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air entering fuel system on suction side - or is my Pierburg

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uuccio(at)gmail.com
Guest

Posted: Sat Jun 21, 2014 11:57 pm Post subject: air entering fuel system on suction side - or is my Pierburg

Hi Folks,



Yesterday was supposed to be my final fuel flow test before taking to the

air again.  I have recently installed a fuel return line in my 912 system

and also a fuel pressure gauge. The a/c is a Kitfox tri-gear, so high-wing

with tanks in each wing and a header tank located behind the seats.  The

fuel flow test was performed on the ground with the aircraft in "take-off"

attitude with tail on the ground (approx 17 degrees).



Previous tests showed  100 l/hr (26 gal/hr) at the exit of the electrical

fuel pump and before the mechanical pump.  This time, to be more realistic,

I measured the fuel flow after the mechanical fuel pump, at the entry of the

4-way junction that goes the carbs and to the fuel return line.  In 18

minutes, the pump put out 18 litres, so 60 l/hr (16 gal/hr), which is still

acceptable, though 40% lower than the first measurement.  But then,

something strange happened: the fuel flow went down dramatically, to approx.

20 l/hr (just over 5 gal/hr).  I checked the gascolator and found it to be

clean.  



A further investigation revealed that the fuel that was being pushed out

contained some air bubbles, which to me means that air must be entering the

fuel circuit on the suction side of the electrical pump.  Or else the

electrical fuel pump is somehow broken and is letting air in.    A further

data point is that if I hook up all the hoses and run the electrical fuel

pump the fuel pressure gauge indicates lower than usual pressure (0.25 bar

instead of 0.45 bar).



So before I go and investigate the suction side of the fuel system I'd like

to ask any experts out there:



1)  Is it possible that I damaged the electrical fuel pump by letting it run

continuously for 20 minutes?    

2)  Is anyone aware of such failure modes for the Pierburg electrical fuel

pump?  

3)  How would you go about investigating the suction side of the fuel

system?   My idea was to disconnect the hose at the exit of the fuel pump

and clamp it closed and then pressurize the circuit between the header tank

and the exit of the electrical fuel pump with an airline and search for

bubbles using soap water.



Thanks in advance for any help... the weather is beautiful flying weather

but I'm grounded until I can sort this out 



Sacha

williamtsullivan(at)att.n
Guest

Posted: Sun Jun 22, 2014 4:27 am Post subject: air entering fuel system on suction side - or is my Pierburg

Sacha- I can think of a couple of things to check before blaming the pump.  First, are the tanks vented?  Are the vents functioning?  Second, make sure that there isn't something blocking the fuel intake.  I had this problem once on a new piece of equipment with a diesel engine.  It would sit and run at full throttle for hours, but if it went down the street it would suck air, and shut the engine down.  It drove us nuts for a while, until we pulled the fuel tank and found a 1" square piece of masking tape drifting around in the fuel.  When it sloshed over to the sucker tube, it blocked it and shut down the engine.  Air in the fuel always makes me think of that.  We found it by pulling the plug at the bottom and trying to drain it.  The fuel would stop running.  Poke a wire in there, and it would run again.  It was invisible when soaked with fuel.  We had to pull the tank to get it out.  The tape had been used to cover all openings when shipped from one

 factory to another, and a piece dropped in when the manufacturer pulled it off.



                                                    Bill Sullivan

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

On Sun, 6/22/14, Sacha <uuccio(at)gmail.com> wrote:



 Subject: air entering fuel system on suction side - or is my Pierburg electrical pump broken?

 To: rotaxengines-list(at)matronics.com

 Date: Sunday, June 22, 2014, 3:56 AM

 

 --> RotaxEngines-List message

 posted by: "Sacha" <uuccio(at)gmail.com>

 

 Hi Folks,

 

 Yesterday was supposed to be my final fuel flow test before

 taking to the

 air again.  I have recently installed a fuel return

 line in my 912 system

 and also a fuel pressure gauge. The a/c is a Kitfox

 tri-gear, so high-wing

 with tanks in each wing and a header tank located behind the

 seats. ----

 

 A further investigation revealed that the fuel that was

 being pushed out

 contained some air bubbles, which to me means that air must

 be entering the

 fuel circuit on the suction side of the electrical

 pump.  

