Matronics Email Lists :: View topic - Vaporlock issues

Matronics Email Lists
Web Forum Interface to the Matronics Email Lists

Get Email Distribution Too! FAQ Search Memberlist Usergroups Register

Profile Log in to check your private messages Log in

Vaporlock issues - lessons learned
Goto page Previous 1, 2

Matronics Email Lists Forum Index -> Zenith-List

View previous topic :: View next topic

Author Message

601zv(at)ritternet.com
Guest

Posted: Wed Jun 20, 2007 4:27 pm Post subject: Vaporlock issues - lessons learned

As I see it the 601XL plans location for the selector is at a level about 

even with the filler cap on my inboard standard tanks and about the 8-gallon 

level of the outboard tanks, so it's essetially uphill except with full 

fuel. With the selector on the floor it's a a level with about the bottom of 

the inboard tanks, and below the outboard tank bottoms.



---

rge177(at)yahoo.com
Guest

Posted: Wed Jun 20, 2007 6:01 pm Post subject: Vaporlock issues - lessons learned

Gig, 

   If check valves were installed I believe that you

would be able to run a "Both" tank setup.  Wouldn't

the tank, and pump that still have fuel, pressurize

the opposite side up to the check valve?   Think about

this analogy.  Connect two water hoses from different

supply faucets.  The faucets represent both a pump,

and a check valve.  Connect the other ends of the

hoses to a "Y" adapter.  When you turn both faucets

on, you will of course have running water.  Turn one

faucet off, and the other faucet will maintain water

pressure and flow.  The straw and glass analogy is

valid if there are no check valves, and I agree with

you that you certainly want a fuel shut off option.  I

have seen a picture somewhere where someone installed

separate shut off valves for each tank.  Although this

would take a few more seconds to deal with in an

emergency, it would work ok, and probably be a lot

less expensive than some of the valves that we are

currently using.  I guess you could also just use one

simple shut off valve after the "Y" connection of the

lines. 



Ron

Time: 01:06:02 PM PST US

Subject: Re: Vaporlock issues - lessons

learned

From: "Gig Giacona" <wr.giacona(at)suddenlink.net>

This has been discussed and I will say the same thing

I said then.



Get a glass of water and two drinking straws. Put both

straws in your

 mouth. Put

one straw in the water and the other outside the

glass.



Now suck.



The outcome is exactly what will happen if one fuel

tank is empty. 



Time: 01:06:02 PM PST US

Subject: Re: Vaporlock issues - lessons

learned

From: "Gig Giacona" <wr.giacona(at)suddenlink.net>

This has been discussed and I will say the same thing

I said then.



Get a glass of water and two drinking straws. Put both

straws in your

 mouth. Put

one straw in the water and the other outside the

glass.



Now suck.



The outcome is exactly what will happen if one fuel

tank is empty. 

[quote="crvsecretary"]Gentlemen:



 Charles makes a number of very good points here...but

I have a

 question or  two:



 - I'm looking to put a facet pump right at the base

of each tank so

 the  whole

run is pressurized fuel to reduce vapor lock.  Charles

says to be  sure

 the correct

pump is turned on....is there any danger to the facet

pumps by  running

one 'deadheaded' right into the fuel selector...that

way both pumps can

  be wired

to ONE switch to eliminate pilot error.



  - there was a prolific lister here some time ago

that was

  exceptionally knowledgeable

on vapor lock issues.  He suggested eliminating  the

fuel selector

 completely

and running a check valve at the outlet of each  pump.

 That way BOTH

pumps could supply fuel during takeoff and landing and

 ONE pump can

 run during

cruise.  When one pump is running, the check  valve(s)

will eliminate

 crossfeeding

from one tank to another. 





 

Bored stiff? Loosen up... 

