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vaporlock clairfication

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Charles Heathco

Joined: 10 Jan 2006
Posts: 201

Posted: Thu Apr 17, 2008 5:53 am Post subject: vaporlock clairfication

To clarify, re vaporlock, I have a standard carb.  320 150 hp. I had the carb OH, but first had the problem prior to. The lines are  in fire sleve. Charles heathco

   [quote][b]

pitts_pilot(at)bellsouth.
Guest

Posted: Thu Apr 17, 2008 2:41 pm Post subject: vaporlock clairfication

Charles Heathco wrote:

  	  Quote: 	
		              To clarify, re vaporlock, I have a standard carb. 320 150 hp. I had the carb OH, but first had the problem prior to. The lines are in fire sleve. Charles heathco

 	
 Charlie, I missed the original vaporlock post, but will comment anyway so this may be a waste of bandwidth.  I have heard of RVs with vapor lock problems, and am not sure why it happens.  I fly mogas in my Pitts, and even in the summer in FL have never had a smidgen of a problem .... even with fast turn around fuel stops.  The big difference in my installation ..... I have a PS-5 pressure carbureator.  And I don't have any firesleeved hoses in the cowl.  Don't flame me .... I just haven't gotten around to doing it, not that I don't want to do it.

 

 I wish I could figure out the WHY of some mogas vaporlock, but since I don't have the problem ..... I can't fix it.  Maybe we can have some really frank discussion about the problem here and get to the bottom of it. Has anyone cured the problem in another way besides mixing or going to 100LL 100% of the time???

 Linn

 do not archive

 [quote]    	  Quote: 	
		  

	
 [b]

mcculleyja(at)starpower.n
Guest

Posted: Thu Apr 17, 2008 8:10 pm Post subject: vaporlock clairfication

Linn, which type of engine driven fuel pump do you have with the PS-5 

carb--gear type or diaphragm?

Jim

--------------------------------------------------------------------------------------

linn Walters wrote:

 	  Quote: 	
		     Charles Heathco wrote:

> To clarify, re vaporlock, I have a standard carb. 320 150 hp. I had 

> the carb OH, but first had the problem prior to. The lines are in fire 

> sleve. Charles heathco

 Charlie, I missed the original vaporlock post, but will comment anyway 

 so this may be a waste of bandwidth.  I have heard of RVs with vapor 

 lock problems, and am not sure why it happens.  I fly mogas in my Pitts, 

 and even in the summer in FL have never had a smidgen of a problem .... 

 even with fast turn around fuel stops.  The big difference in my 

 installation ..... I have a PS-5 pressure carbureator.  And I don't have 

 any firesleeved hoses in the cowl.  Don't flame me .... I just haven't 

 gotten around to doing it, not that I don't want to do it.

 I wish I could figure out the WHY of some mogas vaporlock, but since I 

 don't have the problem ..... I can't fix it.  Maybe we can have some 

 really frank discussion about the problem here and get to the bottom of 

 it. Has anyone cured the problem in another way besides mixing or going 

 to 100LL 100% of the time???

 Linn

 do not archive

-----------------------------------------------------------------------------------------

pitts_pilot(at)bellsouth.
Guest

Posted: Fri Apr 18, 2008 4:38 am Post subject: vaporlock clairfication

J. Mcculley wrote:



 	  Quote: 	
		   



 Linn, which type of engine driven fuel pump do you have with the PS-5 

 carb--gear type or diaphragm? 


	


It's a diaphragm type, but higher pressure ..... 12-15 Lbs if I remember 

right (happening less often).

FWIW, the typical 'vapor lock' occurs when the diaphragm pump tries to 

suck a 'load', creating a lower pressure at the inlet of the pump which 

causes the hot liquid fuel to vaporize.  Once this vapor is in the pump, 

it won't be expelled since the diaphragm just compresses the gas and 

relaxes .... the gas won't open the reed valve because there is higher 

pressure on the outlet.  If you can pressurize the system with another 

pump ..... electrical boost or backup fuel pump ..... then that pump 

should be able to force fresh fuel through the system.  Putting the aux 

fuel pump inside the cabin at the lowest point provides natural head 

pressure (due to gravity) so the electrical pump doesn't cavitate like 

the engine driven one can.  I don't have enough experience to understand 

why injected engines have so much trouble when starting hot.  I guess 

I'm going to get a real education when the -10 is flying!!!

