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Fuel line testing

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rvdave

Joined: 24 Jan 2009
Posts: 191

Posted: Tue Sep 05, 2017 5:30 pm Post subject: Fuel line testing

Getting ready to pressurize from fuel servo back to wing root testing for leaks. Should there be any concern about pressurizing backwards through mechanical and electric fuel pump? Don't want to blow a diaphragm or whatever the configuration is in there.

_________________
Dave Ford
Cadillac, MI

philperry9

Joined: 23 Nov 2011
Posts: 381

Posted: Tue Sep 05, 2017 8:28 pm Post subject: Fuel line testing

I don't think there really is a concern, but I chose to test by vacuum.  



One thing I'd mention is that me fuel valve is going to leak by in the body between your right and left tanks.  When it's flowing fuel and operating near neutral pressures, it will seal up. But when you put pressure (or vacuum on it) it will leak by the seals/o-rings internally.   Took me a while to figure that out.  



I'd suggest testing segments as opposed to the whole thing because of the complexity of the fuel valve leaking.  But it can be done as long as you're ready for it.  





Sent from my iPhone



 	  Quote: 	
		   On Sep 5, 2017, at 8:30 PM, rvdave <rv610dave(at)gmail.com> wrote:

 

 

 

 Getting ready to pressurize from fuel servo back to wing root testing for leaks. Should there be any concern about pressurizing backwards through mechanical and electric fuel pump? Don't want to blow a diaphragm or whatever the configuration is in there.

 

 --------

 Dave Ford

 RV6 for sale

 RV10 building

 Cadillac, MI

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=472535#472535

Kelly McMullen

Joined: 16 Apr 2008
Posts: 1188
Location: Sun Lakes AZ

Posted: Tue Sep 05, 2017 9:09 pm Post subject: Fuel line testing

Phil,

Did you get your engine running smoothly again?

-sent from the I-droid implanted in my forearm

On Tue, Sep 5, 2017 at 9:27 PM, Phillip Perry <philperry9(at)gmail.com (philperry9(at)gmail.com)> wrote:

 	  Quote: 	
		  --> RV10-List message posted by: Phillip Perry <philperry9(at)gmail.com (philperry9(at)gmail.com)>

 I don't think there really is a concern, but I chose to test by vacuum.

 One thing I'd mention is that me fuel valve is going to leak by in the body between your right and left tanks.Â  When it's flowing fuel and operating near neutral pressures, it will seal up. But when you put pressure (or vacuum on it) it will leak by the seals/o-rings internally.Â  Â Took me a while to figure that out.

 I'd suggest testing segments as opposed to the whole thing because of the complexity of the fuel valve leaking.Â  But it can be done as long as you're ready for it.

 Sent from my iPhone

 > On Sep 5, 2017, at 8:30 PM, rvdave <rv610dave(at)gmail.com (rv610dave(at)gmail.com)> wrote:

 >

 > --> RV10-List message posted by: "rvdave" <rv610dave(at)gmail.com (rv610dave(at)gmail.com)>

 >

 > Getting ready to pressurize from fuel servo back to wing root testing for leaks. Should there be any concern about pressurizing backwards through mechanical and electric fuel pump? Don't want to blow a diaphragm or whatever the configuration is in there.

 >

 > --------

 > Dave Ford

 > RV6 for sale

 > RV10 building

 > Cadillac, MI

 >

 >

 >

 >

 > Read this topic online here:

 >

 > http://forums.matronics.com/viewtopic.php?p=472535#472535

 >

 >

 >

 >

 >

 >

 >

 >

 >

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_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor
KCHD

philperry9

Joined: 23 Nov 2011
Posts: 381

Posted: Tue Sep 05, 2017 9:29 pm Post subject: Fuel line testing

Hope to have a final report over the next day or so.   I've been absent for about 3 weeks dealing with a death in the family and then right back down to Houston making trips post Harvey to get my parents out, and back, and out, back to get setup again too. 

I made a flight today that really looked good.   Hope to confirm some if it in the next day or so and then once I know it's good I'll claim victory.    

