So this has happened to me twice now, and I don't know if it is standard Lycoming behavior, or if I should be troubleshooting my airplane.
I have a O-360-A1A with aftermarket Fuel Injection (Airflow Performance) and a purge valve. I've got dual P-MAG 114's with Auto Spark Plugs. The airplane starts cold like a dream with MAYBE 2 seconds of prime.
When the engine is hot, I'll use the purge valve to cycle cool fuel into the spider and the engine starts with no problems.
A couple times now though, I've underestimated how warm the engine is, and have attempted my cold start with 2 seconds of prime when the engine has flown within an hour and is warm. Twice now, the engine has fired, and the prop has rotated backwards (counter-clockwise from the cockpit). The first time was accompanied with a little smoke and burned Avgas smell, the second time (a few weeks later) was much less exciting.
Now, obviously this isn't good for the engine. My first thought was that something was wrong with the timing of the P-MAG's. I have mine indexed 2 degrees after TDC, and the P-MAG should retard another 4 during start, so 6 degrees after TDC should be well past the point of kicking the motor around the wrong way. I took the cowl off today and checked the timing, both green lights came on at the same time at 2 degrees past TDC.
My other thought is the excess fuel is simply being ignited by the wasted spark during the exhaust stroke? The answer here is less prime.
Any other ideas or things I should check? The engine runs smooth in flight, with CHT's in the 300's now (50 degrees outside) and 350's during the summer months. Oil temperature is right around 190 degrees, and EGT's have a fair spread, but typically peak around 1400-1450. When leaning. The engine runs smooth. Mag check drops ~150rpm at 1,600rpm during runup, but runs really smooth.
Is this normal behavior if one overprimes a fuel injected engine during a hot start? I just want to understand what's happening, and also avoid this in the future so I don't have to replace a ring gear or starter.
I have a O-360-A1A with aftermarket Fuel Injection (Airflow Performance) and a purge valve. I've got dual P-MAG 114's with Auto Spark Plugs. The airplane starts cold like a dream with MAYBE 2 seconds of prime.
When the engine is hot, I'll use the purge valve to cycle cool fuel into the spider and the engine starts with no problems.
A couple times now though, I've underestimated how warm the engine is, and have attempted my cold start with 2 seconds of prime when the engine has flown within an hour and is warm. Twice now, the engine has fired, and the prop has rotated backwards (counter-clockwise from the cockpit). The first time was accompanied with a little smoke and burned Avgas smell, the second time (a few weeks later) was much less exciting.
Now, obviously this isn't good for the engine. My first thought was that something was wrong with the timing of the P-MAG's. I have mine indexed 2 degrees after TDC, and the P-MAG should retard another 4 during start, so 6 degrees after TDC should be well past the point of kicking the motor around the wrong way. I took the cowl off today and checked the timing, both green lights came on at the same time at 2 degrees past TDC.
My other thought is the excess fuel is simply being ignited by the wasted spark during the exhaust stroke? The answer here is less prime.
Any other ideas or things I should check? The engine runs smooth in flight, with CHT's in the 300's now (50 degrees outside) and 350's during the summer months. Oil temperature is right around 190 degrees, and EGT's have a fair spread, but typically peak around 1400-1450. When leaning. The engine runs smooth. Mag check drops ~150rpm at 1,600rpm during runup, but runs really smooth.
Is this normal behavior if one overprimes a fuel injected engine during a hot start? I just want to understand what's happening, and also avoid this in the future so I don't have to replace a ring gear or starter.