the mixture forward.

Randy "Monk" Richmond taught me that process about 7 years ago, and it has worked flawlessly. Zero backfires.
 
My friend Mike recommended this hot start procedure after I had a tough time learning to start a warm engine. This hasn't failed me so far.

1. Advance the throttle to about 1/4 throttle.
2. Mixture idle (the fuel pressure should still be 30 - 32 psi)
3. Start the engine until it catches
4. Advance the throttle slowly to keep the engine running while firmly advance the mixture to rich
5. Slowly retard the throttle to idle.


My test pilot did things differently

1. Mixture rich
2. Fuel pump on then off, slightly flooding the engine
3. Set throttle to full
4. Start engine until it catches
5. Aggressively move the throttle back to keep it from over reving,
and aggressively move it forward to keep it from stalling
6. After three or four cycles like this with the engine running, the throttle can be moved to idle and keep it there.
(not for the faint of heart)
 
If the engine hasn't gotten hot enough to boil the fuel in the spider lines but is warm enough to not require the extra fuel needed for a cold engine , then just 1/4" throttle and hit the start button.
 
Dynamics

Fuel - Air - Spark are required, in the right ratio, at the right time, for combustion to occur.

I think DanH talked about the "sweep" method (Rich to Lean, or Lean to Rich) in order to find that sweet spot.

When the engine is cold, this is pretty easy -- use the Throttle, Mixture, Boost pump to prime the system with fuel, close the throttle and then hit the start button.

When hot, you may or may not have any fuel in the lines between the fuel servo, the distribution spider, and the injectors. I've begun using the residual fuel pressure to "prime" the fuel lines/injectors -- basically open the throttle to full, mixture to full rich, watch the pressure bleed off a bit, then throttle back to high idle, and hit the start button.

Personally, I've never liked the "you need three hands" approach that seems to be practiced by some CFI's (i.e. Throttle Wide Open, Mixture Rich, Boost Pump On, Start Button, wait for a blade to catch, throttle closed, mixture lean, yaddah yaddah -- [juggle chainsaws here])...
 
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