Sent from my iPhone

On Sep 6, 2017, at 12:07 AM, Kelly McMullen <apilot2(at)gmail.com (apilot2(at)gmail.com)> wrote:

 	  Quote: 	
		  Phil,

Did you get your engine running smoothly again?

-sent from the I-droid implanted in my forearm

On Tue, Sep 5, 2017 at 9:27 PM, Phillip Perry <philperry9(at)gmail.com (philperry9(at)gmail.com)> wrote:

 	  Quote: 	
		  --> RV10-List message posted by: Phillip Perry <philperry9(at)gmail.com (philperry9(at)gmail.com)>

 I don't think there really is a concern, but I chose to test by vacuum.

 One thing I'd mention is that me fuel valve is going to leak by in the body between your right and left tanks.  When it's flowing fuel and operating near neutral pressures, it will seal up. But when you put pressure (or vacuum on it) it will leak by the seals/o-rings internally.   Took me a while to figure that out.

 I'd suggest testing segments as opposed to the whole thing because of the complexity of the fuel valve leaking.  But it can be done as long as you're ready for it.

 Sent from my iPhone

 > On Sep 5, 2017, at 8:30 PM, rvdave <rv610dave(at)gmail.com (rv610dave(at)gmail.com)> wrote:

 >

 > --> RV10-List message posted by: "rvdave" <rv610dave(at)gmail.com (rv610dave(at)gmail.com)>

 >

 > Getting ready to pressurize from fuel servo back to wing root testing for leaks. Should there be any concern about pressurizing backwards through mechanical and electric fuel pump? Don't want to blow a diaphragm or whatever the configuration is in there.

 >

 > --------

 > Dave Ford

 > RV6 for sale

 > RV10 building

 > Cadillac, MI

 >

 >

 >

 >

 > Read this topic online here:

 >

 > http://forums.matronics.com/viewtopic.php?p=472535#472535

 >

 >

 >

 >

 >

 >

 >

 >

 >

 ====================================

 -List" rel="noreferrer" target="_blank">http://www.matronics.com/Navigator?RV10-List

 ====================================

  FORUMS -

 eferrer" target="_blank">http://forums.matronics.com

 ====================================

 WIKI -

 errer" target="_blank">http://wiki.matronics.com

 ====================================

 b Site -

           -Matt Dralle, List Admin.

 rel="noreferrer" target="_blank">http://www.matronics.com/contribution

 ====================================

rvdave

Joined: 24 Jan 2009
Posts: 191

Posted: Fri Sep 08, 2017 5:51 am Post subject: Re: Fuel line testing

""One thing I'd mention is that me fuel valve is going to leak by in the body between your right and left tanks. When it's flowing fuel and operating near neutral pressures, it will seal up. But when you put pressure (or vacuum on it) it will leak by the seals/o-rings internally. Took me a while to figure that out"". 



Ok, so I'm pressurizing at the wing root, capped before going into fuel servo, have the afp purge valve outlet plugged and I am showing a leak / won't hold pressure,  but can't find any fittings leaking with bubble test.  Could my stock fuel valve be leaking ?  Even if it was all outlets are capped so should hold pressure?  Puzzled

_________________
Dave Ford
Cadillac, MI

philperry9

Joined: 23 Nov 2011
Posts: 381

Posted: Fri Sep 08, 2017 6:05 am Post subject: Fuel line testing

Lol.   You're right where I was when I tried it too.   Head scratching.  



Are you capped at both tanks?



Sent from my iPhone



 	  Quote: 	
		   On Sep 8, 2017, at 8:51 AM, rvdave <rv610dave(at)gmail.com> wrote:

 

 

 

 ""One thing I'd mention is that me fuel valve is going to leak by in the body between your right and left tanks. When it's flowing fuel and operating near neutral pressures, it will seal up. But when you put pressure (or vacuum on it) it will leak by the seals/o-rings internally. Took me a while to figure that out"". 

