Mailing List lml@lancaironline.net Message #58434
From: Colyn Case <colyncase@earthlink.net>
Sender: <marv@lancaironline.net>
Subject: Re: [LML] Re: Fuel restriction or air part 2
Date: Tue, 31 May 2011 08:16:54 -0400
To: <lml@lancaironline.net>
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Tom's comment does remind me:  after about 50 hours on my IV-P I noticed one day that the hose insulation going to my gascolator looked ripped.  On closer inspection I determined it had been melted.   Looking around I found no smoke marks but I did determine that the sleeve coupling on the transfer tube was leaking, blowing hot exhaust on the gascolator.

I never had the symptoms you report but I did get a new respect for the integrity of exhaust systems.  (I ended up completely rebuilding mine).

Colyn

On May 25, 2011, at 7:41 AM, TOM GARDINER wrote:

Berni,
 
I am seeing the same symptoms on my aircraft under the same circumstances but without the engine surging.  The fluctuations only last a few seconds before normal pressure and flow is restored.  Turning on the boost pump briefly will clear the symtoms but the issue will return after a few minutes.  My theory is that the fuel is vaporizing in the engine driven pump.  My crossover exhaust runs under the pump and is seperated by about 5 inches.  I am thinking radiation heating from the exhaust is the culprit.  My plan is to put heat shields on the pipes and run an air blast to the pump.  I wll let you know how this works out
 
Tom
 
LNC2 51 hrs  

From: Berni <bbreen@cableone.net>
To: lml@lancaironline.net
Sent: Tue, May 24, 2011 12:23:21 PM
Subject: [LML] Fuel restriction or air part 2

First of all...thanks to everyone that has tried to help me with my engine surge (fuel related) problem on my normally aspirated Lancair IV.  I have throughly checked and tested everything suggested so far.  There are no tank vent issues and a vacuum test of the entire system from the engine driven fuel pump back to the tanks proved there is no air getting into the system.  I even replaced the o rings on the inlet and outlet sides of the electric fuel pump just to be sure.  Unfortunately my test flight this morning confirmed that the issue still remains.

This is what happened.  On a 50 mile cross country where I took off and climbed to 7,500 I experienced zero issues.  I landed took on some fuel and took off for home.  I climbed to 7,500 again and saw that the fuel flow and fuel pressure gauges were fluctuating.  Since this occurrence preferred my engine surge problem in the past I knew it was coming and it did.  The engine began surging and continued to do so until I turned on the electric ( back up) fuel pump.  The engine and gauge readings stabilized immediately.

So this is where I am...I know I do not have any vacuum (air) leaks from the tanks through to the engine driven pump, nor do I have any restrictions in the fuel lines or fuel tank vents.  I have replaced my engine driven pump.  All symptoms remain.

Question...if I am at cruise settings and leaned out reading 16GPH on the fuel flow and 10PSI on the fuel pressure should this readings rise when I turn the electric fuel pump on?  My GPH goes from 16 to 21 and my fuel pressure goes from 10 to 15 or higher.

Sent from my iPad
Berni Breen
Bbreen@cableone.net
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