Download and play hundreds of games for free on Yahoo! Games.

http://games.yahoo.com/games/front

purplemoon99(at)bellsouth
Guest

Posted: Wed Jun 20, 2007 7:05 pm Post subject: Vaporlock issues - lessons learned

Ken, I was thinking  about the "intermittent" facet fuel pump. As I said 

earlier I dont have a mac. pump all I have is 2 facet inline and 2  separate 

switches..Do you or anyone else have any in put or recommendations  joe 

N101HD   601XL

---

Terry Phillips

Joined: 11 Jan 2006
Posts: 346
Location: Corvallis, MT

Posted: Wed Jun 20, 2007 9:36 pm Post subject: Vaporlock issues - lessons learned

Paul and Doug

1st, Doug's question about fuel flowing from a low spot in the system to a 

pump. Some pumps will move enough air to prime themselves, at least to some 

well defined elevation of the pump above the liquid level. Others will not. 

I think it is usually a tradeoff between pumping efficiency and 

convenience. A self-priming pump will be less efficient, i.e., require more 

power to deliver the fluid at design flow rate. A pump that does not self 

prime can be designed for greater fluid dynamic efficiency, so requires 

less power at design flow rate, but is less convenient to start up.  I 

can't answer whether or not the mechanical fuel pump built into the Jabiru 

is self priming.

2nd, Paul's question about the accumulation of water in a low spot in the 

line. As long as the fuel line diameter is sufficiently small so that the 

fuel is moving with a reasonable velocity, then this should not be a 

problem. The fuel line is 0.25" i.d., if we assume a cruise fuel 

consumption of 5 gph, I calculate a mean flow velocity is 0.55 ft/s. I 

would imagine that a half ft/s would be enough to entrain any water from a 

low spot up to the valve and then on into the gascolator. A bit of water in 

the fuel stream might make the engine hiccup, but it shouldn't be a major 

problem.

The bigger problem occurs if you park your airplane in a cold place in the 

winter. If enough water accumulates at a low point to block the fuel line, 

it would freeze at temperatures below 32 F, and you could not start the 

engine. And the only solution is to warm up the airplane so that the ice 

dam melts. That's an inconvenience, but not a really big deal, since you're 

still on the ground.

Terry

At 04:30 PM 6/20/2007 -0700, you wrote:

 	  Quote: 	
		  At 03:56 PM 6/20/2007, you wrote:

>I am really hoping someone can explain how the fuel would flow uphill to 

>the valve without relying on the system being primed first.  This is 

>something I've been wondering about.

>

>Doug

Perhaps the same way a syphon hose is used to get gas from an auto gas 

tank - by having the fuel pump suck on the line . . .

I am not sure the head of fuel in the tank is lower than the fuel 

switch.  The discussion recently pointed out that there is an uphill bend 

in the fuel line to get to the tank valve mounted near the instrument 

panel.  Considering the wing dihedral it is easy to suspect the fuel will 

actually be above the valve.

It is the intermediate low point in the fuel line that interests me.  I 

wonder if water will accumulate at that point and also whether it even matters.

Paul

XL fuselage

do not archive

Terry Phillips

ttp44~at~rkymtn.net

Corvallis MT

Just starting a 601 kit

_________________
Terry Phillips
Corvallis, MT
ttp44<at>rkymtn.net
Zenith 601XL/Jab 3300 slow build kit - Tail feathers done; working on the wings.

steveadams

Joined: 10 Jan 2006
Posts: 191

Posted: Thu Jun 21, 2007 4:35 am Post subject: Re: Vaporlock issues - lessons learned

Regarding water collecting in a low point in the line. The plans for the CH640 specifically say to ensure that the line from the tank outlet to the selector switch runs slightly "uphill" the whole distance without any low point for water/junk to collect. That way it will either run back into the tank or down to the gascolator where it can be drained off. Once the line is filled with fuel it makes little difference in these installations whether the selector is above or below the tank outlet. The things that determine the overall pressure (or suction) in the line is the fuel line diameter, how many and how tight the bends in the line are, and the difference in height between the tank outlet and the fuel pump. Whether it is 6 inches higher or lower in the middle (fuel selector) will have no significant effect. I've never had any hint of vapor lock, even after having had the plane sit in the sun on the ramp for hours in 95+ temps. As far as water freezing in the line, you could also get a partial blockage that would not be detected on the ground, but starve the engine of fuel at full power, leading to loss of power during the initial climb.



Steve Adams

CH640

lgingell

Joined: 10 Jan 2006
Posts: 50
Location: Lake California Airpark 68CA

Posted: Thu Jun 21, 2007 8:13 am Post subject: Re: Vaporlock issues - lessons learned

I have a XL/Standard 12Gal wing tanks/Andair selector.