 

 Ok, so I'm pressurizing at the wing root, capped before going into fuel servo, have the afp purge valve outlet plugged and I am showing a leak / won't hold pressure,  but can't find any fittings leaking with bubble test.  Could my stock fuel valve be leaking ?  Even if it was all outlets are capped so should hold pressure?  Puzzled

 

 --------

 Dave Ford

 RV6 for sale

 RV10 building

 Cadillac, MI

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=472612#472612

rvdave

Joined: 24 Jan 2009
Posts: 191

Posted: Fri Sep 08, 2017 7:43 am Post subject: Re: Fuel line testing

Yes capped before entering tanks at wing root.  I have a tee on right line forward to purge valve.  Introducing air at right wing root.  AFP pump after fuel valve, capped line at exit of purge valve, capped line at entrance line before servo.  Funny thing is sometimes it appears to be a fast leak down and other times a slow leak down.  Your explanation of fuel valve makes sense but can't prove it yet.  No leak at stem of valve or nut  of valve.  Maybe afp pump or mech pump leak ?  Still looking.

_________________
Dave Ford
Cadillac, MI

philperry9

Joined: 23 Nov 2011
Posts: 381

Posted: Fri Sep 08, 2017 8:12 am Post subject: Fuel line testing

I think you're on the right track.  Checking me stem on the valve and bypass valve is a good idea.  



Also checking the two pumps and the body seams on them might be good too.  



Not sure about the PSI sensor, but it might have something goofy going on there too.  



I found that it was impossible to test the entire system, but broke it down and had to check each leg from the fuel valve in segments.



I could prove the left side was tight.  The right side was tight.   The forward part was tight (capped at the inlet of the mechanical fuel pump).  



When you put it all together the results were inconsistent.  Using my hand vacuum pump and gauge, I was able to determine that it didn't take much more than 2-3 inches of suction to suck open the o-rings/seals inside the valve.  At 5 it was really moving fuel.  



That valve has isn't really designed to have pressures on it, it's just designed to provide a path from the tank forward. 



Phil



Sent from my iPhone



 	  Quote: 	
		   On Sep 8, 2017, at 10:43 AM, rvdave <rv610dave(at)gmail.com> wrote:

 

 

 

 Yes capped before entering tanks at wing root.  I have a tee on right line forward to purge valve.  Introducing air at right wing root.  AFP pump after fuel valve, capped line at exit of purge valve, capped line at entrance line before servo.  Funny thing is sometimes it appears to be a fast leak down and other times a slow leak down.  Your explanation of fuel valve makes sense but can't prove it yet.  No leak at stem of valve or nut  of valve.  Maybe afp pump or mech pump leak ?  Still looking.

 

 --------

 Dave Ford

 RV6 for sale

 RV10 building

 Cadillac, MI

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=472625#472625

rvdave

Joined: 24 Jan 2009
Posts: 191

Posted: Fri Sep 08, 2017 2:24 pm Post subject: Re: Fuel line testing

I have confirmed that the leak/pressure drop is isolated to the afp purge valve itself so I'm not sure how tight this is suppose to be internally.  Seems like in ico position there should be no flow to spider but maybe it reacts differently to fuel rather than air?

_________________
Dave Ford
Cadillac, MI

philperry9

Joined: 23 Nov 2011
Posts: 381

Posted: Fri Sep 08, 2017 2:56 pm Post subject: Fuel line testing

How much pressure are you putting on the line?



Sent from my iPhone



 	  Quote: 	
		   On Sep 8, 2017, at 5:24 PM, rvdave <rv610dave(at)gmail.com> wrote:

 

 

 

 I have confirmed that the leak/pressure drop is isolated to the afp purge valve itself so I'm not sure how tight this is suppose to be internally.  Seems like in ico position there should be no flow to spider but maybe it reacts differently to fuel rather than air?

