Kingsley,
I have a 914 Engined XS Trigear.
A year or so ago, I had a rough running engine, had the Rotax Engineer up
just before the problem started to service it, and then the trouble starte
d.
When I did the engine checks, all OK, even tried doing them with the prop
fully coarse, still OK. Start up the runway, push through the gate into
full turbo, then the engine popped and banged and misfired! Float bowls w
ere
checked, filters changed, fuel flow checked, jets checked, airbox rubbers
checked, turbo wastegate checked, just about everything you could think of
.
The problem turned out to be the carb slides. All they needed was a very
light polish and some lubrication and hey presto, a fully serviceable
engine! They had not been running level, despite the cables being spot-on
and
so the carbs were massively out of balance on full throttle. After the
lubrication, they both operated perfectly and balanced without adjustment.
As your Engine had not been run for a long time, suggest you have a look
and lubricate the slides.
best regards
Trev
G-LINN
In a message dated 13/08/2011 12:17:50 GMT Daylight Time,
kingsnjan@westnet.com.au writes:
--> Europa-List message posted by: "Kingsley Hurst"
<kingsnjan@westnet.com.au>
Fellow Listers,
Almost 3 weeks ago, Tony Renshaw posted the following plea on my behalf.
My
apologies for not repsonding before this but circumstances have prevented
me
---From doing so.
I would sincerely like to thank those who came forward with suggestions
which are now repoduced below together with my responses / comments. The
long and the short of it is that given the remoteness of our landing
aerodrome, the lack of testing equipment and time constraints, we left the
aircraft thankfully in a hangar and intend returning soon to retrieve it
with my trailer.
Tony's posting . . . .
> I've got a mate, who we all know, Kingsley, trying to fly a 914 a long
> distance downunder that is giving him angst. Its running rough, real
> rough. It seems that at boost power it just simply cuts out! Also, in
> cruise when going to climb power it has begun to run really rough. He is
a
> long way from home trying to limp it home, so any suggestions would be
> greatly appreciated. To elaborate, he has flown it 2 hours on AVGAS with
> no obvious problem until going to climb power when it ran so rough they
> had to pull the power back and land ASAP, luckily with an aerodrome
> closeby. Now, it runs rough on the ground too.not sure of what
power
> settings but I recall they can't get boost happening. The local Rotax
> agent says that AVGAS with lead can wreck a set of plugs in no time, so,
> they have a new set of plugs about to be installed. Fuel will be drained
> and high octane super unleaded mogas will be used instead. The system
will
> be drained. So, I'm wondering if ASAP those in the know can beam
downunder
> the "good goss" that can help Kingsley get this bird home.
BRIAN DAVIS . . . .
> Sorry to hear of Kingsley's troubles. It is difficult to diagnose such
a
> problem remotely but there are a couple of obvious things to check. If
> the engine runs smoothly at lower power settings and cuts out at higher
> power settings I would strongly suspect a fuel flow restriction as first
> guess. I suggest he does a fuel flow check to see if he is getting
enough
> flow. Next check that there are no air leaks caused by carb mount
> failure/pipes adrift/blocked. Check both carbs are opening together/ no
> problems with throttle cables.
It could be ignition and changing the plugs and fuel at least eliminates
some things but it is unlikely that a short period on Avgas would cause
plug
failure.
Response . . .
We are convinced the problem is fuel or rather lack of however, we did
fuel
flow tests the result of which was 10 litres over a 4 minute period on
each
of the two fuel pumps. This equates to 150 LPH which is more than enough
for the 914. Inspection of the gascolator and another filter revealed
they
were as clean as a whistle.
There were no visible signs of any fuel leaks around the float bowls, carb
mounts all appeared normal as did everything else we checked by looking
and
feeling. Both carbs opened very smoothly and in unison. Both throttle
valves simultaneously contact idle stops and in turn, the full throttle
stops. There was absolutely no sign of any sticking throttle cables.
We replaced the fuel and fitted new spark plugs only because we were
advised
to do so by the Rotax agent. We were not convinced it would have any
effect
(and it didn't) but we did as advised because we thought we had nothing to
lose. We now have a spare set of spark plugs as a result of the exercise.
JIM BROWN . . . . .
> Try this. turn off the turbo with the Isolation switch....Do a run up,
if
> you get full power, and no missing, without the turbo, then leave the
> turbo out of the circuit and fly home....
