Mandatory SB565 Lycoming fuel pump

I had the pleasure of loosing power on the left engine on my
Aztec at about 30'AGL after takeoff. Because of poor checklist
performace on my part, I had failed to turn on the electical AUX
pumps. Luckily hitting the AUX pump restored power within a few
seconds giving me the option of climbing to altitude to troubleshoot.
As I climbed, above pattern altitude, I monitored the fuel pressure
and turned the AUX pump off to see what happened, and sure enough
the fuel pressure began to fall. I turned the AUX pump back on to keep
fan turning and decided that I had a failed mechanical engine driven pump.

Since there were no repair facilities at the departure airport,
I climbed to cruise altitude and headed for the closest airport
with a mechanic. Once I was leveled off, with cruise power
and mixture set, I again monitored the fuel pressure and turned
off the AUX pump to confirm the mechical pump failure. To my
supprise, the fuel pressure remained up and the engine ran great.
I even increased the throttle and the mixture and everything
continued to work great. Switched between inboard and outboard
fuel tanks on the left side. No problem. Did the problem fix itself?

Decision time again. Should I land at the closest airport with a mechanic
and investigate or press on? I knew that a number of airports lay
along my route of flight and the weather was CAVU, so I had plenty
of options. I decided to continue along my route while carefully
monitoring the left engine's fuel pressure and then get my mechanic
to fix the problem if I made it all the way home, about 2.5 hours of
flying time. (This is one place where having a second engine is nice).

The left engine ran great all the way home with never another glitch and
never a dip in the fuel pressure. However, when I upcapped the left
outboard
tank to refuel, I was supprised to hear a sucking sound of air rushing into
the
tank. Ah ha! A plugged fuel vent.

Sure enough, my mechanic and I found the left outboard tuel tank
vent tubing was almost completely plugged, way up inside, about halfway
between the vent port and the tank. The handy work of a crafty bug with
a flare for sturdy construction work. We cleaned that out, checked the
other
three tanks' vents for the same problem. This is a good argument for
capping
the fuel vent ports when the airplane is parked, just like we cap the pitot
tube.

A full power static run up was done and everything looked good. The theory
was that under full takeoff power, and with a full fuel tank, the vaccum in
the tank
was too great for the engine driven pump to keep the engine feed with fuel,
and that
the extra boost of the AUX pump was enough to overcome this and keep things
working. Once I got to altitude, the engine driven pump alone was able to
keep up
with the reduced fuel flow demands.

Problem solved, right? Wrong! On the very next takeoff, the same probem
happened with loss of left engine fuel pressure. With the mechanic on board
monitoring the fuel pressure, we turned the AUX pump off as we began our
climb as a test. Sure enough, the fuel pressure started dropping. The AUX
was turned back on to restore fuel pressure and to keep the engine running.

The mechanic dicussed the problem with a fuel injection system overhaul
shop and the suggestion was to repace the mechanical fuel pump. We did
and that solved the problem. Out of curiousity, I disassembled the the old
pump to see if I could see a problem, and it was not hard to find. The
rubber
diaphram was split about 3/4s of the way around at one of the creases where
it was designed to flex.

I'm not sure if the plugged vent line caused the diaphram to split, or if
the
diaphram just split from old age / wear and the pump was not able to
overcome
the vaccum caused by the plugged vent. However, after the pump was damaged
and the vent was clear (the second takeoff) the pump was not able to supply
the engine with the necessary fuel flow.

The point is, failure of the mechanical engine driven pump can be
intermittent and
only appear then the load on the pump is greatest (takeoff) even though the
pump
has a major defect. Therefore, I'd not take any risks. If Lycoming is
concerned
about their pumps, I would be too. If the pumps on my Lycoming IO-540s on
the
Aztec fall under this service bulletin, I will replace them.



"BTIZ" wrote in message
news:iU5_d.72049$Tt.31211@fed1read05...

And if you need an engine driven pump then you probably already have a
backup electrical pump. Would there really be any need to replace the
mechanical one before it wears out?


Are people actually flying with this logic?

Key words here are "need" engine driven pump and "backup" electrical.

Is it a matter of the pump failure that could cause other problems besides
fuel pressure, like lack of fuel flow.. do you know why the SB was
suggested?

Like another poster said, it's free.. why NOT do it.