 

 --------

 Dave Ford

 RV6 for sale

 RV10 building

 Cadillac, MI

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=472670#472670

rvdave

Joined: 24 Jan 2009
Posts: 191

Posted: Fri Sep 08, 2017 3:18 pm Post subject: Re: Fuel line testing

50 psi but it bleeds down to 0

_________________
Dave Ford
Cadillac, MI

philperry9

Joined: 23 Nov 2011
Posts: 381

Posted: Fri Sep 08, 2017 3:54 pm Post subject: Fuel line testing

Yeah that's way too much.  That valve is basically a hole that rotates around inside a cylinder and is sealed with o-rings.   50 psi will push those o-rings right out of the way. 



I don't recall what the psi is forward of the servo, but I seem to recall its very low.   The spider (iirc) operates with a series of check valves that are normally closed and they only open when the cylinder on the intake stroke sucks them open.   Then they close.    That way fuel can be kept at the spider but it's sucked into the proper cylinder.  I might be over simplifying that, and others can correct me.   But that's how I seem to recall it working.  



So 50 psi on the back side of the spider would just spray fuel down all the lines at the same time.   So it pretty sure 50psi is way too high.  



Try dialing it down to something like 2 lbs (if you can) and see what you get.    I suspect you will find that the leak stops once you get down to a lower pressure.  



If you can't do that, try putting your thumb over one side, sucking a vacuum through it, and plugging it with your tongue to see if it holds. 



You can generate enough suction to suck open the o-rings with your mouth.   But you can prove it seals.  



Sent from my iPhone



 	  Quote: 	
		   On Sep 8, 2017, at 6:18 PM, rvdave <rv610dave(at)gmail.com> wrote:

 

 

 

 50 psi

 

 --------

 Dave Ford

 RV6 for sale

 RV10 building

 Cadillac, MI

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=472675#472675

rvdave

Joined: 24 Jan 2009
Posts: 191

Posted: Fri Sep 08, 2017 4:02 pm Post subject: Re: Fuel line testing

Thanks for the info, that's probably why I saw a variance in the bleed down, I'll try lower pressure and see how that goes tomorrow.

_________________
Dave Ford
Cadillac, MI

Kellym

Joined: 10 Jan 2006
Posts: 1705
Location: Sun Lakes AZ

Posted: Fri Sep 08, 2017 5:11 pm Post subject: Fuel line testing

The input to the fuel servo is 15-30 psi. The output to the fuel flow 

divider is somewhere between 5 and 10 psi. When the fuel pressure drops 

below 4 psi there is a valve in the flow divider that closes to enable 

full idle cutoff. The intake valve opening has nothing to do with the 

delivery of fuel to the injector. Our injectors are continuous flow, and 

all that varies is the amount of fuel delivered. The fuel pressure the 

servo delivers to the flow divider determines the rate of fuel delivered 

to the intake manifold. The injector nozzle atomizes the fuel, which 

then hopefully vaporizes for uniform delivery into the cylinder.

Certainly the purge valve should withstand up to 15 psi of fuel 

pressure. Air pressure is a different animal. If the purge valve doesn't 

leak with the engine running, it isn't the problem. You could fasten a 

paper towel around the valve outlet, then don't purge at shut down. If 

there are any fuel stains on the paper towel, it leaks.

On 9/8/2017 4:52 PM, Phillip Perry wrote:

 	  Quote: 	

 Yeah that's way too much.  That valve is basically a hole that rotates around inside a cylinder and is sealed with o-rings.   50 psi will push those o-rings right out of the way.

 I don't recall what the psi is forward of the servo, but I seem to recall its very low.   The spider (iirc) operates with a series of check valves that are normally closed and they only open when the cylinder on the intake stroke sucks them open.   Then they close.    That way fuel can be kept at the spider but it's sucked into the proper cylinder.  I might be over simplifying that, and others can correct me.   But that's how I seem to recall it working.

 So 50 psi on the back side of the spider would just spray fuel down all the lines at the same time.   So it pretty sure 50psi is way too high.

 Try dialing it down to something like 2 lbs (if you can) and see what you get.    I suspect you will find that the leak stops once you get down to a lower pressure.

 If you can't do that, try putting your thumb over one side, sucking a vacuum through it, and plugging it with your tongue to see if it holds.

