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  #11  
Old 08-16-2016, 08:25 AM
Mich48041 Mich48041 is offline
 
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Insulating the fuel line going to the pressure sensor will have absolutely no affect on the pressure. The pressure in that fuel line will be equal from end to end, regardless of whether the fuel line contains liquid fuel or fuel vapor or even air. If there were a pressure differential, then that would cause flow which would equalize the pressure.
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  #12  
Old 08-16-2016, 12:25 PM
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WingedFrog WingedFrog is offline
 
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Vapor Locks are more likely with Mogas than with Avgas, furthermore after discussing this with a "refiner", with Mogas vapor locks are more likely with lower Octane fuels. For example 91 Octane is more susceptible than 93 Octane.
After further investigations I believe that the fuel pump failure I thought I had a few months ago on takeoff was likely a vapor lock, result of several factors:
- I had switched from 93 Octane Ethanol Free to 91 as the 93 Ethanol free had disappeared from Service Stations in my area
- I later found small leaks in my fuel line at the switch off vane and at the red cube that might have resulted in small amount of air sucked in
- ... and aggravating factor (entirely my fault) I did not switch the electric fuel pump before take-off.

The electric fuel pump seems to play an important role in avoiding vapor locks. In my research I found that some old classic cars are subject to vapor locks when operating in high temperature weather. A standard solution to solve this problem is to add an electric pump on the fuel line between the tank and the engine... just like in the RV-12! This fuel pump while helping when "on" could make things worse when "off" as it is introducing a small drag (negative pressure) on the fuel that's pumped by the mechanical fuel pump.

I have not researched the influence of Ethanol on vapor lock but I would not be surprised if ethanol was also a negative factor if it is more volatile than ethanol free mogas.

I would recommend that anyone plagued by suspected vapor locks start by switching to Avgas or to a different source of mogas. Once vapor lock is confirmed you can concentrate on improving the cooling of fuel lines and checking for small leaks. Last I have to admit that VANs strategy of leaving the electric fuel pump on all time was the right thing to do from a safety stand point (if not for a convenient maintenance stand point).
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  #13  
Old 08-16-2016, 03:20 PM
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f1rocket f1rocket is offline
 
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There is (was) a recall by Dynon on faulty fuel pressure sensors. Go to the Dynon website and look for it. My sensor was one that was recalled and once I had it replaced, I no longer have an low fuel pressure issues. Also, it's important to drain and flush this line during the condition inspection per the instructions.
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  #14  
Old 08-17-2016, 04:09 AM
BigJohn BigJohn is offline
 
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Were you using mogas or 100LL?
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  #15  
Old 08-17-2016, 05:46 AM
Chrysopelea Chrysopelea is offline
 
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I was using 91 octane premium (Chevron) in my plane when I experienced this .

I THINK it's non ethanol, but in CA, often there's 10% in gas at pumps..

I was told to use Chevron from a busy station by a number of people.
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  #16  
Old 08-17-2016, 08:57 AM
MMiller MMiller is offline
 
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Quote:
Originally Posted by Chrysopelea View Post
...pulling the electric pump fuse during flight will extend the electric fuel pump's life, ...
You don?t want to remove the fuse to open a circuit. I expect the ATC style fuse holder is rated for less than 50 mating cycles. Looking at the bigger picture, the $50 electric fuel pump will likely outlast the airframe and is less expensive than the Van?s fuse module.

Some data points;
Female Fast-On connectors are rated for 10 mating cycles.
PCB card edge connectors are rated for 50-100 mating cycles
Sub-D connectors are rated for 250-500 mating cycles
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  #17  
Old 08-17-2016, 10:29 AM
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WingedFrog WingedFrog is offline
 
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I forgot to mention in my post to check your supplier of ethanol free Mogas, I found that mine (Sunoco) has a disclaimer about using his Ethanol Free gas in airplanes! I suspect that it is a way to protect themselves as most of their customers for this type of gas are boat and vintage classic cars owners. I do not know if this is true for all suppliers. What this may also mean is that they do not have the same control on the quality of this type of gas as for 100LL Avgas.
As a result I am now back using 93 octane mogas with ethanol.
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  #18  
Old 08-17-2016, 11:04 AM
BigJohn BigJohn is offline
 
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Quote:
Originally Posted by Chrysopelea View Post
I was using 91 octane premium (Chevron) in my plane when I experienced this .

I THINK it's non ethanol, but in CA, often there's 10% in gas at pumps..

I was told to use Chevron from a busy station by a number of people.
I don't want to start a gasoline war here, and I may get flamed for this suggestion, but why don't you try burning 100LL for a few tanks to see if the incident reoccurs?
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  #19  
Old 08-17-2016, 11:06 AM
BigJohn BigJohn is offline
 
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Quote:
Originally Posted by MMiller View Post
You don?t want to remove the fuse to open a circuit. I expect the ATC style fuse holder is rated for less than 50 mating cycles. Looking at the bigger picture, the $50 electric fuel pump will likely outlast the airframe and is less expensive than the Van?s fuse module.

Some data points;
Female Fast-On connectors are rated for 10 mating cycles.
PCB card edge connectors are rated for 50-100 mating cycles
Sub-D connectors are rated for 250-500 mating cycles
That is really interesting information, and good to know. Who does the ratings?
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VAF paid through 10/2019.
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  #20  
Old 08-17-2016, 09:08 PM
RFSchaller RFSchaller is offline
 
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Interesting, but I would think low insertion force would tell you there is a problem. At that time I'd just use some needle nose pliers to squeeze the socket connectors and tighten the fit.
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