Stuck valve versus plugged injector

[Viperdoc]

My AEIO 540 equipped plane had a cylinder stop working following a flight
yesterday. It ran fine during the flight, and quit on the taxi back to the
hangar. (Number 3)

It started to run rough, and a mag check showed that the cylinder was cold
on both (six probe EGT and CHT).

The plugs both look good- not shorted or oil covered or bashed apart. I
pulled the injector and at least could see light through the orifice, and it
is currently soaking overnight in solvent.

I don't have an extra valve cover gasket, so I'm a little leary about
pulling off the valve cover.

Anyway, do these symptoms sound like a plugged injector, stuck valve (only
260 tt on the engine), or something else?

Any other ideas?

My mechanic is talking stuck valve, but how do you distinguish this from
something else?

Anyway, he's coming to take a look next week, but if I can solve the problem
in the meantime it would sure be nice, since it looks like good flying
weather this weekend.

TIA

JN

[Brad Z]

Have you done a compression check?

"Viperdoc" > wrote in message
...
> My AEIO 540 equipped plane had a cylinder stop working following a flight
> yesterday. It ran fine during the flight, and quit on the taxi back to the
> hangar. (Number 3)
>
> It started to run rough, and a mag check showed that the cylinder was cold
> on both (six probe EGT and CHT).
>
> The plugs both look good- not shorted or oil covered or bashed apart. I
> pulled the injector and at least could see light through the orifice, and
it
> is currently soaking overnight in solvent.
>
> I don't have an extra valve cover gasket, so I'm a little leary about
> pulling off the valve cover.
>
> Anyway, do these symptoms sound like a plugged injector, stuck valve (only
> 260 tt on the engine), or something else?
>
> Any other ideas?
>
> My mechanic is talking stuck valve, but how do you distinguish this from
> something else?
>
> Anyway, he's coming to take a look next week, but if I can solve the
problem
> in the meantime it would sure be nice, since it looks like good flying
> weather this weekend.
>
> TIA
>
> JN
>
>

[G.R. Patterson III]

Viperdoc wrote:
>
> My mechanic is talking stuck valve, but how do you distinguish this from
> something else?

Pull the prop around six times with the mags off and the mixture at lean cutoff. If
you have a stuck valve, one of those pulls will be *very* easy.

George Patterson
This marriage is off to a shaky start. The groom just asked the band to
play "Your cheatin' heart", and the bride just requested "Don't come home
a'drinkin' with lovin' on your mind".

[Viperdoc]

Don't have one. I'm just trying to diagnose the problem with my minimal set
of tools.

[Michael]

"Viperdoc" > wrote
> It started to run rough, and a mag check showed that the cylinder was cold
> on both (six probe EGT and CHT).
>
> The plugs both look good- not shorted or oil covered or bashed apart. I
> pulled the injector and at least could see light through the orifice, and it
> is currently soaking overnight in solvent.

The odds of two clean looking plugs both being bad are low. The odds
that an injector with a visible hole was bad enough to shut down a jug
are also low. Likely something else is going on.

> I don't have an extra valve cover gasket, so I'm a little leary about
> pulling off the valve cover.

You should stock some spare rocker arm cover gaskets.

> Anyway, do these symptoms sound like a plugged injector, stuck valve (only
> 260 tt on the engine), or something else?

Could be anything. Stuck valve, plugged injector, bad plugs (I have
had both plugs go bad on one jug), bad cam lobe - anything.

> My mechanic is talking stuck valve, but how do you distinguish this from
> something else?

First off, every time I've ever had an engine problem my mechanic has
always said stuck valve. Know how many actual stuck valves I have
had? None. In any case, if you really don't want to pull the rocker
arm cover, get a flashlight and pull the prop through. You should be
able to shine the flashlight in one spark plug hole, and look through
the other (may need a mirror) to see the vlaves move as you pull the
prop through. If they open and close, it's not a stuck valve. If a
valve is stuck open, well, there you go. Do the rope trick and use
some Marvel Mystery Oil.

If it's not a stuck valve, you will have to pull the rocker arm cover.
If you damage the gasket, it can be repaired with red (high temp)
RTV, at least as a temporary measure. Make sure you have full travel
on the valves - that will eliminate the cam.

Michael

[Viperdoc]

After cleaning the injector overnight in solvent, the engine still didn't
fire on the one cylinder. My mechanic talked about the rope trick as well,
but I didn't catch the whole process.

How does it work, and is it something that can be done without a lot of
expensive or unique tools?

My mechanic (not based at my home airport) is coming down next week to work
on the plane, and he assures me he has lots of spare valve cover gaskets, so
I'm going to pull the cover off today and see if the valve actually works.
If it's not too complicated I would like to try the "rope trick".

Any recommendations on stock (cork) versus silicone valve cover gaskets?

TIA

[Michael]

"Viperdoc" > wrote
> After cleaning the injector overnight in solvent, the engine still didn't
> fire on the one cylinder. My mechanic talked about the rope trick as well,
> but I didn't catch the whole process.

Take a piece of rope, 1/4" diameter or so, very long, and stuff the
cylinder with it through the plug hole. Then move the prop carefully.
The rope will compress, push on the valve, unstick the valve, and get
it to close. Make sure you do this during the cycle where the exhaust
valve is supposed to be closing!

Do not do this until you are sure that this is the problem. Once you
pull the rocker arm cover gasket, it will be obvious - you will have a
valve that won't close, and you will be able to move the rocker arm
without any force.

It would be best if you could get someone to show you how it's done -
it's common enough, and lots of us who are not A&P's know how.

> Any recommendations on stock (cork) versus silicone valve cover gaskets?

Cork gaskets are cheap, and generally you get them wil cylinder kits
and such. All of them leak eventually. If you're a neat freak, go
for silicone - they last forever and don't leak. If you're like me
and don't consider a couple drops of oil a big deal, well, cork is a
lot cheaper.

Michael