 You can generate enough suction to suck open the o-rings with your mouth.   But you can prove it seals.

 Sent from my iPhone

> On Sep 8, 2017, at 6:18 PM, rvdave <rv610dave(at)gmail.com> wrote:

>

> 

>

> 50 psi

>

> --------

> Dave Ford

> RV6 for sale

> RV10 building

> Cadillac, MI

>

>

> Read this topic online here:

>

> http://forums.matronics.com/viewtopic.php?p=472675#472675

>

_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
KCHD

philperry9

Joined: 23 Nov 2011
Posts: 381

Posted: Fri Sep 08, 2017 6:24 pm Post subject: Fuel line testing

Back at the house where I can check the AFP flow divider manual.Â  It doesn't sound like there's much pressure on the spider (or valve) from their description. Â  I scanned for an exact number, but 1.75-3 PSI is the best I could find.



Needless to say, I'd check with with a much smaller amount of pressure. Â Â 

Is the engine running or is this still in a new build? Â  If it's a new build, I'd just check what you can check and work on the assumptions that the valves are behaving as designed until they really do exhibit a problem and warrant going down the rabbit hole of diagnosing a leak that may not exist.

Phil

        

FLOW DIVIDERÂ  

1-7. Metered fuel is delivered from the fuel controller to the flow divider. It's purpose is to divide the metered fuel equally to each injection nozzle at idle regardless of their height between each other. At idle, nozzle back pressure is typically 1-5 inches of gas pressure, if there is a difference in height between the nozzles then idle flow will tend to flow out the lowest nozzles. Metered fuel pressure enters the flow divider through a channel that permits fuel to pass through the I.D. of the flow divider spool valve. At idle the fuel pressure from the fuel controller must build up to overcome the spring force applied to the diaphragm and spool valve. This moves the spool valve upward to allow fuel to pass through the calibrated slots in the bottom of the flow divider bushing. Since the fuel controller meters and delivers a fixed amount of fuel to the flow divider, the spool valve will only open as far as necessary to pass the amount of fuel to the nozzles. Since it takes approximately 1.75-3 PSI pressure to open the spool valve, the fuel will accurately be divided between the nozzles if there is a difference in height between them of 70 inches. At idle the nozzle discharge pressure is negligible, the opening of the spool valve to the slots is very small, and thus the fuel is divided for the individual cylinders at this point by the flow divider. The flow divider also keeps the metered fuel under pressure and shuts off the individual nozzle ports when the fuel controller is placed in "idle cutoff".Â 





On Fri, Sep 8, 2017 at 7:20 PM, Kelly McMullen <kellym(at)aviating.com (kellym(at)aviating.com)> wrote:

 	  Quote: 	
		  --> RV10-List message posted by: Kelly McMullen <kellym(at)aviating.com (kellym(at)aviating.com)>

 

 The input to the fuel servo is 15-30 psi. The output to the fuel flow divider is somewhere between 5 and 10 psi. When the fuel pressure drops below 4 psi there is a valve in the flow divider that closes to enable full idle cutoff. The intake valve opening has nothing to do with the delivery of fuel to the injector. Our injectors are continuous flow, and all that varies is the amount of fuel delivered. The fuel pressure the servo delivers to the flow divider determines the rate of fuel delivered to the intake manifold. The injector nozzle atomizes the fuel, which then hopefully vaporizes for uniform delivery into the cylinder.

 Certainly the purge valve should withstand up to 15 psi of fuel pressure. Air pressure is a different animal. If the purge valve doesn't leak with the engine running, it isn't the problem. You could fasten a paper towel around the valve outlet, then don't purge at shut down. If there are any fuel stains on the paper towel, it leaks.

 

 On 9/8/2017 4:52 PM, Phillip Perry wrote:

  	  Quote: 	
		   --> RV10-List message posted by: Phillip Perry <philperry9(at)gmail.com (philperry9(at)gmail.com)>

 

 Yeah that's way too much.Â  That valve is basically a hole that rotates around inside a cylinder and is sealed with o-rings.Â  Â 50 psi will push those o-rings right out of the way.