 

 

 RotaxEngines-List Email Forum -

    - MATRONICS WEB FORUMS -

 List Contribution Web Site -

               -Matt

 Dralle, List Admin.

ptag.dev(at)talktalk.net
Guest

Posted: Sun Jun 22, 2014 9:52 am Post subject: air entering fuel system on suction side - or is my Pierburg

Hi! Sacha,

Have you checked the thimble filter in the Pierburg electrical pump?  It

needs a very sharp needle or pointed hooked instrument but only apply it to

the plastic collar and be careful replacing it with a wooden very blunt

pencil pushed home in to place very carefully, do not damage the gauze

filter element because they will NOT supply a replacement .....it would need

an entirely new pump.

Regards

Bob Harrison Europa G-PTAG c/w 914 Rotax and two electric fuel pumps.



--

uuccio(at)gmail.com
Guest

Posted: Mon Jun 23, 2014 10:51 am Post subject: air entering fuel system on suction side - or is my Pierburg

 	  Quote: 	
		   On Jun 22, 2014, at 14:26, william sullivan <williamtsullivan(at)att.net> wrote:

 

 First, are the tanks vented?  Are the vents functioning?  Second, make sure that there isn't something blocking the fuel intake.


	


Thanks Bill. I've been away from the hangar (and email) for a few days but I will check it this week.

uuccio(at)gmail.com
Guest

Posted: Mon Jun 23, 2014 10:52 am Post subject: air entering fuel system on suction side - or is my Pierburg

Bob thank you. I will check it this week. Hopefully I don't need a new pump....



 	  Quote: 	
		   On Jun 22, 2014, at 19:52, "Bob Harrison" <ptag.dev(at)talktalk.net> wrote:

 

 Have you checked the thimble filter in the Pierburg electrical pump?

uuccio(at)gmail.com
Guest

Posted: Tue Jun 24, 2014 7:16 am Post subject: air entering fuel system on suction side - or is my Pierburg

Hi Bill,

I took the header tank off today, emptied and cleaned it.  It had some

silicon gasket material left over from when I installed the fuel level

sender.  Occasionally bits would float around and block the exit orifice and

cause fuel flow to slow down substantially, exactly as you described.  I

expect things will go back to normal as soon as I re-mount the tank.

Thanks again for the help!

Regards,

Sacha

--

williamtsullivan(at)att.n
Guest

Posted: Tue Jun 24, 2014 7:43 am Post subject: air entering fuel system on suction side - or is my Pierburg

Sacha- nice find.  I have also had trouble with Teflon tape.  If you overlap the end of a fitting, it will tear off and clog a filter.  Good luck.

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

On Tue, 6/24/14, Sacha <uuccio(at)gmail.com> wrote:



 Subject: RE: air entering fuel system on suction side - or is my Pierburg electrical pump broken?

 To: rotaxengines-list(at)matronics.com

 Date: Tuesday, June 24, 2014, 11:16 AM

 

 --> RotaxEngines-List message

 posted by: "Sacha" <uuccio(at)gmail.com>

 

 Hi Bill,

 I took the header tank off today, emptied and cleaned

 it.  It had some

 silicon gasket material left over from when I installed the

 fuel level

 sender.  Occasionally bits would float around and block

 the exit orifice and

 cause fuel flow to slow down substantially, exactly as you

 described.  I

 expect things will go back to normal as soon as I re-mount

 the tank.

 Thanks again for the help!

 Regards,

 Sacha

 

 

 --

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Tue Jun 24, 2014 9:05 am Post subject: air entering fuel system on suction side - or is my Pierburg

Silicone seal/products don't get along well with gasoline.

They are not fuel resistant and will cause many fuel related

problems.



john h

mkIII

Rock House, Oregon



--

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

uuccio(at)gmail.com
Guest

Posted: Tue Jun 24, 2014 11:17 am Post subject: air entering fuel system on suction side - or is my Pierburg

Yes indeed. I should have just mounted the sender with the cork gasket that came with it. 



 	  Quote: 	
		   On Jun 24, 2014, at 19:02, "John Hauck" <jhauck(at)elmore.rr.com> wrote:

 

 Silicone seal/products don't get along well with gasoline.

 They are not fuel resistant and will cause many fuel related

 problems.

williamtsullivan(at)att.n
Guest

Posted: Wed Jun 25, 2014 5:26 am Post subject: air entering fuel system on suction side - or is my Pierburg

Sacha- Never use any of the RTV sealants with a cork/rubber gasket.  The RTV will cause the gasket to crumble later on.  I think the solvent in the RTV dissolves the latex.  

