Motor died. Two mysteries. Is it the snap ring on the impeller?

[ernst]

Ernst, when you shut it down check the spark again to be sure it is still the "snappy blue" spark you started with. Check it cold and keep the stuff around so you can again immediately after running.
RE the running duplicate it as much as possible by keeping the engine hatch closed except for "momentary" monitoring.

Dave Neptune

Sounds like a good idea.

RE testing the spark, how do I do that? Start the motor with one of the plugs removed, put it on the motor block and look at the spark?

Or: remove one of the spark plugs, turn on ignition, turn the motor over? I have a push-button in the motor room to switch on the starter.

And I suppose the 'snappy blue spark' will be kind of obvious, and easily distinguished from a weak non-blue spark?

Sorry, I am pretty new to this diagnostics things. As I said the A-4 ran smoothly for years and years....

tx

[thatch]

The easiest way that I know of to check for spark, is to simply use a "fifth" spark plug, laying on top of the motor. Just connect any of the four plug wires to it, and with the ignition on, crank the engine over. If there is a spark, it would indicate that the ignition system is working. If there is a spark and the engine won't run, then you either have a fuel problem, or the engine is flooded. Even though this fifth spark plug is just laying on the cylinder head, there is enough "contact" to complete the connection.
Tom

[roadnsky]

One additional step to add...

BEFORE checking for spark, smell for gas and I suggest running the blower for a couple of minutes.

I know this is a pretty basic warning but around here we'd rather be safe and state the obvious.

[ernst]

The easiest way that I know of to check for spark, is to simply use a "fifth" spark plug, laying on top of the motor. Just connect any of the four plug wires to it, and with the ignition on, crank the engine over. If there is a spark, it would indicate that the ignition system is working. If there is a spark and the engine won't run, then you either have a fuel problem, or the engine is flooded. Even though this fifth spark plug is just laying on the cylinder head, there is enough "contact" to complete the connection.
Tom

Pure genius!

One of the things where you slap your forehead and say 'why didn't I think of that?'

[ernst]

One additional step to add...

BEFORE checking for spark, smell for gas and I suggest running the blower for a couple of minutes.

I know this is a pretty basic warning but around here we'd rather be safe and state the obvious.

Duly noted.

I always run the blower and I also have a gas alarm installed in the engine compartment.

[JOHN COOKSON]

Sounds like a good idea.
Or: remove one of the spark plugs, turn on ignition, turn the motor over? I have a push-button in the motor room to switch on the starter.
tx

Don't leave the key in the on position to long when the engine is not running when you do the testing or the coil will over heat and be damaged. I don't know what the "official" guideline is. I get antsy when the key is on and the engine is't running after ~ 45 seconds.

On another subject, do you have the Moyer manual? It is a treasure trove of information on the A4. I didn't reread the thread. Maybe it has been mentioned already.

TRUE GRIT

[edwardc]

... I know how much I added, about 3 quarts. But I don't really know how much I lost in the bilge when checking the impeller. ...

Go to your local Harbor Freight and pick up one of these fluid line clamp kits. Cheap ($8), easy to use, and keeps your coolant loss to about half a cup when changing impellers.

[ernst]

Don't leave the key in the on position to long when the engine is not running when you do the testing or the coil will over heat and be damaged. I don't know what the "official" guideline is. I get antsy when the key is on and the engine is't running after ~ 45 seconds.

Thank you, will keep that in mind.

BTW, do you know if electronic ignition avoids this problem? Maybe I should think about it. But that leads us a little away from the main topic of this thread.

On another subject, do you have the Moyer manual? It is a treasure trove of information on the A4. I didn't reread the thread. Maybe it has been mentioned already.

TRUE GRIT

Has not been mentioned in this thread. But yes, I have the Moyer 'bible'.

[ernst]

Go to your local Harbor Freight and pick up one of these fluid line clamp kits. Cheap ($8), easy to use, and keeps your coolant loss to about half a cup when changing impellers.

Thank you! I had no idea such a thing exists and I will definitely pick up a set.

After I lost all the coolant in the first place, I emailed Tom Stevens (Indigo) and he suggested I use visegrips on the hoses. I did that and it worked but I am a bit concerned about damage to the hoses. These clamps looks a bit more gentle.

[Administrator]

Maybe we need to start a new category for neat toys from Harbor Freight.

Bill

[ernst]

I spent the day at the boat yesterday for data gathering. I think I
pretty much accomplished all that I had planned for.

First, I checked the coolant level. Both heat-exchanger and overflow
tank were completely full. This was expected since I only ran the
motor for maybe 10 minutes last week (see my very first posting in this
thread).

Next was the pressure test of the exhaust manifold. It was not 100%
conclusive because of 'technical difficulties.' I will spare you the
details, I had forgotten my bicycle pump at home and ended up buying
two new ones on the way, both with problems. Also, I have the
suspicion, the guy at Home Depot sold me a cap for the hose barb that
had slightly wrong threads. I ended up using A LOT of teflon tape but
I suspect there was STILL a small leak at the hose barb. So, my
contraption did not hold pressure for a long time, it went from 4psi
to 3 psi over ~15 minutes but I am 99% sure that this was due to a slow
leak either at the hose barb or in the pump itself (which I could not
disconnect since doing that caused immediate loss of pressure).

