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Post by FormerCirrus on Apr 28, 2021 22:10:56 GMT
The day's first engine start today (914 engine) was difficult. I did the usual procedure:
1. Throttle closed
2. Aux fuel pump on
2. Choke lever fully down
3. Start engine and gradually move the throttle to 2500 rpm
4. Gradually bring the choke lever up to the off position
About halfway during the choke lever pull up, the engine would stumble and quit
Tried this about three times ... same result.
Sitting in the plane, I called Mark Gregor, who to my luck answered. Mark told me to move the throttle to 3000 rpm after startup and leave the choke fully engaged for 2-3 minutes before pulling it up. Worked and I taxied. Mark further advised to do a full power runup, which I did. Everything worked fine after that. Thanks (again) Mark!
Question: Why would the engine stumble like that? (Sort of like a Lycoming hot start.) It hadn't done that before in my 15 hours of ownership. (Mine is a 2018 demo model with fewer than 100 hours.) Possible relevant background: One, I had flown the day before without engine start problems. Two, it was 60-degrees F and dry outside. Three: the plane had a 100LL top-off between yesterday's flight and today's. I use 100LL and Decalin.
What should I look for on next time? Am I doing anything wrong? How will I know whether this was a transitory glitch or a clue to a larger problem?
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Post by buzz on Apr 28, 2021 22:47:47 GMT
How quick are you pulling the choke off? It takes me several minutes of gradually pulling the choke off otherwise it stumbles.
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Post by Glenn on Apr 28, 2021 23:16:24 GMT
Maybe it's a 914 thing. My 912 has never stumbled or hesitated during or after starts, winter or summer.
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Post by FormerCirrus on Apr 28, 2021 23:56:17 GMT
How quick are you pulling the choke off? It takes me several minutes of gradually pulling the choke off otherwise it stumbles. I had been, prior to today and Mark's advice (which also sounds like your practice), bringing it up pretty quickly after establishing 2500 rpm. |
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Post by buzz on Apr 29, 2021 0:11:48 GMT
How quick are you pulling the choke off? It takes me several minutes of gradually pulling the choke off otherwise it stumbles. I had been, prior to today and Mark's advice (which also sounds like your practice), bringing it up pretty quickly after establishing 2500 rpm. I guess my thought was that my experience was normal. When its cold on first start I have to baby it a little by slowly bringing the choke off and sometimes adding a little throttle to maintain 2500. When its warm out.... not so much. |
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Post by buzz on Apr 29, 2021 0:33:59 GMT
Don't consider myself an expert by any measure. Based on my experience I don't think you are doing anything wrong or missing anything. I do however understand your concern since you hadn't noticed it before. I forget where you are located. What has been the typical overnight temp? I'm in the Seattle area and have an unheated hanger. We are just now starting to stay consistently above freezing overnight and I know that the choke will be less of an issue as we warm up. I think as long as it is running normal in all other configurations and all readings are ok and you are performing your checks prior to TO I would think its ok.
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Post by jetcat3 on Apr 29, 2021 15:08:49 GMT
It all sounds normal, just leave the choke engaged for at least 2 mins and up to 5 minutes on cold starts around 2,000-2,500 RPM and then disengage it and you won’t notice a thing. It’s definitely a 914 specific technique I’ve observed.
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Post by FormerCirrus on Apr 30, 2021 1:35:34 GMT
It all sounds normal, just leave the choke engaged for at least 2 mins and up to 5 minutes on cold starts around 2,000-2,500 RPM and then disengage it and you won’t notice a thing. It’s definitely a 914 specific technique I’ve observed. Thanks. Flew today, following yours and Buzz's advice. All good. |
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Post by FormerCirrus on May 11, 2021 22:51:27 GMT
UPDATE: No mechanical or electrical issues at all. I had simply drifted into bad startup technique. A local (to KWVI) Tecnam and Rotax expert, Gryphon MacArthur, took a look under my cowling, and saw nothing wrong with the choke or throttle levers. Before undertaking the laborious process of opening the carb bowl, Gryphon sat in the passenger seat and watched me start the plane. And that was the problem.
Gryphon recommends this: Full choke, idle throttle, start the plane. Wait until the engine smooths out. Leave the choke in, but add throttle in 100 rpm steps. In my plane, that results in a slight rough engine sound for 10-20 seconds, then it smooths out. Add another 100 rpm, wait for smooth, add another 100 rpm, wait for smooth ... until 2200. Maybe 2500 on colder days.
Then remove choke at all once.
Worked for me. No need for choke on subsequent starts.
Gryphon also recommends a shutdown technique. Throttle at idle, turn off ignition, but pause a half-second at R and L on the way to off. Results in a softer shutdown.
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Post by grantopperman on May 11, 2021 22:59:07 GMT
Glad you resolved it. It's interesting: All these planes seem to be slightly different. Mine starts up with practically no choke in all but the coldest weather, smooth from the start. I've heard lots of variation from different pilots. You just have to learn your own plane!
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Post by jetcat3 on May 12, 2021 14:36:14 GMT
UPDATE: No mechanical or electrical issues at all. I had simply drifted into bad startup technique. A local (to KWVI) Tecnam and Rotax expert, Gryphon MacArthur, took a look under my cowling, and saw nothing wrong with the choke or throttle levers. Before undertaking the laborious process of opening the carb bowl, Gryphon sat in the passenger seat and watched me start the plane. And that was the problem. Gryphon recommends this: Full choke, idle throttle, start the plane. Wait until the engine smooths out. Leave the choke in, but add throttle in 100 rpm steps. In my plane, that results in a slight rough engine sound for 10-20 seconds, then it smooths out. Add another 100 rpm, wait for smooth, add another 100 rpm, wait for smooth ... until 2200. Maybe 2500 on colder days. Then remove choke at all once. Worked for me. No need for choke on subsequent starts. Gryphon also recommends a shutdown technique. Throttle at idle, turn off ignition, but pause a half-second at R and L on the way to off. Results in a softer shutdown. Yep, all normal and exactly what my Dad and I experienced with our 914. I like to leave the choke on for a while with the first cold start as you can still taxi with it on and when you fully remove it after 2-5 minutes you won’t have that rough transition like you experienced. |
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