Vapor Lock Cessna 172

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Sarah__10

Filing Flight Plan
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Feb 26, 2017
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Sarah
Has anyone ever had experience with vapor locking an engine while coming into land with a low power setting?
 
Not sure if it was vapor lock, but I've had a 172SP (Lyc IO-360) that after landing wouldn't idle on a toasty high DA day at a 6000MSL airport no matter how I leaned the mixture. Seemed to run fine at higher power settings, though. Flew back to a lower altitude and it never did that again.
 
asicer said:
Not sure if it was vapor lock, but I've had a 172SP (Lyc IO-360) that after landing wouldn't idle on a toasty high DA day at a 6000MSL airport no matter how I leaned the mixture. Seemed to run fine at higher power settings, though. Flew back to a lower altitude and it never did that again.
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well I had been having issues with this aircraft studdering in flight..i had the fuel servo replaced and the next flight it ran great...I was on downwind and went to pull power and almost lost the engine...anytime I tried to pull power for the rest of the pattern, it tried to shut off. over the numbers, I pulled power and let the engine go and was able to get it back my playing with the throttle...about 15 mins after landing, it ran great and idled like a kitten...ran it about 1.5 hours today and couldn't duplicate the problem, so im kinda confused.. airport elevation is 1000' and the day it acted up on me the OAT was about 80..
 
I think vapor lock is fairly unusual in an injected engine, but there is a first time for everything (and you are never too old to learn).
 
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somorris said:
I think vapor lock is fairly unusual in an injected engine, but there is a first time for everything (and you are never too old to learn).
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Vapor lock doesn't only affect carb'd engines, it can affect FI systems as well. Often times, the reason a fuel injected engine has trouble starting, has a lot to do with vapor in the system, which prevents fuel from getting into the cylinders. The fuel pump has difficulty purging vapor in the pump and fuel lines. When the engine is shutdown after a flight, it's hot, which allows heat to draw into the fuel lines including the fuel pump and vapor can form.
 
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I posted in Sarah's other thread, but do you think maybe some fuel line insulation or a heat shield is missing? For vapor lock to form in flight like that, I would think somehow the fuel is getting hotter than it is supposed to.
 
80"degrees doesn't seem hot enough. Full disclosure, my only experience with vapor lock involved a Volkswagen Bug and temps well over 100 F.
 
Well I appreciate the thoughts..hoping with some more checks tmr I can rule out anything major and I wont feel so scared flying away from the airport..
 
Yeah, with work done on the servo very recently, I'd want a second set of eyeballs looking over the system to see if that work was done right.
 
Are the injectors clean? I've seen all sorts of things from poor idle, to failed mag checks, to complete loss of power in flight...all caused by clogged up injectors.
 
It doesn't sound like vapor lock, and if it is, something out of the ordinary is causing it, like a misrouted fuel line. I have an SP. I've had vapor lock, but only on the ground in high heat. There's a simple test to rule out vapor lock in the SP: turn on the electric fuel pump. If the problem does not stop, it is not vapor lock. If it does stop, it could be vapor lock, but could also be several other things, like a failing engine-driven fuel pump.
 
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