                                            Bill Sullivan

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

On Tue, 6/24/14, Sacha <uuccio(at)gmail.com> wrote:

 Subject: Re: air entering fuel system on suction side - or is my Pierburg electrical pump broken?

 To: "rotaxengines-list(at)matronics.com" <rotaxengines-list(at)matronics.com>

 Date: Tuesday, June 24, 2014, 3:17 PM

 --> RotaxEngines-List message

 posted by: Sacha <uuccio(at)gmail.com>

 Yes indeed. I should have just mounted the sender with the

 cork gasket that came with it. 

 > On Jun 24, 2014, at 19:02, "John Hauck" <jhauck(at)elmore.rr.com>

 wrote:

 > 

 > Silicone seal/products don't get along well with

 gasoline.

 > They are not fuel resistant and will cause many fuel

 related

 > problems.

 RotaxEngines-List Email Forum -

    - MATRONICS WEB FORUMS -

 List Contribution Web Site -

               -Matt

 Dralle, List Admin.

uuccio(at)gmail.com
Guest

Posted: Wed Jun 25, 2014 8:41 am Post subject: air entering fuel system on suction side - or is my Pierburg

Bill

Thank you. I'm not sure what RTV is. I used some red stuff which I thought was for engine gaskets. I think Motorsil was the brand. Anyway just to be sure I'll remove it as it serves no useful purpose. 

Sacha

 	  Quote: 	
		   On Jun 25, 2014, at 15:26, william sullivan <williamtsullivan(at)att.net> wrote:

  Sacha- Never use any of the RTV sealants with a cork/rubber gasket.  The RTV will cause the gasket to crumble later on.  I think the solvent in the RTV dissolves the latex.  

                                            Bill Sullivan

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

 On Tue, 6/24/14, Sacha <uuccio(at)gmail.com> wrote:

 Subject: Re: air entering fuel system on suction side - or is my Pierburg electrical pump broken?

 To: "rotaxengines-list(at)matronics.com" <rotaxengines-list(at)matronics.com>

 Date: Tuesday, June 24, 2014, 3:17 PM

 --> RotaxEngines-List message

 posted by: Sacha <uuccio(at)gmail.com>

 Yes indeed. I should have just mounted the sender with the

 cork gasket that came with it. 

>> On Jun 24, 2014, at 19:02, "John Hauck" <jhauck(at)elmore.rr.com>

> wrote:

> 

> Silicone seal/products don't get along well with

 gasoline.

> They are not fuel resistant and will cause many fuel

 related

> problems.

 RotaxEngines-List Email Forum -

    - MATRONICS WEB FORUMS -

 List Contribution Web Site -

               -Matt

 Dralle, List Admin.

williamtsullivan(at)att.n
Guest

Posted: Thu Jun 26, 2014 5:43 am Post subject: air entering fuel system on suction side - or is my Pierburg

RTV stands for "Room Temperature Vulcanizing".  Comes in a tube, and has at least 3 colors- blue, red, and black, indicating useful temperature, and whether or not it cures in the presence of air, or the absence of it.  It is designed to take the place of gaskets, or to skim coat paper ones.  Works great, except on the cork gaskets.  You can find it at an auto parts store.

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

On Wed, 6/25/14, Sacha <uuccio(at)gmail.com> wrote:



 Subject: Re: air entering fuel system on suction side - or is my Pierburg electrical pump broken?

 To: "rotaxengines-list(at)matronics.com" <rotaxengines-list(at)matronics.com>

 Date: Wednesday, June 25, 2014, 12:40 PM

 

 --> RotaxEngines-List message

 posted by: Sacha <uuccio(at)gmail.com>

 

 Bill

 Thank you. I'm not sure what RTV is. I used some red stuff

 which I thought was for engine gaskets. I think Motorsil was

 the brand. Anyway just to be sure I'll remove it as it

 serves no useful purpose. 

 Sacha

 

 > On Jun 25, 2014, at 15:26, william sullivan <williamtsullivan(at)att.net>

 wrote:

 > 

 > 

 sullivan <williamtsullivan(at)att.net>

 > 

 >  Sacha- Never use any of the RTV sealants with a

 cork/rubber gasket.  The RTV will cause the gasket to

 crumble later on.  I think the solvent in the RTV

 dissolves the latex.  

