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Christen Fuel Pump troubleshooting



 
 
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  #1  
Old August 11th 03, 10:05 PM
ShawnD2112
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Default Christen Fuel Pump troubleshooting

Hello, folks. I'm fishing to see if anyone else here's had the same problem
I'm having.

I've got a Pitts S-1D with a Christen wobble fuel pump. The action on it
has gotten so stiff when priming that I fear it's close to locking up. It
still primes fine and the fuel pressure's good when the engine's running,
it's just the hand actuated side of it that's got me concerned.

Anyone else ever have this problem? Can these things be lubricated? Any
info greatly appreciated.

Cheers,
Shawn
Pitts S-1D G-BKVP


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  #2  
Old August 12th 03, 01:06 AM
Bushy
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Default

Not knowing this pump, but having heaps of experience on old car ones, check
the flow with the output line disconnected to see if it does flow correctly
each stroke.

Valves and passages can gum up with deposits and restrict flow, alloy
housings can corrode causing similar results. My old 1964 Series 2A
Landrover hand pump will not prime the lines if the carby bowl is full as
the needle valve woon't open and the output line becomes pressurised.
Relieving the pressure by loosening the inline fuel filter lets the air out
and the line (and pump) primes happily then.

The pump on another old ex-army truck had a mesh screen that was full of
junk that had to be scraped out with tools. This truck had only 30,000 miles
on the clock, but the old fuel had still caused it to corrode and gunk up.

How much fuel, and how many years of crap has been through your tank and
lines? How hard do you shake up your tanks when flying a hammerhead? If
there is a flaky rust spot on the side of the tank, it's sure to come loose
when you least expect it, probably in straight and level flight.

If the pump can be taken apart, I'd tend to have a look, even if only to
feel comfortable with the operation that your life may depend on.

Hope this helps,
Peter


  #3  
Old August 12th 03, 06:09 AM
ShawnD2112
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Default

Thanks for the tips, Bushy. That's the funny thing in that the fuel
pressure is fine and the engine runs perfectly well. It's just the handle
is too stiff as though it needs to be oiled.
Shawn
"Bushy" wrote in message
...
Not knowing this pump, but having heaps of experience on old car ones,

check
the flow with the output line disconnected to see if it does flow

correctly
each stroke.

Valves and passages can gum up with deposits and restrict flow, alloy
housings can corrode causing similar results. My old 1964 Series 2A
Landrover hand pump will not prime the lines if the carby bowl is full as
the needle valve woon't open and the output line becomes pressurised.
Relieving the pressure by loosening the inline fuel filter lets the air

out
and the line (and pump) primes happily then.

The pump on another old ex-army truck had a mesh screen that was full of
junk that had to be scraped out with tools. This truck had only 30,000

miles
on the clock, but the old fuel had still caused it to corrode and gunk up.

How much fuel, and how many years of crap has been through your tank and
lines? How hard do you shake up your tanks when flying a hammerhead? If
there is a flaky rust spot on the side of the tank, it's sure to come

loose
when you least expect it, probably in straight and level flight.

If the pump can be taken apart, I'd tend to have a look, even if only to
feel comfortable with the operation that your life may depend on.

Hope this helps,
Peter




  #4  
Old August 16th 03, 03:24 PM
Bushy
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Posts: n/a
Default

Where does the handle hinge at? If the hinge pin or housing is worn, it may
cause stiffness like an old door hinge.

Might be as simple as replacing a pin, or the diaphragm may have gone hard?

Hope this helps,
Peter


  #5  
Old August 17th 03, 12:08 PM
ShawnD2112
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IT's attached to a pin that goes all the way through the pump and is held in
place by the houseing on both ends. It doesn't appear to be worn and the
airplane only has about 80 or so hours on it, so wear of the pump or
hardening of the diaphragm seems pretty unlikely (I'm hoping). Someone else
suggested adjusting the pressure-control screw to see if that makes any
difference.

Thanks for the tip, though. I may end up investigating those conditions as
well.

Shawn
"Bushy" wrote in message
...
Where does the handle hinge at? If the hinge pin or housing is worn, it

may
cause stiffness like an old door hinge.

Might be as simple as replacing a pin, or the diaphragm may have gone

hard?

Hope this helps,
Peter




 




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