Wierd IO360 start behavior

[chepburn]

Good Morning...

My IO360A1B has exhibited a strange start behavior this winter. I haven't been as active this year, so have only managed to get flying one or twice a month.
I preheat the engine...Oil temp is around 50 when it is started up.

Standard cold start for me is prime for 5-6 seconds, throttle cracked, mixture ICO. The engine starts after a blade or two, and is firing on all 4. I advance mixture to about 50-75% and let things settle out. However, after about 10 seconds power goes to zero, and I have to juggle the throttle -way- up and back again (and adjust mixture as well) to keep the engine turning over... This dance goes on for about 60? seconds then the engine settles down. Sometimes I lose it and have to restart. Its behaving like I haven't selected a tank yet. ... no fuel to burn..

This behavior doesn't make me comfortable needless to say. Engine runs fine after this initial start problem.

I sump the tanks before start (no water evident..although not as much of an issue with FI)

Any ideas? I'd most like to know if the engine is telling me something I should be taking care of -now!-

Chris

[Toobuilder]

Try starting with mixture in full rich.

Also, I prime WOT. You are not moving much fuel with the throttle "cracked".

[chepburn]

Originally Posted by Toobuilder

Try starting with mixture in full rich.

Also, I prime WOT. You are not moving much fuel with the throttle "cracked".

I prime WOT and full rich as well... forgot to add that. When I crank it's at ICO until it catches.

[Low Pass]

Originally Posted by chepburn

I prime WOT and full rich as well... forgot to add that. When I crank it's at ICO until it catches.

That's similar to my/common hot start procedure. As mentioned above, for cold start, try starting full rich, idle throttle.

Hot start - cracked throttle, idle cut off. Crank, ignition on, add mixture/fuel slowly until it catches.

But... each one behaves slightly different.

[lr172]

Originally Posted by chepburn

Good Morning...

My IO360A1B has exhibited a strange start behavior this winter. I haven't been as active this year, so have only managed to get flying one or twice a month.
I preheat the engine...Oil temp is around 50 when it is started up.

Standard cold start for me is prime for 5-6 seconds, throttle cracked, mixture ICO. The engine starts after a blade or two, and is firing on all 4. I advance mixture to about 50-75% and let things settle out. However, after about 10 seconds power goes to zero, and I have to juggle the throttle -way- up and back again (and adjust mixture as well) to keep the engine turning over... This dance goes on for about 60? seconds then the engine settles down. Sometimes I lose it and have to restart. Its behaving like I haven't selected a tank yet. ... no fuel to burn..

This behavior doesn't make me comfortable needless to say. Engine runs fine after this initial start problem.

I sump the tanks before start (no water evident..although not as much of an issue with FI)

Any ideas? I'd most like to know if the engine is telling me something I should be taking care of -now!-

Chris

certainly sounds like intermittent or limited fuel delivery during the initial low RPM period. The priming should clear the lines of air. I would suspect that your mech fuel pump is slightly under-performing at low RPM and struggling to deliver the necessary rich mixture for the cold engine (a cold engine @0C can need almost twice as much fuel as a cold engine @20C during the start sequence and after start warmup). Given that you are starting at ICO and working the mixture, I would try the sequence with the boost pump on and see if it improves.

Larry

[skylor]

Originally Posted by chepburn

Good Morning...

My IO360A1B has exhibited a strange start behavior this winter. I haven't been as active this year, so have only managed to get flying one or twice a month.
I preheat the engine...Oil temp is around 50 when it is started up.

Standard cold start for me is prime for 5-6 seconds, throttle cracked, mixture ICO. The engine starts after a blade or two, and is firing on all 4. I advance mixture to about 50-75% and let things settle out. However, after about 10 seconds power goes to zero, and I have to juggle the throttle -way- up and back again (and adjust mixture as well) to keep the engine turning over... This dance goes on for about 60? seconds then the engine settles down. Sometimes I lose it and have to restart. Its behaving like I haven't selected a tank yet. ... no fuel to burn..

This behavior doesn't make me comfortable needless to say. Engine runs fine after this initial start problem.

I sump the tanks before start (no water evident..although not as much of an issue with FI)

Any ideas? I'd most like to know if the engine is telling me something I should be taking care of -now!-

Chris

Your start procedure is the same as mine (IO-360-A1B6), and I have very good luck with it. However, you prime for a much longer time than I do. For me, 2-3 seconds is plenty. With that said, I've experienced similar behavior during HOT starts if I advance the mixture too quickly. In my case, if the engine starts to die right after after firing and advancing the throttle keeps it going, it's actually an indication that there is too much fuel (possibly pooled in the intake).

Skylor

[airguy]

I'll start this by saying that I've got an all-electric fuel system, not an engine driven pump...

My best cold starts are mixture close to full rich, throttle idle plus half a turn open (vernier), hit the fuel pump about a half second ahead of the starter, catches on the third or fourth blade every time.

I think you may be overpriming yours if you need to cold-start in ICO, that's a good hot start procedure following a heatsoak of the fuel divider dumping fuel into the manifold.

My hot start procedure is another thing entirely - every engine has a sweet spot that works great, and I haven't found mine yet.

[GalinHdz]

Originally Posted by chepburn

Standard cold start for me is prime for 5-6 seconds, throttle cracked, mixture ICO.

FWIW: That sounds more like the hot start procedure for a fuel injected engine not for when the temperature is fairly cold. Try the same procedure but with mixture full rich and see if this makes a difference.

[skylor]

Originally Posted by GalinHdz

FWIW: That sounds more like the hot start procedure for a fuel injected engine not for when the temperature is fairly cold. Try the same procedure but with mixture full rich and see if this makes a difference.

Many use the ICO cold start procedure for FI Lycomings including at least one well known flight school in SoCal. This has worked flawlessly for me in 530 hours on my -8, as well as during a handful of hours in other aircraft such as Decathlons and Super Decathlons.

Skylor
RV-8

[chepburn]

Thanks for all the suggestions....

Just to be clearer, the engine starts well using the procedure I have outlined (BTW Its always usually 5-10 deg F when I am flying in the winter, sometimes colder) I'll give the Full mixture a try to see how that works for me, but current procedure works fine.

The problem that puzzles me is the engine dying after running for multiple seconds (like 10-15) Its like I have not selected my tank and it's fuel exhausted.

One suspect for me is the Gascolator. Unfortunately, we are forced to add gascolators in Canada even on FI installations... it's in the wing root on the left side, and its barely lower than the tank drain. When I sump it after not flying for weeks not much fuel comes out of it. (and the fuel selector is on left tank when I check.

Went flying again today, and lots of fuel came out of the gascolator when I checked it today... and the engine started, and kept running smoothly right through . I'm beginning to suspect that the engine is getting a big gulp of air from the gascolator right after it starts if it has been sitting for a long time... thus the fuel starvation effect.