 > 

 >               

                

             Bill Sullivan

 > --------------------------------------------

 > On Tue, 6/24/14, Sacha <uuccio(at)gmail.com>

 wrote:

 > 

 > Subject: Re: air entering fuel

 system on suction side - or is my Pierburg electrical pump

 broken?

 > To: "rotaxengines-list(at)matronics.com"

 <rotaxengines-list(at)matronics.com>

 > Date: Tuesday, June 24, 2014, 3:17 PM

 > 

 > --> RotaxEngines-List message

 > posted by: Sacha <uuccio(at)gmail.com>

 > 

 > Yes indeed. I should have just mounted the sender with

 the

 > cork gasket that came with it. 

 > 

 >>> On Jun 24, 2014, at 19:02, "John Hauck" <jhauck(at)elmore.rr.com>

 >> wrote:

 >> 

 >> Silicone seal/products don't get along well with

 > gasoline.

 >> They are not fuel resistant and will cause many

 fuel

 > related

 >> problems.

 > 

 > 

 > RotaxEngines-List Email Forum -

 >    - MATRONICS WEB FORUMS -

 > List Contribution Web Site -

 >           

    -Matt

 > Dralle, List Admin.

 > 

 > 

 > 

 > 

 > 

 > 

 > 

 > 

 > 

 

 

 RotaxEngines-List Email Forum -

    - MATRONICS WEB FORUMS -

 List Contribution Web Site -

               -Matt

 Dralle, List Admin.

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Thu Jun 26, 2014 6:11 am Post subject: air entering fuel system on suction side - or is my Pierburg

RTV stands for "Room Temperature Vulcanizing".  Comes in a

tube, and has at least 3 colors- blue, red, and black,

indicating useful temperature, and whether or not it cures

in the presence of air, or the absence of it.  It is

designed to take the place of gaskets, or to skim coat paper

ones.  Works great, except on the cork gaskets.  You can

find it at an auto parts store.

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

 



Bill S:



Are all RTV sealants fuel safe?



Are they to be confused with silicone seal?



john h

Rock House, Oregon

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

williamtsullivan(at)att.n
Guest

Posted: Thu Jun 26, 2014 6:37 am Post subject: air entering fuel system on suction side - or is my Pierburg

John- I know that one is fuel resistant- red, I think.  Pretty sure it's silicone seal.  My experience is very limited, so I only remember some of the cautions with the stuff.  I had a friend who bought a used Cadillac with a freshly rebuilt motor.  The cork oil pan gasket dissolved, and cost him an engine rebuild.

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

On Thu, 6/26/14, John Hauck <jhauck(at)elmore.rr.com> wrote:



 Subject: RE: air entering fuel system on suction side - or is my Pierburg electrical pump broken?

 To: rotaxengines-list(at)matronics.com

 Date: Thursday, June 26, 2014, 10:10 AM

 

 --> RotaxEngines-List message

 posted by: "John Hauck" <jhauck(at)elmore.rr.com>

 

 

 

  

   RTV stands for "Room Temperature Vulcanizing". 

 Comes in a

 tube, and has at least 3 colors- blue, red, and black,

 indicating useful temperature, and whether or not it cures

 in the presence of air, or the absence of it.  It is

 designed to take the place of gaskets, or to skim coat

 paper

 ones.  Works great, except on the cork gaskets. 

 You can

 find it at an auto parts store.

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

  

 

 Bill S:

 

 Are all RTV sealants fuel safe?

 

 Are they to be confused with silicone seal?

 

 john h

 Rock House, Oregon

 

 

 

 RotaxEngines-List Email Forum -

    - MATRONICS WEB FORUMS -

 List Contribution Web Site -

               -Matt

 Dralle, List Admin.

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Thu Jun 26, 2014 7:28 am Post subject: air entering fuel system on suction side - or is my Pierburg

John- I know that one is fuel resistant- red, I think.

Pretty sure it's silicone seal.  My experience is very

limited, so I only remember some of the cautions with the

stuff.  I had a friend who bought a used Cadillac with a

freshly rebuilt motor.  The cork oil pan gasket dissolved,

and cost him an engine rebuild.

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

 



Bill S:



Back in 1987, silicone seal caused a low power situation

that put me into the Sebring High School football field.

Had used silicone seal to seal the vent hole in the Ken

Brock seat tank filler cap so I could convert to a vent that

exited the bottom of the aircraft and prevent fuel from

dumping inboard should I go upside down on the ground again.