 

 I don't recall what the psi is forward of the servo, but I seem to recall its very low.Â  Â The spider (iirc) operates with a series of check valves that are normally closed and they only open when the cylinder on the intake stroke sucks them open.Â  Â Then they close.Â  Â  That way fuel can be kept at the spider but it's sucked into the proper cylinder.Â  I might be over simplifying that, and others can correct me.Â  Â But that's how I seem to recall it working.

 

 So 50 psi on the back side of the spider would just spray fuel down all the lines at the same time.Â  Â So it pretty sure 50psi is way too high.

 

 Try dialing it down to something like 2 lbs (if you can) and see what you get.Â  Â  I suspect you will find that the leak stops once you get down to a lower pressure.

 

 If you can't do that, try putting your thumb over one side, sucking a vacuum through it, and plugging it with your tongue to see if it holds.

 

 You can generate enough suction to suck open the o-rings with your mouth.Â  Â But you can prove it seals.

 

 

 

 Sent from my iPhone

 

  	  Quote: 	
		   On Sep 8, 2017, at 6:18 PM, rvdave <rv610dave(at)gmail.com (rv610dave(at)gmail.com)> wrote:

 

 --> RV10-List message posted by: "rvdave" <rv610dave(at)gmail.com (rv610dave(at)gmail.com)>

 

 50 psi

 

 --------

 Dave Ford

 RV6 for sale

 RV10 building

 Cadillac, MI

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=472675#472675

 

 

 

 

 

 

 

 

 

 	
 

 

 

 

 	
 ====================================

 -List" rel="noreferrer" target="_blank">http://www.matronics.com/Navigator?RV10-List

 ====================================

  FORUMS -

 eferrer" target="_blank">http://forums.matronics.com

 ====================================

 WIKI -

 errer" target="_blank">http://wiki.matronics.com

 ====================================

 b Site -

 Â  Â  Â  Â  Â  -Matt Dralle, List Admin.

 rel="noreferrer" target="_blank">http://www.matronics.com/contribution

 ====================================

Kelly McMullen

Joined: 16 Apr 2008
Posts: 1188
Location: Sun Lakes AZ

Posted: Fri Sep 08, 2017 8:15 pm Post subject: Fuel line testing

Phil,



The pressures discussed above are for engine idle and idle cutoff. They are significantly higher when you are using substantial power. They are saying the spool valve is likely to close at anything less than 3 psi to achieve idle cutoff.



-sent from the I-droid implanted in my forearm

 

On Fri, Sep 8, 2017 at 7:22 PM, Phillip Perry <philperry9(at)gmail.com (philperry9(at)gmail.com)> wrote:

 	  Quote: 	
		  Back at the house where I can check the AFP flow divider manual.Â  It doesn't sound like there's much pressure on the spider (or valve) from their description. Â  I scanned for an exact number, but 1.75-3 PSI is the best I could find.



Needless to say, I'd check with with a much smaller amount of pressure. Â Â 

Is the engine running or is this still in a new build? Â  If it's a new build, I'd just check what you can check and work on the assumptions that the valves are behaving as designed until they really do exhibit a problem and warrant going down the rabbit hole of diagnosing a leak that may not exist.

Phil

        

FLOW DIVIDERÂ  

1-7. Metered fuel is delivered from the fuel controller to the flow divider. It's purpose is to divide the metered fuel equally to each injection nozzle at idle regardless of their height between each other. At idle, nozzle back pressure is typically 1-5 inches of gas pressure, if there is a difference in height between the nozzles then idle flow will tend to flow out the lowest nozzles. Metered fuel pressure enters the flow divider through a channel that permits fuel to pass through the I.D. of the flow divider spool valve. At idle the fuel pressure from the fuel controller must build up to overcome the spring force applied to the diaphragm and spool valve. This moves the spool valve upward to allow fuel to pass through the calibrated slots in the bottom of the flow divider bushing. Since the fuel controller meters and delivers a fixed amount of fuel to the flow divider, the spool valve will only open as far as necessary to pass the amount of fuel to the nozzles. Since it takes approximately 1.75-3 PSI pressure to open the spool valve, the fuel will accurately be divided between the nozzles if there is a difference in height between them of 70 inches. At idle the nozzle discharge pressure is negligible, the opening of the spool valve to the slots is very small, and thus the fuel is divided for the individual cylinders at this point by the flow divider. The flow divider also keeps the metered fuel under pressure and shuts off the individual nozzle ports when the fuel controller is placed in "idle cutoff".Â 