BT

Paul kgyy wrote:

I received a notice in the mail. It says,

"If your Lycoming engine has a diaphragm-type fuel pump with Lycoming
P/N LW-15473 installed, and has a date code of 3201, the pump must be
replaced PRIOR TO NEXT FLIGHT."

The defective pumps were shipped from Lycoming between 10/1/01 and
2/2/04.

It affects a wide range of engines from 320 to 540, IO, O, AIO, TO



I got that last year and check. I passed! (O-360)

Ross

"nobody" writes:

I had the pleasure of loosing power on the left engine on my
Aztec at about 30'AGL after takeoff. [...]
The left engine ran great all the way home with never another glitch
and never a dip in the fuel pressure. However, when I upcapped the
left outboard tank to refuel, I was supprised to hear a sucking
sound of air rushing into the tank. Ah ha! A plugged fuel vent.
[...]

Did it occur to you to switch fuel selectors between inboard/outboard
or try the crossfeed, back during the early iffy-pumping phase of the
flight?

- FChE

"nobody" writes:

[...] Sure enough, my mechanic and I found the left outboard tuel
tank vent tubing was almost completely plugged, way up inside, about
halfway between the vent port and the tank. [...] This is a good
argument for capping the fuel vent ports when the airplane is
parked, just like we cap the pitot tube. [...]

How would you do that with an Aztec? Each fuel tank's vents open on
the underside of wing, one exiting in a big hole in this ceramic-like
block, and a second little vent tube to drain liquids from the big
one. Both point mostly down (and there are eight of them total).

- FChE

Michael wrote:
snip
In other words - Lycoming's offer is not particularly generous
(certainly not up to what you would expect for a recall in the
automotive world) and this will probably still cost you.


OK, I'll agree that maybe Lyc.'s offer of 1.5 hrs won't cover the
labor on some planes. It will on mine (BTDT). As compared to
automotive recalls, you're right, but in my experience, the majority of
aircraft S.B.s that I see don't offer any compensation from the
manufacturer (unless the part or plane is still under warranty). In
that respect, I'm pleasantly surprised.

John Galban=====N4BQ (PA28-180)

Yes, after I got some altitude, I did switch tanks to see if the problem
was associated with a particular tank, but the fuel pressure was fine on
both the inboard and outboard tank.

The big vents can be sealed with a small cork or rubber stopper with a
long red "REMOVE BEFORE FLIGHT" ribbon attached. Just push
them into the hole. I've not tried to seal the small vent lines.

The big vent opening is where the bug did his job in my case. That
tube leads up to a cylinder where the small tube is attached. In our
case, the blockage was in the large tube, althought you're correct in
that a tiny bug could also crawl up the tiny vent tube and get into the
vent system.


"Frank Ch. Eigler" wrote in message
...

"nobody" writes:

[...] Sure enough, my mechanic and I found the left outboard tuel
tank vent tubing was almost completely plugged, way up inside, about
halfway between the vent port and the tank. [...] This is a good
argument for capping the fuel vent ports when the airplane is
parked, just like we cap the pitot tube. [...]

How would you do that with an Aztec? Each fuel tank's vents open on
the underside of wing, one exiting in a big hole in this ceramic-like
block, and a second little vent tube to drain liquids from the big
one. Both point mostly down (and there are eight of them total).

- FChE

Kyle Boatright wrote:


Yep. A mandatory service bulletin is designed to do two things...

1) Get the word out that there is or may be a problem.

2) Reduce Lycoming's liability.


If you're a commercial operator it has more meaning.

Ben Jackson wrote:
On 2005-03-16, Michael wrote:

you are not grounded and
you are not required to replace anything.


And if you need an engine driven pump then you probably already have a
backup electrical pump. Would there really be any need to replace the
mechanical one before it wears out?

Do you avoid replacing the tires on your car until they fail because
you have a spare?

Ron Natalie wrote:
And if you need an engine driven pump then you probably already
have a
backup electrical pump. Would there really be any need to replace
the
mechanical one before it wears out?

Do you avoid replacing the tires on your car until they fail because
you have a spare?

Hardly a fair comparison. Tires are wear items; you replace them when
the tread is worn down to a certain level.

The fair comparison is your brake power pump. If it fails, you have
very limited backup. How often do you replace that?

Michael