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rotax pulse pump leaking weep hole: UPDATE fixed

 
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Tom Jones



Joined: 12 Mar 2006
Posts: 752
Location: Ellensburg, WA

PostPosted: Sat Jun 16, 2007 11:31 am    Post subject: rotax pulse pump leaking weep hole: UPDATE fixed Reply with quote

The pulse pump on my 503 rotax leaks fuel out the weep hole. It is installed according to the kitfox manual. It is mounted high on the fire wall in a horizontal position with the weep hole on the bottom. I tried a new pump and rerouting the pulse line up over the carb flanges but it did not even slow the amount of fuel leaking. I am using 30R9 rubber fuel injection hose for the pulse line. It l;eaks about 1/2 to 1 ounce per hour of flight.

I asked this question on the Kolb list. They seem to think something is amiss. They don't seem to have this problem Some think the fuel pump diaphram is leaking. I bought a new pump but it does the same. Both pumps I have tried will hold a vacum in the pulse chamber. I am out of ideas on how to fix this.


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Tom Jones
Classic IV
503 Rotax, 72 inch Two blade Warp
Ellensburg, WA


Last edited by Tom Jones on Tue Jun 19, 2007 11:50 am; edited 1 time in total
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dwight purdy



Joined: 10 Feb 2006
Posts: 85

PostPosted: Sun Jun 17, 2007 12:51 am    Post subject: rotax pulse pump leaking weep hole Reply with quote

I think I can help. I had the exact the same problem when I switched from a
532 to a 503. The problem is too long of a pulse line. The port on the 532
and 582 is on the mag end close to the fire wall. On the 503 it is on the
pto end. I moved the pump to the front of the engine mount (still
horizontal) and no more weeping in 460 hours. Someone in the Rotax repair
business suggested this to me.
Dwight Purdy
Model ll
Indiana

At 12:31 PM 6/16/2007 -0700, you wrote:

Quote:


The pulse pump on my 503 rotax leaks fuel out the weep hole. It is
installed according to the kitfox manual. It is mounted high on the fire
wall in a horizontal position with the weep hole on the bottom. I tried a
new pump and rerouting the pulse line up over the carb flanges but it did
not even slow the amount of fuel leaking. I am using 30R9 rubber fuel
injection hose for the pulse line. It l;eaks about 1/2 to 1 ounce per
hour of flight.

I asked this question on the Kolb list. They seem to think something is
amiss. They don't seem to have this problem Some think the fuel pump
diaphram is leaking. I bought a new pump but it does the same. Both
pumps I have tried will hold a vacum in the pulse chamber. I am out of
ideas on how to fix this.

--------
Tom Jones
Classic IV, Phase one
503, Warp
Ellensburg, WA


Read this topic online here:

http://forums.matronics.com/viewtopic.php?p=118753#118753



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dwight
model II
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Tom Jones



Joined: 12 Mar 2006
Posts: 752
Location: Ellensburg, WA

PostPosted: Sun Jun 17, 2007 5:58 am    Post subject: Re: rotax pulse pump leaking weep hole Reply with quote

Quote:
I moved the pump to the front of the engine mount (still
horizontal) and no more weeping in 460 hours.


Thanks Dwight, that makes sense. I'll make the change and test it out when the wind dies down in a couple days.


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Tom Jones
Classic IV
503 Rotax, 72 inch Two blade Warp
Ellensburg, WA
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Float Flyr



Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

PostPosted: Sun Jun 17, 2007 8:38 am    Post subject: rotax pulse pump leaking weep hole Reply with quote

The question I was getting ready to ask was along the same lines.

I was going to ask if the gas was coming form the fuel lines or up the impulse line and how long the impulse line is. Heavy clear tubing is recommended for impulse line so you can see what is going on in it.
The shorter the impulse line the better but of course vibration and heat have to be taken into consideration. Some where it is written that the pumps should be mounted horizontally with the impulse line entering from the bottom so any excess gas/oil form the base of the engine will drain out of the pump.

Hope this helps
[img]cid:040553614(at)17062007-270E[/img]
Noel Loveys, RPP, AME intern
Campbellton, Newfoundland,
Canada
Kitfox Mod III-A, 582, B box, Ivo IFA
Aerocet 1100s
noelloveys(at)yahoo.ca (noelloveys(at)yahoo.ca)


Do not archive



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369PL



Joined: 08 Sep 2006
Posts: 20

PostPosted: Sun Jun 17, 2007 7:28 pm    Post subject: Re: rotax pulse pump leaking weep hole Reply with quote

I also had the same problem on a 503 I used to fly on a n3pup. The pule line was to long. Their is a specification of no longer than 12". If memory serves me well.