On Fri, Sep 8, 2017 at 7:20 PM, Kelly McMullen <kellym(at)aviating.com (kellym(at)aviating.com)> wrote:

 	  Quote: 	
		  --> RV10-List message posted by: Kelly McMullen <kellym(at)aviating.com (kellym(at)aviating.com)>

 

 The input to the fuel servo is 15-30 psi. The output to the fuel flow divider is somewhere between 5 and 10 psi. When the fuel pressure drops below 4 psi there is a valve in the flow divider that closes to enable full idle cutoff. The intake valve opening has nothing to do with the delivery of fuel to the injector. Our injectors are continuous flow, and all that varies is the amount of fuel delivered. The fuel pressure the servo delivers to the flow divider determines the rate of fuel delivered to the intake manifold. The injector nozzle atomizes the fuel, which then hopefully vaporizes for uniform delivery into the cylinder.

 Certainly the purge valve should withstand up to 15 psi of fuel pressure. Air pressure is a different animal. If the purge valve doesn't leak with the engine running, it isn't the problem. You could fasten a paper towel around the valve outlet, then don't purge at shut down. If there are any fuel stains on the paper towel, it leaks.

 

 On 9/8/2017 4:52 PM, Phillip Perry wrote:

  	  Quote: 	
		   --> RV10-List message posted by: Phillip Perry <philperry9(at)gmail.com (philperry9(at)gmail.com)>

 

 Yeah that's way too much.Â  That valve is basically a hole that rotates around inside a cylinder and is sealed with o-rings.Â  Â 50 psi will push those o-rings right out of the way.

 

 I don't recall what the psi is forward of the servo, but I seem to recall its very low.Â  Â The spider (iirc) operates with a series of check valves that are normally closed and they only open when the cylinder on the intake stroke sucks them open.Â  Â Then they close.Â  Â  That way fuel can be kept at the spider but it's sucked into the proper cylinder.Â  I might be over simplifying that, and others can correct me.Â  Â But that's how I seem to recall it working.

 

 So 50 psi on the back side of the spider would just spray fuel down all the lines at the same time.Â  Â So it pretty sure 50psi is way too high.

 

 Try dialing it down to something like 2 lbs (if you can) and see what you get.Â  Â  I suspect you will find that the leak stops once you get down to a lower pressure.

 

 If you can't do that, try putting your thumb over one side, sucking a vacuum through it, and plugging it with your tongue to see if it holds.

 

 You can generate enough suction to suck open the o-rings with your mouth.Â  Â But you can prove it seals.

 

 

 

 Sent from my iPhone

 

  	  Quote: 	
		   On Sep 8, 2017, at 6:18 PM, rvdave <rv610dave(at)gmail.com (rv610dave(at)gmail.com)> wrote:

 

 --> RV10-List message posted by: "rvdave" <rv610dave(at)gmail.com (rv610dave(at)gmail.com)>

 

 50 psi

 

 --------

 Dave Ford

 RV6 for sale

 RV10 building

 Cadillac, MI

 

 

 

 

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Kelly McMullen
A&P/IA, EAA Tech Counselor
KCHD

rvdave

Joined: 24 Jan 2009
Posts: 191

Posted: Sat Sep 09, 2017 10:10 am Post subject: Re: Fuel line testing

I've proven that my system does not have leak down pressure unless I hook up purge valve.  I can't find any leaks at inlet or outlet connections so not sure if air is a way to test valve?  I have a message sent to Don at Airflow and will await his reply.

_________________
Dave Ford
Cadillac, MI

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