---------------------------------------------------------- Engines-List Digest Archive --- Total Messages Posted Sat 11/07/09: 6 ---------------------------------------------------------- Today's Message Index: ---------------------- 0. 12:22 AM - Please Make A Contribution To Support Your Lists (Matt Dralle) 1. 04:28 AM - Re: Air in fuel lines? (jakent@unison.ie) 2. 06:48 AM - Re: Air in fuel lines. (Dennis Holbrook) 3. 11:11 AM - Re: Air in fuel lines. (teamgrumman@aol.com) 4. 04:19 PM - Re: Air in fuel lines. (Jim Aitken) 5. 06:10 PM - Re: Re: Air in fuel lines? (Charlie England) ________________________________ Message 0 _____________________________________ Time: 12:22:30 AM PST US From: Matt Dralle Subject: Engines-List: Please Make A Contribution To Support Your Lists Dear Listers, There is no advertising income to support the Matronics Email Lists and Forums. The operation is supported 100% by your personal Contributions during the November Fund Raiser. Please make your Contribution today to support the continued operation and upgrade of these services. You can pick up a really nice gift for making your Contribution too! You may use a Credit Card or Paypal at the Matronics Contribution Site here: http://www.matronics.com/contribution or, you can send a personal check to the following address: Matronics / Matt Dralle PO Box 347 Livermore, CA 94551-0347 Thank you in advance for your generous support! Matt Dralle Matronics Email List and Forum Administrator ________________________________ Message 1 _____________________________________ Time: 04:28:42 AM PST US From: "jakent@unison.ie" Subject: Engines-List: RE: Air in fuel lines? Subject: Engines-List: Air in fuel lines. Hi all: Been having a lot of trouble with a rough idle problem on my Fuel Injected 0-360 parallel valve engine. I've been going through several tests trying to locate the source of the problem but so far no joy. One suggestion that I have received concerns air getting into the fuel lines. It seems a little far fetched that air could get in through a fitting that is not leaking fuel but I'm running out of ideas so I'll go through and tighten all my fittings to see if that helps. But, that leaves one other possibility and that's air getting in through the fuel selector valve. I'm using the Van's fuel selector that came with my RV-6 kit. It sat in its little brown bag on the shelf in my shop for several years before it got used but seems to working fine. It's not hard to move the selector and its not leaking, at least externally. Anyone experience leaking of this valve or any issue with that might let air into the fuel lines through it? Any ideas on how I might test the valve to see if it's leaking air into the system? I'm using the Van's high pressure pump setup that puts the pump ahead of the selector valve so there will be some suction at the valve. I'm running out of ideas and thinking about switching to a carb. Hate to do that but can't find anything wrong after working on it for the last year, maddening. Thanks. Dean Psiropoulos RV-6A N197DM Hi Dean, Have you checked the air induction system thoroughly for air leaking in at low power settings. A slight tightening of all the hose clips improved things for me. Also you could re-check the idle mixture setting when you are sure the induction leak is not happening? John Kent (EI-DIY RV-4) -------------------------------------------------------------------- mail2web.com Enhanced email for the mobile individual based on Microsoft Exchange - http://link.mail2web.com/Personal/EnhancedEmail ________________________________ Message 2 _____________________________________ Time: 06:48:58 AM PST US From: "Dennis Holbrook" Subject: Re: Engines-List: Air in fuel lines. Dean: Rough idle covers a fairly broad range. My variety of roughness was usually associated with heat and probably best described as a series of 'pauses' in an otherwise smooth idle. I worked with Don Rivera at Airflow Performance who set me up with smaller injectors and a stiffer flow divider spring to increase fuel pressure downstream of the fuel control. Don's theory was simple: heat causes partial vaporization of the fuel... increased pressure decreases vaporization. Worked for me. Dennis RV6/IO360/N54X ________________________________ Message 3 _____________________________________ Time: 11:11:55 AM PST US Subject: Re: Engines-List: Air in fuel lines. From: teamgrumman@aol.com Interesting thing about that air in the fuel line. In the early 90s there were a few Slingsby T-3 Firefly crashes. These pla nes were used by the U.S. Air Force Academy for flight training. The beli ef, at that time, was air in the fuel lines. The Division in which I worked at that time was tasked with determining if there was air in the fuel lines. We built a mock-up of the fuel system and, sure enough, there was air in the fuel lines. Problem solved . . . or so we thought. As it turned out, the air we followed from the pump to the divider disappeared as the air/fuel mixture was sprayed through th e injector nozzle. No big gaps of air sprayed out. Any time a fuel pump pumps, air is separated from the fuel. The only way to keep the air out, is to raise the fuel line pressure above the pressur e at which air separates out. This happens, partly, in the fuel divider. If your engine is carbureted, the float does that; it lets the air vent into the top of the carb. Just for grins, hook up 20 feet or so of clear hose to the outlet of the fuel pump and pump fuel from one wing to the other. LOTs of air. As for the crashes, we speculated the crashes were due to instructors tell ing the new pilots NOT to lean. Why? Jets don't have to be leaned so why teach leaning? Even at the academy's 7200 foot elevation one observer to ld us the planes would cough black smoke while taxiing. -----Original Message----- From: Dennis Holbrook Sent: Sat, Nov 7, 2009 6:48 am Subject: Re: Engines-List: Air in fuel lines. Dean: Rough idle covers a fairly broad range. My variety of roughness was usual ly associated with heat and