Tiny balls of silicone seal effectively blocked the valves

in the squeeze bulbs we used to use back then.



john h

mkIII

Rock House, OR

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

williamtsullivan(at)att.n
Guest

Posted: Thu Jun 26, 2014 7:38 am Post subject: air entering fuel system on suction side - or is my Pierburg

I seem to remember that silicone seal (RTV) was being used at automotive factories to replace a lot of gaskets, some time in the 1980's.  Worked great for differential covers, etc.  The biggest problem I ran into was that we weren't sure where, or what type, to use.  Best bet is to bring your glasses to the auto parts store and read all that very tiny print on the packages.  Where I worked, the most common type was blue- we called it "Blue Goo".  Stunk like hell, and hardened in the tube if it sat around for a while.  Maybe Roger or somebody with a lot more practical knowledge can chime in on this.  I was in truck equipment, not automotive.

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

On Thu, 6/26/14, John Hauck <jhauck(at)elmore.rr.com> wrote:



 Subject: RE: air entering fuel system on suction side - or is my Pierburg electrical pump broken?

 To: rotaxengines-list(at)matronics.com

 Date: Thursday, June 26, 2014, 11:28 AM

 

 --> RotaxEngines-List message

 posted by: "John Hauck" <jhauck(at)elmore.rr.com>

 

 

  

   John- I know that one is fuel resistant- red, I

 think.

 Pretty sure it's silicone seal.  My experience is very

 limited, so I only remember some of the cautions with the

 stuff.  I had a friend who bought a used Cadillac with

 a

 freshly rebuilt motor.  The cork oil pan gasket

 dissolved,

 and cost him an engine rebuild.

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

  

 

 Bill S:

 

 Back in 1987, silicone seal caused a low power situation

 that put me into the Sebring High School football field.

 Had used silicone seal to seal the vent hole in the Ken

 Brock seat tank filler cap so I could convert to a vent

 that

 exited the bottom of the aircraft and prevent fuel from

 dumping inboard should I go upside down on the ground

 again.

 Tiny balls of silicone seal effectively blocked the valves

 in the squeeze bulbs we used to use back then.

 

 john h

 mkIII

 Rock House, OR

 

 

 

 RotaxEngines-List Email Forum -

    - MATRONICS WEB FORUMS -

 List Contribution Web Site -

               -Matt

 Dralle, List Admin.

uuccio(at)gmail.com
Guest

Posted: Sat Jun 28, 2014 1:38 pm Post subject: air entering fuel system on suction side - or is my Pierburg

Ok so I got rid of all the silicone sealant and cleaned the cork gasket which seals the VDO sender (it's quite a big gasket with a 40mm diameter hole in the centre and five 5mm holes for the screws around the perimeter). 



Well guess what? The cork seal leaks badly. So I'm back to square one, I need to find a way to seal the VDO sender on the top of my header tank. I have some silicone rubber which I thought of cutting to size and using. What do folks think? 

Another solution would be to use the same red silicone sealant as I used before but only to apply it on the exterior of the tank. I'm concerned it might eat into the cork though as someone (John?) mentioned.

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Sat Jun 28, 2014 2:11 pm Post subject: air entering fuel system on suction side - or is my Pierburg

I would definitely keep silicon sealant away from any fuel

system.



Your silicone coated cork gasket is trash.  Silicone seal

causes the gasket to squeeze out and leak.



You can get several fuel tank sealant cartridges from

Aircraft Spruce that work well.  Also cut your own gasket.



john h

Kolb MKIII

Boise, Idaho



--

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

Roger Lee

Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.

Posted: Sat Jun 28, 2014 4:03 pm Post subject: Re: air entering fuel system on suction side - or is my Pier

Get a new gasket. The buy some Hylomar. This is meant to be used around fuel and will not leak. Do not over use it. I little thin film on each surface will seal just fine.

_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056

ptag.dev(at)tiscali.co.uk
Guest

Posted: Sun Jun 29, 2014 6:05 am Post subject: air entering fuel system on suction side - or is my Pierburg

I recommend you use HYLOMAR sealant made in the USA under licence and

developed by Rolls Royce Aero Engines for all fuel and oil related joints.

But use it very sparingly and especially as mentioned on the instructions.

I would never make any oil or fuel related joint without it.

Regards

Bob Harrison Rolls Royce Aero Engine trained .Europa G-PTAG Rotax 914

--

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