Need help with a problem in our PA28-140

[Prime]

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 prime>crank>fire>die. 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 prime>crank>fire>die 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 prime>crank>fire>die 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

[Mike Spera]

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 prime>crank>fire>die. 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 prime>crank>fire>die 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 prime>crank>fire>die 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

[Prime]

Mike, thanks for the feedback. One comment, at previous times the boost
pump clicking would usually stop once pressure was built up in the
lines. When this problem occurs the clicking never stops. I don't think
that's normal, since it doesn't occur when we get a "normal start"?

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 prime>crank>fire>die. 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 prime>crank>fire>die 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 prime>crank>fire>die 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
>

[Prime]

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 prime>crank>fire>die. 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 prime>crank>fire>die 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 prime>crank>fire>die 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
>

[RST Engineering]

Prime, no, just the opposite. The water that leaked into the old scat hose
drained out through the holes in the old hose. The new hose doesn't leak,
therefore the water stays inside the hose to be sucked up into the engine.

PLEASE learn to snip. We really don't need to relive the whole thread. All
it does is waste bandwidth.

Jim



"Prime" > wrote in message
5.20...
> 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?

[Dave[_3_]]

Hey Prime!

Are a member of the Cherokee group?

http://www.piperowner.com/

Probs like yours are discussed regularily there...

...A must for a Cherokee driver....

Dave

On 15 Feb 2007 00:50:16 GMT, 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 prime>crank>fire>die. 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 prime>crank>fire>die 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 prime>crank>fire>die 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

[Mike Spera]

Prime wrote:
> 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?
>


As Jim said, the opposite is likely true. The old tubing was probably
beat up and perforated in several spots, thus letting the water OUT that
was leaking in from the airbox.

If you remove the nose cowling, I can almost guaranty some cracks in the
airbox. Hold the cowling upright in its normal position, spray water at
the front from a high up angle (mimicking rain), and look to see where
it runs. I'll bet it goes into cracks and out the round tube that
connects to the scat tube. All it takes is an ounce or two.

As I said, I had the exact same problem after replacing my main
induction scat tube. A little hole punched in the bottom cured it. Until
then, start it up with the carb heat valve opened half-way to prevent
the water from being sucked in on startup.

Good Luck,
Mike

[Mike Spera]

Prime wrote:

> Mike, thanks for the feedback. One comment, at previous times the boost
> pump clicking would usually stop once pressure was built up in the
> lines. When this problem occurs the clicking never stops. I don't think
> that's normal, since it doesn't occur when we get a "normal start"?
>

Although I believe this is unrelated to your problem, it does not sound
normal in the opposite way you are describing. I believe they should
never stop running.

It has been many years since I dismantled an electric fuel pump, but I
believe these pumps have a spring loaded internal bypass valve that
maintains pressure. They are made to run constantly. If they stop, that
indicates a problem.

Wrenches?

Good luck,
Mike

[Ray Andraka]

Mike Spera wrote:

> Prime wrote:
>
>> Mike, thanks for the feedback. One comment, at previous times the
>> boost pump clicking would usually stop once pressure was built up in
>> the lines. When this problem occurs the clicking never stops. I don't
>> think that's normal, since it doesn't occur when we get a "normal start"?
>>
>
> Although I believe this is unrelated to your problem, it does not sound
> normal in the opposite way you are describing. I believe they should
> never stop running.
>
> It has been many years since I dismantled an electric fuel pump, but I
> believe these pumps have a spring loaded internal bypass valve that
> maintains pressure. They are made to run constantly. If they stop, that
> indicates a problem.
>
> Wrenches?
>
> Good luck,
> Mike

On mine, it continues to run but it gets a lot quieter once the fuel
pressure builds up.

Does your pressure build to the normal level when this happens? Could
be that the fuel pump needs new seals.

[Prime]

That's what I meant and understood, thanks.

As far as bandwidth, I just figured keeping the context was a good idea.
Given broadband speeds, that amount of text is negligible on bandwidth. Now
if somebody is still on a dial up modem (heaven forbid) then you're
correct.

"RST Engineering" > wrote in
:

> Prime, no, just the opposite. The water that leaked into the old scat
> hose drained out through the holes in the old hose. The new hose
> doesn't leak, therefore the water stays inside the hose to be sucked
> up into the engine.
>
> PLEASE learn to snip. We really don't need to relive the whole
> thread. All it does is waste bandwidth.
>
> Jim
>