Then I did the spark test with the cold motor, using a fifth spark
plug as advised. It went well but I have absolutely no idea whether
the spark is blue and snappy or not. I tried attaching two videos, one
taken after I just turned the motor on, completely cold. The second
one was taken after two hours of running under load. Unfortunately, I
am not allowed to attach mp4 files, and the files are also too large
to upload to the site anyway. To me the sparks look pretty much
identical but I would not even know what to look for. I would love to
get experts to look at the videos but I don't know how to get this on
the forum.

Then came the main part, running the motor under load, at about
1300 RPM for a good 2 hours and measuring the temperature. After the
first 15 minutes or so, I closed the engine room door, so conditions
should be quite realistic.

Results are shown in the attached graphics. I measured at 6 locations:

1) on the hose going into the coolant pump (dark blue line in the figure)
2) on the hose from the motor block to the exhaust manifold (red)
3) on the hose from exhaust manifold to heat exchanger (yellow)
4) on the metal of the coolant filter* (green)
5) on the brass 'tee' with the gauge sensor (brown)
6) on the top of the motor block (light blue)

*The coolant filter is the one Indigo recommends to run temporarily
when installing their system. I decided to leave it in 'just in
case'. My understanding is that most commercial installations
(e.g. truck engines) have coolant filters permanently installed. BTW,
I checked the filter and it was clean as a whistle.

Observations:

a) It seems that all temps reach a stable state very quickly, within
about 10 minutes. There are some 'spikes' but I think these are
measurement errors, with one exception which is the very last data
point (more on that later).

b) Some results are surprising. The temperature at the sensor (brown
line) is pretty constantly between 130 and 140, but the gauge showed
170. I have no reason to assume the gauge is wrong. I suppose that the
outside of the brass 'tee' with the sensor is simply 30-40 degrees
cooler than the coolant inside.

c) I expected that the temperature on the coolant filter (green line)
was the same as in the drain from the exhaust manifold (yellow) since
it is the same coolant that flows in both. Instead, the filter is
about 10-20 degrees warmer. I suspect this has to do with the better
heat conductivity of the metal filter housing compared to the rubber
hoses.

d) Temp at 'Exit exhaust manifold' (yellow) is nearly consistently
lower than at 'Exit motor block' (red). This makes not sense, the
exhaust must increase the temperature. Again, my only explanation is
that there must be a difference in the hoses. Both are rubber hoses
but maybe one is thicker, or otherwise less heat conducting than the
other??

Despite these inconsistencies, overall, I think this is pretty healthy
behavior.

There was, however, some excitement at the very end of the test: A
keen eye will notice that at the very last data point (unfortunately
cut off in the graphics), all temps go up. This is because the V-belt
broke!! I knew it was suspect and it was slated for replacement but I
thought this was a good opportunity to test it 'to destruction' since
I was keeping a close eye on the motor. I actually noticed it
shredding itself during my temperature measurements until finally it
gave up the ghost. Haven't replaced it yet since doing that will be
more pleasant when the motor is cool.

I may still have a leak, though. I have the habit of putting a
disposable diaper under the motor to catch any drips of oil or
water. When I was packing up shop yesterday, I noticed that the diaper
was completely full, I would guess there must have have at least a
quart of liquid in there. I did not connect the dots up until when I
was driving home: I had replaced the diaper last week and I don't
think it rained this much (some rain water always find it way into the
bilge). So I will have to hunt for a leak. This would explain one of
the mysteries (where did the coolant go).

So where is the leak? I wonder if these very thin paper gaskets on the pumps really are enough (they are commercially made and bought at MMI). Should I coat them with anything?

Also, if there is a leak, I have no explanation why I did not notice it last
week.

And, finally, why the motor stopped, is still unclear. To me the spark
looked as good after 2 hours as at the beginning (perhaps due to my
ignorance) and the motor ran perfectly fine and round. Perhaps I
should drain the carburator and see if anything lurks in there?
Haven't done this in a year.

[Boat]

this

+1......... 10 characters

[Boat]

Maybe we need to start a new category for neat toys from Harbor Freight.

Bill

+1 10 characters

[JOHN COOKSON]

And, finally, why the motor stopped, is still unclear. To me the spark
looked as good after 2 hours as at the beginning (perhaps due to my
ignorance) and the motor ran perfectly fine and round. Perhaps I
should drain the carburator and see if anything lurks in there?
Haven't done this in a year.

Start the engine. While the engine is running shake the wiring between the key and coil +. If you have an electronic fuel pump shake the wiring between coil + and the fuel pump while the engine is running.
There may be a lose or intermittent disconnect in the wiring.
If you have an electronic fuel pump and there is wire that goes from the fuel pump to the starter let this wire loose at the starter and inspect it.
On my A4 the insulation was worn and the wire was shorting out back by the distributor where the wire turns towards the starter solenoid. Kept me guessing for many months.

TRUE GRIT

[ernst]

Oh, when I see my posting now, the graph is only available for downloading. Isn't there a way to include the graphics in the text, or at least as a little icon that makes it pop up when you click on it? All I could find on this page to include a file from a URL but it seems only URLs with https:// are allowed, not on my own file system. Help, please?

tx