I probably already said this in the searchable archives (as did others), but here goes...



Fuel goes from the wings to the Andair selector, which is mounted just above the spar. So fuel is going uphill unless the tanks are full.  Fuel then goes downhill to the ZAC supplied ACS gascolator, onto the fuel flow sensor, and a Facet fuel pump at the base (on) the firewall mounted per instructions at 45 degrees up.  Then up through the firewall to the engine mounted mechanical Jabiru pump.



I use 100LL all the time.  I often wondered about the fuel suck (after reading many posts from 'Frank Hinde' - search the archives..). Anyway, I got vapour lock one time.   The airplane was sitting parked afternoon/overnight on a  hot day in Oregon. Up to 100F.  I couldn't prime the fuel system with the firewall fuel pump as I had vapour lock. Yikes. it took *blowing* in the fuel vents to release this. Try that flying!



Anyway, I don't believe this same condition would likely happen while flying, but I though I should add something soon.



A few flights later, my firewall Facet pump failed.  (Now try starting the engine!)



So,  I did ADD another Facet pump at the left wing root, and seperate switch on the panel for emergency.  This would have solved both issues above (vapour lock and failed pump - which failed open).



When I fly, I prime the system with my firewall elec pump (occasionaly with the other wing root Facet instead - just to test it), for 5 seconds. Turn off. Then start the engine.  



I don't use it for takeoff or landing.  I read of at least one person (Jabriu list) that had a problem where their elec pump (a Facet) caused the engine to quit after takeoff because it overwhelmed the mechanical pump.



I'd rather turn it on in an emergency (and I'd rather not have one of those!).



Also, turning both Facets on in my system will overpower the mechnical pump and fuel sips by and drips out.



..lance

http://lancegingell.com 

Zodiac XL/Jabiru 3300, 185hours

_________________
Zodiac XL/Jab 3300
http://lancegingell.com

ashontz

Joined: 27 Dec 2006
Posts: 723

Posted: Wed Jul 18, 2007 8:10 am Post subject: Re: Vaporlock issues - lessons learned

I'd like to see this setup on paper. Sounds good.



Also, got me thinking about the setup pn my pickup truck, and probably a lot of cars, and that is, there's a feed and a return line to the carb bowl, so basically the fuel just makes a continuous loop from the tank to the carb and overflow back to the tank with the pump positioned at the base of the tank. Not sure what the purpose is but I've never had vapor lock in that old truck (1985).



[quote="crvsecretary"]Gentlemen:

  

 Charles makes a number of very good points here...but I have a question or  two:

  

 - I'm looking to put a facet pump right at the base of each tank so the  whole run is pressurized fuel to reduce vapor lock.  Charles says to be  sure the correct pump is turned on....is there any danger to the facet pumps by  running one 'deadheaded' right into the fuel selector...that way both pumps can  be wired to ONE switch to eliminate pilot error.

  

  - there was a prolific lister here some time ago that was  exceptionally knowledgeable on vapor lock issues.  He suggested eliminating  the fuel selector completely and running a check valve at the outlet of each  pump.  That way BOTH pumps could supply fuel during takeoff and landing and  ONE pump can run during cruise.  When one pump is running, the check  valve(s) will eliminate crossfeeding from one tank to another.  In  addition, by using a 2-gang rotary switch wired Left-Right-Left+Right there is  no way the plane can suffer from NO pumps on due to pilot error.  My only  problem with this setup is that the one fuel pump switch presents a single point  of failure.......

  

 Any thoughts??