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Mark.Napier(at)sciatl.com
Guest





PostPosted: Mon Jun 18, 2007 9:48 am    Post subject: rotax pulse pump leaking weep hole Reply with quote

Hey Tom,

The fuel can't leak out of the weep hole. It is on the other side of
the diaphragm. You went through 2 pumps so you can't have a bad one.
If the diaphragm had a hole in it the pump wouldn't operate and fuel
would run down the impulse line.

You must have a leak where one of the 3 fuel lines connects to the pump.

If you pull a low vacuum on the impulse side you would notice a slow
leak as the air slowly came in the weep hole. I would be very careful
doing that as you could damage the pump.

FWIW, on my plane the pump is installed per the instructions mounted
sideways to the firewall. Since that mounting defeats the weep hole
sump I plugged it and drilled a 2nd hold the some diameter (I think it
was .025) with a PCB drill bit at a low point down in the aluminum
casting.

Cheers,

Mark Napier

Time: 12:32:43 PM PST US
Subject: rotax pulse pump leaking weep hole
From: "Tom Jones" <nahsikhs(at)elltel.net>
The pulse pump on my 503 rotax leaks fuel out the weep hole. It is
installed according
to the kitfox manual. It is mounted high on the fire wall in a
horizontal
position with the weep hole on the bottom. I tried a new pump and
rerouting
the pulse line up over the carb flanges but it did not even slow the
amount
of fuel leaking. I am using 30R9 rubber fuel injection hose for the
pulse line.
It l;eaks about 1/2 to 1 ounce per hour of flight.

I asked this question on the Kolb list. They seem to think something is
amiss.
They don't seem to have this problem Some think the fuel pump diaphram
is leaking.
I bought a new pump but it does the same. Both pumps I have tried will
hold a vacum in the pulse chamber. I am out of ideas on how to fix
this.

--------
Tom Jones
Classic IV, Phase one
503, Warp
Ellensburg, WA


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dwight purdy



Joined: 10 Feb 2006
Posts: 85

PostPosted: Mon Jun 18, 2007 3:41 pm    Post subject: rotax pulse pump leaking weep hole Reply with quote

I think it was more like 20 in. That was too long for mine.
Dwight Purdy
model ll
marion IN.

At 08:28 PM 6/17/2007 -0700, you wrote:

Quote:


I also had the same problem on a 503 I used to fly on a n3pup. The pule
line was to long. Their is a specification of no longer than 12". If
memory serves me well.


Read this topic online here:

http://forums.matronics.com/viewtopic.php?p=119048#119048



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dwight
model II
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Tom Jones



Joined: 12 Mar 2006
Posts: 752
Location: Ellensburg, WA

PostPosted: Mon Jun 18, 2007 5:16 pm    Post subject: Re: rotax pulse pump leaking weep hole Reply with quote

My answer to those that think fuel can not enter the pulse pump vacum chamber on a two stroke is another Question.

What keeps fuel in the crankcase out of the pulse line?

The theory I have now, after responses from 2 different 503's with the same problem fixed by shortening the pulse line is:

Air pressure keeps fuel ot of the pulse line. If the line is too long the larger volume of air in the line can be compressed by the crankcase pressure, thus allowing the fuel in.

With a shorter pulse line, less air to be compressed equals higher pressure in the pulse line.

I have moved my pulse pump and shortened the pulse line from 22 to 11 inches. Now I'm waiting for the wind to calm down so I can fly and report the results.


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Tom Jones
Classic IV
503 Rotax, 72 inch Two blade Warp
Ellensburg, WA
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Tom Jones



Joined: 12 Mar 2006
Posts: 752
Location: Ellensburg, WA

PostPosted: Tue Jun 19, 2007 12:01 pm    Post subject: Re: rotax pulse pump leaking weep hole: UPDATE fixed Reply with quote

I moved the pulse pump from the fire wall to the motor mount under the carbs. I replaced the 22 inch rubber line I was using with 11 inches of clear urathane pulse line. This morning I ran the engine on the ground for about 20 minutes with several minutes at full power then flew for 2.2 hours. The weeping fuel pump is fixed. there is no sign of fuel or oil on the bottom of the pump.

I would have never figured this out without the help of the list. The old installation was according to the skystar classic four construction manual and my Rotax engine installation manual says the line should not be more than 20 inches, believe it or not.


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Tom Jones
Classic IV
503 Rotax, 72 inch Two blade Warp
Ellensburg, WA
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