probably best described as a series of 'pauses' in an otherwise smooth idle. I worked with Don Rivera at Airflow Performance who set me up with smaller injectors and a stiffer flow divider spring to increase fuel pressure downstream of the fuel control. Don's theory was simple: heat causes partial vaporization of the fuel... increased pressur e decreases vaporization. Worked for me. Dennis RV6/IO360/N54X ======================== ============ ======================== ============ ======================== ============ ======================== ============ ________________________________ Message 4 _____________________________________ Time: 04:19:13 PM PST US From: "Jim Aitken" Subject: RE: Engines-List: Air in fuel lines. Then reason that you get air in a fuel line is that the shaft of the fuel selector valve is usually sealed with a single O ring. If the selector shaft is on the suction side of the pump air will be drawn in past the O ring. An O ring is designed to seal with pressure pushing it into a small crevass in a U shaped groove, and it works quite well. The shaft seal will not leak under pressure, which is the normal way to test for leaks, but the O ring will be sucked out of position in a U groove under suction and allow air draw in. The groove for an O ring for negative pressure service is trapezoidal in shape. The Parker O ring catalogue shows this style. The trapezoidal groove is difficult to machine in a narrow hole and probably not considered. An old fashioned packing shaft seal with a compression nut is better for negative pressure. Jim Aitken, P.Eng. -----Original Message----- From: owner-engines-list-server@matronics.com [mailto:owner-engines-list-server@matronics.com] On Behalf Of DEAN PSIROPOULOS Sent: November 6, 2009 9:46 PM Subject: Engines-List: Air in fuel lines. Hi all: Been having a lot of trouble with a rough idle problem on my Fuel Injected 0-360 parallel valve engine. I've been going through several tests trying to locate the source of the problem but so far no joy. One suggestion that I have received concerns air getting into the fuel lines. It seems a little far fetched that air could get in through a fitting that is not leaking fuel but I'm running out of ideas so I'll go through and tighten all my fittings to see if that helps. But, that leaves one other possibility and that's air getting in through the fuel selector valve. I'm using the Van's fuel selector that came with my RV-6 kit. It sat in its little brown bag on the shelf in my shop for several years before it got used but seems to working fine. It's not hard to move the selector and its not leaking, at least externally. Anyone experience leaking of this valve or any issue with that might let air into the fuel lines through it? Any ideas on how I might test the valve to see if it's leaking air into the system? I'm using the Van's high pressure pump setup that puts the pump ahead of the selector valve so there will be some suction at the valve. I'm running out of ideas and thinking about switching to a carb. Hate to do that but can't find anything wrong after working on it for the last year, maddening. Thanks. Dean Psiropoulos RV-6A N197DM ________________________________ Message 5 _____________________________________ Time: 06:10:00 PM PST US From: Charlie England Subject: Re: Engines-List: RE: Air in fuel lines? jakent@unison.ie wrote: > > > Subject: Engines-List: Air in fuel lines. > > > Hi all: > > Been having a lot of trouble with a rough idle problem on my Fuel Injected > 0-360 parallel valve engine. I've been going through several tests trying > to locate the source of the problem but so far no joy. One suggestion that > I have received concerns air getting into the fuel lines. It seems a little > far fetched that air could get in through a fitting that is not leaking fuel > but I'm running out of ideas so I'll go through and tighten all my fittings > to see if that helps. > > But, that leaves one other possibility and that's air getting in through the > fuel selector valve. I'm using the Van's fuel selector that came with my > RV-6 kit. It sat in its little brown bag on the shelf in my shop for several > years before it got used but seems to working fine. It's not hard to move > the selector and its not leaking, at least externally. > > Anyone experience leaking of this valve or any issue with that might let air > into the fuel lines through it? Any ideas on how I might test the valve to > see if it's leaking air into the system? > > I'm using the Van's high pressure pump setup that puts the pump ahead of the > selector valve so there will be some suction at the valve. I'm running out > of ideas and thinking about switching to a carb. Hate to do that but can't > find anything wrong after working on it for the last year, maddening. > Thanks. > > Dean Psiropoulos > RV-6A N197DM > > Hi Dean, > Have you checked the air induction system thoroughly for air leaking in at > low power settings. A slight tightening of all the hose clips improved > things for me. Also you could re-check the idle mixture setting when you > are sure the induction leak is not happening? > John Kent (EI-DIY RV-4) I'd 2nd that thought. I've had the pressed-in intake stubs in the sump get loose, causing bad idle (carb engine, but would cause the same thing with injection). Here's another, somewhat remote possibility. One of my neighbors flies a Cont IO360 Swift. It has a lot of AN hose between the tanks & the fuel pump. It developed the problem of quitting when he would bank at certain angles. 2 or 3 deadstick landings while trying various things to find the problem. He tried a lot of different things & ultimately discovered that if he air-pressurized the suction side AN hose, it would 'blow bubbles' all over the fabric coating if it was wet down with water. (No noticeable gas leaks) He replaced the hoses, & hasn't had it quit since. The best guess is that it was sucking air through the hose sidewalls. (Hose was quite a few years old.) 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