The fuel regulator on top of the airbox is bad. As the engine RPM is
going
to full power, at about 4400 RPM the missing starts.,the fuel regulator on
top of the airbox, is supposed to shut off the return fuel, so that all
fuel
is avaiable for the turbo. In other words the engine is starving for fuel
under boost. The engine will run just fine as a non-turbo.....
Response . . . . .
Turning the turbo isolation switch off was one thing we hadn't thought to
try Jim so when Tony relayed your message, I had high hopes it would be
the
answer to a maiden's prayer. Alas, it had no effect so you can imagine my
disappointment. I am however convinced the problem IS the fuel pressure
regulator Jim but not having the equipment to do any tests and with very
limited tools available, we were unable to check it. The fact that the
regulator is common to both carbs indicates to me a logical reason why the
engine completely cut like it did on 3 occasions. On one occasion when
the
throttle was left open, the engine all but stopped before it fired up
again.
This aircraft had not been flown for 2 years and I suspect the diaphragm
may
have dried out and become porous or some dried out fuel residue may be in
some orifice or something else just as sinister. I may be talking crap
here
because I have not yet seen the inside of a 914 regulator.
Now that I have read your full posting, with hindsight and as a result of
the steep learning curve I have been on regarding the 914, maybe if I had
clamped off the fuel return line somewhat, we may have at least seen some
change in the running to confirm we might be on the right track.
KEVIN KLINEFELTER . . . .
> You can check the operation of the turbo wastegate on the ground. Ob
serve
> the wastegate arm move through it's test cycle when the master is turned
> on, to see if it is sticking.
Sounds like carburators to me. He can inspect and clean the float bowls
without removing the carbs from the engine ( 19 mm bolt on the bottom of
the
bowls, torque to 5.5nm). Also make sure that the carbs are balanced
Response . . . .
Wastegate works perfectly on turn on thanks Kevin. Have repeatedly
observed
it cycle as you suggested. Because of the sophiscated fuel drain trays
under the carbs, we were unable to remove the float bowls and didn't have
sufficient tools to go any further. However, a few weeks before we
picked
up the aircraft, a yearly inspection was carried out during which the
carbs
were both removed, checked and some gaskets replaced. The carbs were also
balanced. The complete cutting of the engine we experienced leads me to
believe it would not be the carbs because I cannot see two carbs failing
simultaneously except for lack of fuel as aforementioned in my response
to
Jim.
WILLIAM DANIELL . . . .
> I use 100% AVGAS and in my experience no it doesn't. Plugs last 50
hours
> no problem. I have never had a set of plugs foul up in nearly 7 years
-
> I admit I change them every 25 hours.
I have this sort of issue after an overhaul and it had to do with two
things. Part of the problem was one of the tubes from the airbox the carb
had come loose and unbalanced the carbs
Secondly the mating between the turbo and the engine was "out" - which
meant
that the turbo was providing too much or too little boost relative to the
power setting. We tested the system by making the wastegate "manual" wit
h
a vernier cable.
Response . . . .
I agree with you about the AVGAS William. The plugs in this engine had
only
done 3.5 hrs at the time so it would need to be special Avgas to stuff
them
in that amount of time. On inspection, the plugs showed signs of running
a
bit lean if anything which would be consistent with the rough running at
higher power settings I would think. There was no sign of lead in them
and
during the 4 hour return trip by car to purchase new plugs, we had the
removed plugs tested on a plug tester. All were Ok. I have not yet had
the
chance to check the other items you mention William so am unable to
comment
on those yet but they will be checked at a later stage thanks.
PAUL McALLISTER . . . .
> If Kingsley's airplane only has a couple of hours on it then I'd be
> looking at the fuel filters. I pulled an unbelievable amount of crap
out
> of the filters for the first 50 hours and I was very careful (or so I
> thought) to make sure that fuel system was clean before my first flight.
Response . . . . .
This aircraft has done 330 hours Paul but nothing for 2 years. As
mentioned
earlier, we did check the filters to no avail and a fuel flow check proved
satisfactory. When I finally get to flying my own aircraft Paul, rest
assured your suggestion will be strictly followed.
Thank you again one and all for your contributions. Many heads are
certainly better than a couple as bereft of 914 knowledge as ours were at
the time. I will advise the outcome in due course.
Best regards
Kingsley
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