Oh and Mike, thanks for the water issue suggestions. Your explanation
would cover the symptoms we are seeing, I hadn't thought of that. We
will check it out. I do believe we replaced the tubing at that annual.
Are you suggesting that the old tubing may have leaked just enough to
trap the water, where previously it would have drained? What would be
different with new scat tubing?

Mike Spera wrote in
k.net:

Let's take them in order:

* the boost pump clicking over is normal. This is not a sign that it
"cannot hold pressure". The pump rebuild was likely not necessary.
* The fuel selector valve needs new seals. I would suggest it gets
done now. Fuel leakage is rarely a good thing.
* There is no water in the FUEL system.

Now the big one. Your problem is that rain water is collecting in the
scat tubing that goes from the air filter to the carb. Upon startup,
the high vacuum when the engine revs is sucking gas in and flooding
the plugs rendering them inoperative.

I had the exact same problem AFTER replacing my ragged scat tubing
with a new piece. I suspect yours was also replaced at the annual when
this first started happening. Check your log books.

Rainwater can get in from a number of places, but the most common
appears to be from cracks in the fiberglass nose cowling on the
corners of the air filter retaining box and where the round piece
intersects the back of the box. It is dripping down the inside of the
cowling, running over and into the cracks, and collecting in the scat
tube. Get some good cowl plugs to help keep rainwater out. Also, you
can fiberglass the cracks shut or use silicone sealant on them.

Another thing that helps is to punch a tiny hole in the tube at the
lowest point in the scat tube. Also, you can open the carb heat
control half way when starting up. Then, SLOWLY return it to "off"
after the engine starts and is running at fairly high RPMs (like in
the runup).

When it is cold, the water that is ingested can freeze the carb throat
in addition to coating the plugs. You can add carb heat to try to
clear it.

This problem will drive you nuts when the temps hover around freezing.
The water freezes in the tube and melts as the engine warms up. The
ice ball can break loose and choke off the carb (guess how I know).
Once the engine dies out, hop out of the plane to watch a stream of
water running from under the cowling. In southern CA your problem will
be limited to killing the engine and coating the plugs with water.

Good Luck,
Mike

Prime wrote:
We have a really weird one and I'd like some help in the diagnosis.

We're in Southern California and have a 1974 Cherokee Cruiser with
the O-320E3D.

Background:

About a year ago we had our annual. During the annual our mechanic
took apart the gascolator and checked/cleaned the area.

We flew the plane home from the "annual" field to the "home" field
without problems.

In the next flight or two, we had a situation that would repeat
itself a number of times in the last year: During an attempted cold
start, we would primecrankfiredie. The primer appeared to burn off
and then nothing would get the plane started.

I noticed that when trying to start the plane I heard the aux fuel
pump continue ticking as if pressure couldn't be maintained in the
system. Additionally, there was some gas inside the plane near the
fuel tank valve. Our on-field mechanic checked the plane and removed
and reassembled the aux fuel pump, cleaned out the primer lines, and
rebuilt the mags which probably needed it anyway.

One item was that this starting problem happened after a rain.

During the summer, we had an uncharacteristic rain. My partner tried
to fly and the same primecrankfiredie sequence occurred. He pulled
the plugs and found what appeared to be water in them. He cleaned
them and put them back in, and the engine fired up and ran normally.

Forward all the way to a few days ago. The plane had been down for a
nose strut rebuild, and my partner flew the plane afterwards. The
next day we had a very small amount of rain. I went out the next day
to fly, having been grounded for the strut repair for a few weeks.
Since it had rained and I suspected rain might have something to do
with the starting problem, I made sure and sumped both tanks and the
gascolator. No trace of water.

The same sequence of primecrankfiredie occurred with me. After
this happened I then re-sumped everything and still found no water. I
did notice that once I couldn't start the plane, the aux fuel pump
kept ticking as if there was a pressure leak in the system. I looked
under the engine and saw some fresh fuel under the carburetor on the
nosewheel pant. Since I didn't have any tools with me to pull the
plugs, I gave up for the day.

A couple of days later my partner went to the plane, pullled the
plugs, and found water. He dried the plugs and the plane started
right up.

Observations:

- This has only occurred after it has rained
- When it occurs it seems that the fuel pump cannot maintain pressure
- We've seen some fuel leakage but no consistency here
- We've had it occur even though we don't find obvious water in the
system
- The two times we've pulled plugs they appeared to have water on
them - When it hasn't rained the full starting sequence has been
normal and we've seen no fuel leakage

Based upon this reocurring problem, we've put some tools in the plane
so that we can always pull the plugs. Yet I don't really trust flying
the plane a long way or especially if precipitation is forecast.

Anybody have any ideas on what could be happening here?

T. Long