Good question though .... I forgot about my 'different' engine driven pump.

Linn

do not archive



 	  Quote: 	
		  



 Jim

 -------------------------------------------------------------------------------------- 



 linn Walters wrote:



>   Charles Heathco wrote:

>

>> To clarify, re vaporlock, I have a standard carb. 320 150 hp. I had 

>> the carb OH, but first had the problem prior to. The lines are in 

>> fire sleve. Charles heathco

> Charlie, I missed the original vaporlock post, but will comment 

> anyway so this may be a waste of bandwidth.  I have heard of RVs with 

> vapor lock problems, and am not sure why it happens.  I fly mogas in 

> my Pitts, and even in the summer in FL have never had a smidgen of a 

> problem .... even with fast turn around fuel stops.  The big 

> difference in my installation ..... I have a PS-5 pressure 

> carbureator.  And I don't have any firesleeved hoses in the cowl.  

> Don't flame me .... I just haven't gotten around to doing it, not 

> that I don't want to do it.

>

> I wish I could figure out the WHY of some mogas vaporlock, but since 

> I don't have the problem ..... I can't fix it.  Maybe we can have 

> some really frank discussion about the problem here and get to the 

> bottom of it. Has anyone cured the problem in another way besides 

> mixing or going to 100LL 100% of the time???

> Linn

> do not archive



 -----------------------------------------------------------------------------------------

rocketbob(at)gmail.com
Guest

Posted: Fri Apr 18, 2008 8:11 am Post subject: vaporlock clairfication

PS-5C's normally have a vapor return line...  I've got one in my Rocket but its not flying yet.



Regards,

Bob Japundza

RV-6 flying F1 under const.



On Fri, Apr 18, 2008 at 8:37 AM, linn Walters <pitts_pilot(at)bellsouth.net (pitts_pilot(at)bellsouth.net)> wrote:

 [quote]--> RV-List message posted by: linn Walters <pitts_pilot(at)bellsouth.net (pitts_pilot(at)bellsouth.net)> 

 

 J. Mcculley wrote:

 

  	  Quote: 	
		   --> RV-List message posted by: "J. Mcculley" <mcculleyja(at)starpower.net (mcculleyja(at)starpower.net)>

 

 Linn, which type of engine driven fuel pump do you have with the PS-5 carb--gear type or diaphragm? 

 	
 



 It's a diaphragm type, but higher pressure ..... 12-15 Lbs if I remember right (happening less often).

 FWIW, the typical 'vapor lock' occurs when the diaphragm pump tries to suck a 'load', creating a lower pressure at the inlet of the pump which causes the hot liquid fuel to vaporize.  Once this vapor is in the pump, it won't be expelled since the diaphragm just compresses the gas and relaxes .... the gas won't open the reed valve because there is higher pressure on the outlet.  If you can pressurize the system with another pump ..... electrical boost or backup fuel pump ..... then that pump should be able to force fresh fuel through the system.  Putting the aux fuel pump inside the cabin at the lowest point provides natural head pressure (due to gravity) so the electrical pump doesn't cavitate like the engine driven one can.  I don't have enough experience to understand why injected engines have so much trouble when starting hot.  I guess I'm going to get a real education when the -10 is flying!!!

  Good question though .... I forgot about my 'different' engine driven pump.

 Linn

 do not archive



 

  	  Quote: 	
		   

 

 Jim

 -------------------------------------------------------------------------------------- 

 linn Walters wrote:

 

  	  Quote: 	
		     Charles Heathco wrote:

 

  	  Quote: 	
		   To clarify, re vaporlock, I have a standard carb. 320 150 hp. I had the carb OH, but first had the problem prior to. The lines are in fire sleve. Charles heathco

 	
 

 

 Charlie, I missed the original vaporlock post, but will comment anyway so this may be a waste of bandwidth.  I have heard of RVs with vapor lock problems, and am not sure why it happens.  I fly mogas in my Pitts, and even in the summer in FL have never had a smidgen of a problem .... even with fast turn around fuel stops.  The big difference in my installation ..... I have a PS-5 pressure carbureator.  And I don't have any firesleeved hoses in the cowl.  Don't flame me .... I just haven't gotten around to doing it, not that I don't want to do it.

  

 I wish I could figure out the WHY of some mogas vaporlock, but since I don't have the problem ..... I can't fix it.  Maybe we can have some really frank discussion about the problem here and get to the bottom of it. Has anyone cured the problem in another way besides mixing or going to 100LL 100% of the time???

  Linn

 do not archive

 	
 

 ----------------------------------------------------------------------------------------- 

 

 

 

 

 

 	
 

 

 

 

 

 

 



[b]

pitts_pilot(at)bellsouth.
Guest

Posted: Fri Apr 18, 2008 8:40 am Post subject: vaporlock clairfication

Bob J. wrote:

  	  Quote: 	
		  PS-5C's normally have a vapor return line... 	
 It's not really a vapor return line.  It's to return excess fuel to the tank.  The pressure carb is controlled by pressure differentials across various diaphragms, and the inlet bypass controls the actual fuel pressure to the carb.  I suppose that it would vent vapor when pressurized though ..... never had the problem.

 Linn

  	  Quote: 	
		    I've got one in my Rocket but its not flying yet. 	
 Once you get it adjusted correctly ...... it's tedious and you really need the manual ...... it's a good solid carb.  Another  advantage is that the butterfly is upstream of the atomized fuel so you don't have anything to collect carb ice on.

 Linn

 do not archive

 [quote]

   

 Regards,

 Bob Japundza

 RV-6 flying F1 under const.

   

   On Fri, Apr 18, 2008 at 8:37 AM, linn Walters <pitts_pilot(at)bellsouth.net (pitts_pilot(at)bellsouth.net)> wrote:

    	  Quote: 	
		  --> RV-List message posted by: linn Walters <pitts_pilot(at)bellsouth.net (pitts_pilot(at)bellsouth.net)>     

     

 J. Mcculley wrote:

     

      	  Quote: 	
		   --> RV-List message posted by: "J. Mcculley" <mcculleyja(at)starpower.net (mcculleyja(at)starpower.net)>

       

 Linn, which type of engine driven fuel pump do you have with the PS-5 carb--gear type or diaphragm? 

     	
     

     

 It's a diaphragm type, but higher pressure ..... 12-15 Lbs if I remember right (happening less often).

 FWIW, the typical 'vapor lock' occurs when the diaphragm pump tries to suck a 'load', creating a lower pressure at the inlet of the pump which causes the hot liquid fuel to vaporize.  Once this vapor is in the pump, it won't be expelled since the diaphragm just compresses the gas and relaxes .... the gas won't open the reed valve because there is higher pressure on the outlet.  If you can pressurize the system with another pump ..... electrical boost or backup fuel pump ..... then that pump should be able to force fresh fuel through the system.  Putting the aux fuel pump inside the cabin at the lowest point provides natural head pressure (due to gravity) so the electrical pump doesn't cavitate like the engine driven one can.  I don't have enough experience to understand why injected engines have so much trouble when starting hot.  I guess I'm going to get a real education when the -10 is flying!!!

 Good question though .... I forgot about my 'different' engine driven pump.

 Linn

 do not archive          

     

      	  Quote: 	
		         

       

 Jim

 --------------------------------------------------------------------------------------       

 linn Walters wrote:

       

        	  Quote: 	
		    Charles Heathco wrote:

         

          	  Quote: 	
		   To clarify, re vaporlock, I have a standard carb. 320 150 hp. I had the carb OH, but first had the problem prior to. The lines are in fire sleve. Charles heathco

         	
         

         

 Charlie, I missed the original vaporlock post, but will comment anyway so this may be a waste of bandwidth.  I have heard of RVs with vapor lock problems, and am not sure why it happens.  I fly mogas in my Pitts, and even in the summer in FL have never had a smidgen of a problem .... even with fast turn around fuel stops.  The big difference in my installation ..... I have a PS-5 pressure carbureator.  And I don't have any firesleeved hoses in the cowl.  Don't flame me .... I just haven't gotten around to doing it, not that I don't want to do it.

         

 I wish I could figure out the WHY of some mogas vaporlock, but since I don't have the problem ..... I can't fix it.  Maybe we can have some really frank discussion about the problem here and get to the bottom of it. Has anyone cured the problem in another way besides mixing or going to 100LL 100% of the time???

 Linn

 do not archive

       	
       

 -----------------------------------------------------------------------------------------       

       

       

       

       

       

     	
     

     

     

     

     

     

     

     

   

	
 [b]

mcculleyja(at)starpower.n
Guest

Posted: Fri Apr 18, 2008 9:40 am Post subject: vaporlock clairfication

Yes, the PS-5C has a fuel return line to the fuel tank that flows a 

controlled amount of fuel at all times--not just vapor.



The reason I inquired is I have the Lear-Romec gear-type fuel pump that 

is mounted directly to the accessory case with only a typical thin 

gasket. The degree of heat transfer from the accessory case to the pump 

without some form of barrier gasket can cause excessive heating of the 

fuel passing through the pump, particularly at low flow rates (near-idle 

power) after landing.



Operating the upstream electric boost pump (set at a higher pressure) 

delays the vapor formation, but is not the total fix if long duration 

ground operation is involved. Additionally, there is the continuing heat 

transfer into the fuel after shutdown, causing a hot-start problem for 

upwards of 30 minutes later. Operating the boost pump before start 

similar to the procedure in an injected installation is somewhat helpful 

but the rate of return fuel flow is not enough to be very helpful in 

purging and cooling throughout the lines and PS-5C.



My solution was to incorporate a cockpit controlled valve downstream of 

the engine fuel pump to allow additional purging and cooling fuel flow 

through the pump and lines back to the fuel tank, using the electric 

boost pump. This has solved the problem for over 500 hours of operation, 

but I'm glad to now know that the diaphragm type engine pump apparently 

is not subject to the amount of heat absorption as is the gear type.



There are apparently very few Bendix pressure carbs and Lear-Romec pump 

combinations installed in Experimentals.



Jim

------------------------------------------------------------------------------------------ 

Bob J. wrote:

 	  Quote: 	
		   PS-5C's normally have a vapor return line...  I've got one in my Rocket 

 but its not flying yet.

 

 Regards,

 Bob Japundza

 RV-6 flying F1 under const.

 

 On Fri, Apr 18, 2008 at 8:37 AM, linn Walters <pitts_pilot(at)bellsouth.net 

 <mailto:pitts_pilot(at)bellsouth.net>> wrote:

 

     

     <pitts_pilot(at)bellsouth.net <mailto:pitts_pilot(at)bellsouth.net>>

 

 

     J. Mcculley wrote:

 

         

         <mcculleyja(at)starpower.net <mailto:mcculleyja(at)starpower.net>>

 

         Linn, which type of engine driven fuel pump do you have with the

         PS-5 carb--gear type or diaphragm?

 

 

     It's a diaphragm type, but higher pressure ..... 12-15 Lbs if I

     remember right (happening less often).

     FWIW, the typical 'vapor lock' occurs when the diaphragm pump tries

     to suck a 'load', creating a lower pressure at the inlet of the pump

     which causes the hot liquid fuel to vaporize.  Once this vapor is in

     the pump, it won't be expelled since the diaphragm just compresses

     the gas and relaxes .... the gas won't open the reed valve because

     there is higher pressure on the outlet.  If you can pressurize the

     system with another pump ..... electrical boost or backup fuel pump

     ..... then that pump should be able to force fresh fuel through the

     system.  Putting the aux fuel pump inside the cabin at the lowest

     point provides natural head pressure (due to gravity) so the

     electrical pump doesn't cavitate like the engine driven one can.  I

     don't have enough experience to understand why injected engines have

     so much trouble when starting hot.  I guess I'm going to get a real

     education when the -10 is flying!!!

     Good question though .... I forgot about my 'different' engine

     driven pump.

     Linn

     do not archive

 

 

 

 

         Jim

         --------------------------------------------------------------------------------------

 

         linn Walters wrote:

 

              Charles Heathco wrote:

 

                 To clarify, re vaporlock, I have a standard carb. 320

                 150 hp. I had the carb OH, but first had the problem

                 prior to. The lines are in fire sleve. Charles heathco

 

 

 

             Charlie, I missed the original vaporlock post, but will

             comment anyway so this may be a waste of bandwidth.  I have

             heard of RVs with vapor lock problems, and am not sure why

             it happens.  I fly mogas in my Pitts, and even in the summer

             in FL have never had a smidgen of a problem .... even with

             fast turn around fuel stops.  The big difference in my

             installation ..... I have a PS-5 pressure carbureator.  And

             I don't have any firesleeved hoses in the cowl.  Don't flame

             me .... I just haven't gotten around to doing it, not that I

             don't want to do it.

 

             I wish I could figure out the WHY of some mogas vaporlock,

             but since I don't have the problem ..... I can't fix it.

              Maybe we can have some really frank discussion about the

             problem here and get to the bottom of it. Has anyone cured

             the problem in another way besides mixing or going to 100LL

             100% of the time???

             Linn

             do not archive

 

 

         -----------------------------------------------------------------------------------------

 

 

 

 

 

 

 

 

 

 

 

 

 

 * 

 

 

  *

JohnInReno

Joined: 08 Sep 2007
Posts: 150

Posted: Fri Apr 18, 2008 10:15 am Post subject: vaporlock clairfication

Another data point:

 

 STC'd Regular Unleaded Grumman AA1B with O-320 E2D. Auto gas from local high volume Indian reservation with no ethanol. No vapor lock in ~150 hours using mogas about 2/3 of the time.

 

 John Morgensen

 RV9A - fuselage

 

 linn Walters wrote: [quote]       Charles Heathco wrote:

    	  Quote: 	
		                      To clarify, re vaporlock, I have a standard carb. 320 150 hp. I had the carb OH, but first had the problem prior to. The lines are in fire sleve. Charles heathco

   	
 Charlie, I missed the original vaporlock post, but will comment anyway so this may be a waste of bandwidth.  I have heard of RVs with vapor lock problems, and am not sure why it happens.  I fly mogas in my Pitts, and even in the summer in FL have never had a smidgen of a problem .... even with fast turn around fuel stops.  The big difference in my installation ..... I have a PS-5 pressure carbureator.  And I don't have any firesleeved hoses in the cowl.  Don't flame me .... I just haven't gotten around to doing it, not that I don't want to do it.

   

 I wish I could figure out the WHY of some mogas vaporlock, but since I don't have the problem ..... I can't fix it.  Maybe we can have some really frank discussion about the problem here and get to the bottom of it. Has anyone cured the problem in another way besides mixing or going to 100LL 100% of the time???

 Linn

 do not archive

    	  Quote: 	
		        	  Quote: 	
		  

	
   



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 [b]

_________________
John Morgensen
RV-9A - Born on July 3, 2013
RV4 - for sale

JFLEISC(at)aol.com
Guest

Posted: Fri Apr 18, 2008 2:38 pm Post subject: vaporlock clairfication

In a message dated 4/18/2008 12:14:28 P.M. Eastern Daylight Time,  rocketbob(at)gmail.com writes:

  	  Quote: 	
		  PS-5C's    normally have a vapor return line...  I've got one in my Rocket but its    not flying yet.



	


 

 I like that idea but how do you plumb back to the (selected) tank?

  

 Jim

  

 do not archive



Need a new ride? Check out the largest site for U.S. used car listings at AOL Autos.

  [quote][b]

rocketbob(at)gmail.com
Guest

Posted: Fri Apr 18, 2008 5:17 pm Post subject: vaporlock clairfication

 	  Quote: 	
		    I've got one in my Rocket but its not flying yet. 	
 	  Quote: 	
		    Once you get it adjusted correctly ...... it's tedious and you really need the manual ...... it's a good solid carb.  Another  advantage is that the butterfly is upstream of the atomized fuel so you don't have anything to collect carb ice on.

 Linn



	




Mine came off of a friend's 200hp RV-8, the builder took it off after a few hours simply because he didn't want to install a return fuel flow transducer.  It has the red diaphragms and looks like new, and I paid $150.  I have a few Bonanza friends who say they are very trouble-free.  I'll have to get it recalibrated for the 540 but for the price I can't see how I can go wrong with it.

 

Regards,

Bob Japundza

RV-6 flying F1 under const.

do not archive

  [quote][b]

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