  

 Thanks

  

 Tracy Smith

 N458XL (reserved)

 Do Not Archive 

  

  

  

 In a message dated 6/19/2007 12:42:37 PM Eastern Standard Time,  charles.long(at)gm.com writes:

  	  Quote: 	
		  -->    Zenith-List message posted by: charles.long(at)gm.com

  ?      A friend of mine who also flies a Zodie Rocket had an issue    on

takeoff the other day. His engine began to stumble right after liftoff    on a

90 degree day. He immediately cut power and landed. Fortunately he    had

plenty of runway. After assessing the situation, he found that he    had

inadvertently turned on the electric fuel pump at the base of the    wrong

tank. Two lessons to be learned here: ALWAYS USE THE ELECTRIC FUEL    PUMP FOR

BACKUP ON TAKEOFF AND LANDING. SECONDLY, IF USING SEPARATE    ELECTRIC PUMPS

FOR EACH TANK, CONFIRM YOU ARE USING THE RIGHT ONE. This    incident was with

the Rotax 912s using auto fuel. It has been reported that    auto fuel has a

higher vapor lock potential so the electric fuel pumps tend    to be even more

critical for avoiding vapor lock issues. If the pump is at    the base of the

tank, the problem is virtually eliminated since pressurized    fuel won't

vapor lock.



      Before we bad mouth the    912s, I would argue that vapor lock is not an

engine-specific problem. I    also had a vapor lock problem with my Jab

involving a restrictive fuel    filter. The electric pump application

immediately corrected the vapor lock    condition as reported below:

From:  Charles F. Long on    06/20/2005 11:40 AM



To:    Zenith-List Digest List    <zenith>

cc:       micheintz(at)gmail.com

Subject:    Fuel Filter Placement - Lessons    Learned



      I experienced an engine stoppage during    one of my first flights. It

occurred at altitude using cruise power with    the Aux pump off. The engine

immediately restarted after turning the Aux    pump on (windmilling propellor,

so engine starter was not required). I    repeated the stoppage a second time

by shutting the pump off and confirmed    that the Aux pump was required to

keep the engine running. My airplane    configuration is as follows:



      601HDS built from    Kit

      Jabiru 3300A purchased with FWD from ZAC

?        Finger screens in the tank

      Dual Aux    Facet pumps in wing root mounted close to the tank

         Selector valve on the floor just forward of the wing spar

         Single line feeding the Gascolator just aft of the firewall

?        Jabiru Engine fuel pump in series with Aux pumps

         Bosch Metal Can auto fuel filter downstream of the Jab    pump

      Fuel pressure sensor downstream of the Bosch    filter

      Outside air temp - 80 F



  ?      Jabiru recommends installing the fuel filter upstream rather    than

downstream of their fuel pump. I did not follow this practice as I    was

concerned about installing a filter on the suction side of the    pump.



      The fuel system was designed to run at low    pressures (<2 psi). The

Bosch filter may have caused a high enough    pressure drop to induce Vapor

Lock. Fuel flow was tested before the first    flight using the Aux pumps and

flow was confirmed to be over 20 gph. The    test was repeated after this

incident and continued to be over 20 gph. The    flow was never tested using

the Jabiru pump alone. The Jabiru pump was    disassembled and showed no

indications of a problem or    contamination.



      The Bosch filter was discarded and    per the recommendations of those

on the Matronics list, a Flow Ezy    stainless mesh filter (A S & S, p/n

05-28905) was installed upstream of    the Jab pump. The Flow Ezy filter,

though rather expensive (close to $100),    provides high flow/low pressure

drop. This appears to have cured the    problem as I have had no additional

issues after 6 hours additional flight    time. This includes several full

power climbs with Aux pumps    off.



      Looking back on this, I should have used the    high flow, stainless

filter from the get-go. Fortunately, the plane was    designed with fuel pump

redundancy and the Aux pumps were used during    Takeoff and Landing.



      I hesitate to air my dirty    laundry here, but hopefully it will help

some other builders to avoid the    same mistake. CFL

Clear Skies!

Chuck Long, CFI

Zodie    Rocket

N601LE, 110 hr TT

	


 

  



See what's free at AOL.com. 

   	  Quote: 	
		  [b]

bryanmmartin

Joined: 10 Jan 2006
Posts: 1018

Posted: Wed Jul 18, 2007 2:44 pm Post subject: Vaporlock issues - lessons learned

Your truck is probably fuel injected. With fuel injection, the fuel pump 

pressurizes a fuel rail and the pressure is held at at a constant 

setting by a regulator. The regulator bleeds off excess pressure back to 

the tank through the return line. Older carbureted vehicles did not have 

a return line to the tank because they used a lower pressure pump and 

the float valve in the carburetor simply shut off the flow from the pump 

when the bowl was full.



Make sure you include in your design a simple way to shut off all the 

pumps in case of a forced landing.



ashontz wrote:

 	  Quote: 	
		   

 

 I'd like to see this setup on paper. Sounds good.

 

 Also, got me thinking about the setup pn my pickup truck, and probably a lot of cars, and that is, there's a feed and a return line to the carb bowl, so basically the fuel just makes a continuous loop from the tank to the carb and overflow back to the tank with the pump positioned at the base of the tank. Not sure what the purpose is but I've never had vapor lock in that old truck (1985).

 

 [quote="crvsecretary"]Gentlemen:

   

  Charles makes a number of very good points here...but I have a question or  two:

   

  - I'm looking to put a facet pump right at the base of each tank so the  whole run is pressurized fuel to reduce vapor lock.  Charles says to be  sure the correct pump is turned on....is there any danger to the facet pumps by  running one 'deadheaded' right into the fuel selector...that way both pumps can  be wired to ONE switch to eliminate pilot error.

   

   - there was a prolific lister here some time ago that was  exceptionally knowledgeable on vapor lock issues.  He suggested eliminating  the fuel selector completely and running a check valve at the outlet of each  pump.  That way BOTH pumps could supply fuel during takeoff and landing and  ONE pump can run during cruise.  When one pump is running, the check  valve(s) will eliminate crossfeeding from one tank to another.  In  addition, by using a 2-gang rotary switch wired Left-Right-Left+Right there is  no way the plane can suffer from NO pumps on due to pilot error.  My only  problem with this setup is that the one fuel pump switch presents a single point  of failure.......

   

  Any thoughts??

   

-- 
	


Bryan Martin

Zenith 601XL N61BM

Ram Subaru, Stratus redrive

Do Not Archive

_________________
--
Bryan Martin
N61BM, CH 601 XL, Stratus Subaru.
do not archive.

ashontz

Joined: 27 Dec 2006
Posts: 723

Posted: Wed Jul 18, 2007 6:56 pm Post subject: Re: Vaporlock issues - lessons learned

Actually, it's carburated. Odd. Good point about crash landings and being able to turn everything off. I didn't intend to you this system, just a thought. I'm not sure what their thinking was with a pressurized fuel system with a carburated engine.



[quote="bryanmmartin"]Your truck is probably fuel injected. With fuel injection, the fuel pump 

pressurizes a fuel rail and the pressure is held at at a constant 

setting by a regulator. The regulator bleeds off excess pressure back to 

the tank through the return line. Older carbureted vehicles did not have 

a return line to the tank because they used a lower pressure pump and 

the float valve in the carburetor simply shut off the flow from the pump 

when the bowl was full.



Make sure you include in your design a simple way to shut off all the 

pumps in case of a forced landing.



ashontz wrote:

 	  Quote: 	
		   

 

 I'd like to see this setup on paper. Sounds good.

 

 Also, got me thinking about the setup pn my pickup truck, and probably a lot of cars, and that is, there's a feed and a return line to the carb bowl, so basically the fuel just makes a continuous loop from the tank to the carb and overflow back to the tank with the pump positioned at the base of the tank. Not sure what the purpose is but I've never had vapor lock in that old truck (1985).

 

  	  crvsecretary wrote: 	
		  Gentlemen:

   

  Charles makes a number of very good points here...but I have a question or  two:

   

  - I'm looking to put a facet pump right at the base of each tank so the  whole run is pressurized fuel to reduce vapor lock.  Charles says to be  sure the correct pump is turned on....is there any danger to the facet pumps by  running one 'deadheaded' right into the fuel selector...that way both pumps can  be wired to ONE switch to eliminate pilot error.

   

   - there was a prolific lister here some time ago that was  exceptionally knowledgeable on vapor lock issues.  He suggested eliminating  the fuel selector completely and running a check valve at the outlet of each  pump.  That way BOTH pumps could supply fuel during takeoff and landing and  ONE pump can run during cruise.  When one pump is running, the check  valve(s) will eliminate crossfeeding from one tank to another.  In  addition, by using a 2-gang rotary switch wired Left-Right-Left+Right there is  no way the plane can suffer from NO pumps on due to pilot error.  My only  problem with this setup is that the one fuel pump switch presents a single point  of failure.......

   

  Any thoughts??

   

-- 

	


Bryan Martin

Zenith 601XL N61BM

Ram Subaru, Stratus redrive

Do Not Archive

Trainnut01(at)aol.com
Guest

Posted: Thu Jul 19, 2007 2:34 am Post subject: Vaporlock issues - lessons learned

Bryan

 Back in the 70"s there were some carbureted cars that did have a tank  return line specifically to prevent vapor lock. These cars had mechanical fuel  pumps on the engine, and inline fuel filters between the pump and the  carb. That fuel filter had a third, smaller, barb on it that connected to a  fuel tank return line. 

 I worked in both Buick and Oldsmobile shops during that time and I remember  the Oldsmobiles having this setup but I'm not sure about the Buicks. (I Suffer  from CRS)

 Carroll Jernigan



Get a sneak peek of the all-new AOL.com.

  [quote][b]

MaxNr(at)aol.com
Guest

Posted: Thu Jul 19, 2007 11:00 am Post subject: Vaporlock issues - lessons learned

From what I find, if you burn 100LL, your fuel system could be a rip-off of any certified low wing single. When you burn auto-gas, its higher vapor pressure can cause vapor lock. Your truck burns fuel blended for your area and season. Put a winter blend in a plane and climb to altitude and it starts to "boil off" vapor. 100LL has a low vapor pressure. You need to preheat an engine using 100LL in cold weather just to get it started, however your truck starts right up. The typical certified "pressure system" with a single boost pump ahead of the firewall actually sucks fuel from whatever distance from the selected tank. The several sources for auto fuel STC's (Maule, EAA and Peterson Aviation usually require modifications to combat vapor lock. Peterson (http://autofuelstc.com) has a page for homebuilder guidance. Also more info about fuel than you can digest. He suggest boost pumps in or near the tanks to push fuel and vapor through the lines. Of course there is more to it than this. This could be a possible scenario: Flying at altitude on a hot day with autogas in the tanks. You empty one tank and (using your check list to eliminate human error) you select the other tank. One pump is turned off and the other pump is turned on. The bad news is that the pump on the full tank has failed. Empty tank with a good pump and full tank with a bad pump. Your engine driven pump may or may not provide enough suction to overcome any vapor and still feed the engine. If possible, descend or land as soon as practicable. It would be nice to have a LOW FUEL PRES warning light for each pump in addition to the single fuel pressure gauge at the carb. You may not notice the load meter not indicating the draw from the pump. Back when I was "flying for the man" I flew some types that had an interconnect between tanks. You opened a solenoid operated valve and gravity leveled the tanks in a few minutes. Could be done on a 601easily by T ing into the line at each tank and putting a simple valve at the lowest point in the cockpit. But that complicates things. AC 43.13-1B Ch 8, Sec 2 says little about fuel system design. I like a text that went out of print in 1967. Aerospace Propulsion Powerplants by Cargnino has a detailed but dated coverage on fuel systems. (Amazon $1.48 used)

 Do not archive

 Bob 601XL / Lyc O 235 C2C w/ 6.75 to 1 comp ratio- could run on rotgut whiskey

 Do not archive 

**************************************

 Get a sneak peek of the all-new AOL at http://discover.aol.com/memed/aolcom30tour  [quote][b]

bryanmmartin

Joined: 10 Jan 2006
Posts: 1018

Posted: Thu Jul 19, 2007 12:33 pm Post subject: Vaporlock issues - lessons learned

I stand corrected. I don't recall encountering one with this setup.



Trainnut01(at)aol.com wrote:

 	  Quote: 	
		   Bryan

 Back in the 70"s there were some carbureted cars that did have a tank 

 return line specifically to prevent vapor lock. 

 

 

 


	


-- 

Bryan Martin

Zenith 601XL N61BM

Ram Subaru, Stratus redrive

Do Not Archive

_________________
--
Bryan Martin
N61BM, CH 601 XL, Stratus Subaru.
do not archive.

Display posts from previous:

	Matronics Email Lists Forum Index -> Zenith-List	All times are GMT - 8 Hours Goto page Previous 1, 2
Page 2 of 2

Jump to:

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum