"PaulD" wrote in message
oups.com...
I did some more testing today and got more ambigous results. First, I
had the battery charged up again (local parts store does it for free).
Tested the battery under load one time. Got 10.5 volts. Then I tested
for voltage drop at the starter. This time I got 9.5 volts, a one volt
drop, slightly better than last time
I also tested both sides of the circuit per Ether Jone's suggestion.
On the negative side I got a reading of .25 volts. On the positive
side, I got a reading of about .5 volts.
I'll have a little time off my day job tommorrow to tinker so I'll
take a closer look at the cables and connections and maybe try
replacing one. I thinking at this point, though, the cranking problem
looks like it may be at the starter.
Also, the local parts store will lend me a compression gauge. I
took a look at the CD-ROM manual. It suggested comparing the
compression between the two cylinders and looking for a significant
difference in readings between the two.. Is this the compression test
that you would recommend?

Ether Jones wrote:
That is a good way to test the compression. However, a compression test is
not of any use to diagnose a slow cranking problem. Abnormal compression is
very rarely too high and if the compression is too low the cranking speed
would be greater. It is possible for excessive fuel or oil in the cylinders
to cause slow cranking but it should blow out if you remove the plugs and
crank the engine.

I would suggest that you remove the plugs and check that the engine spins
over easily. If it does that but turns over too slowly with the plugs in and
9.5 volts across the starter, the starter is very likely not performing
properly.

Don Young
PaulD wrote:

I'll follow up tommorrow or the next. I noted the voltage drop the
first time I had the engine cranked so I am fairly certain the battery
was still at full charge. As I continued, I did notice the battery
power was dropping so I put a jump between a car battery and the lawn
mower. Still got a low voltage reading at the starter motor. I'll make
sure the battery is fully charged again before proceeding further with
your suggestions.

I ran all the tests with the plugs installed.

The starter motor has a wire going from it that is attached at the
other end to some type of terminal. Is this the s olenoid?

It is the relay. When you turn the key, the electrical switch in the
key activates the relay, which completes the circuit to provide power
to the starter motor. The relay is designed to handle the large
current; the key switch is not.

If you test the ground side of the circuit as described in the prior
post, and you get a zero reading, and then you test the positive side
and get a non-zero reading, then you can start working your voltmeter
lead backwards from the starter motor terminal until you cease to get a
non-zero reading (with the other voltmeter lead always on the battery
positive terminal post). That will isolate where the problem is. It
could be a bad relay, or a loose or corroded connection, or a wire with
several strands broken internally.

Again, this only addresses the weak cranking. It doesn't address why
the engine stalled. The stalled engine could be due to spark, fuel, or
compression (bad plugs, bad ignition system, clogged fuel filter,
clogged air filter, carburetor problem, bad gasoline, valves, etc).
Once you get the engine cranking properly, you can troubleshoot that.


I followed
the cable from the starter motor to its other end and tested for a
voltage drop there. I thought this might indicate whether there is a
problem in the cable that leads to the starter motor.

I didn't noticed any problems with slow cranking prior to the stalling
incident, except as indicated earlier about the intermittent behavior.
In some ways it is hard to know whether there was any gradual
deterioation because usually the engine fires up quickly so the starter
does not crank that long. After the stalling incident, however, it
was noticeably very weak (i.e barely cranking).


Ether Jones wrote:
PaulD wrote:

Ok, here is the update. I measured the voltage at the starter
engine
terminal.

By the way, it's a starter motor, not a starter engine.

I did it a bunch of times. I measured sometimes slightly
below 9 volts, sometimes slightly above. There was definitely a
voltage drop. Was the drop large enough to be significant?

You ran this test with the plugs installed, is that right? It's
important. If you got 9 volts at the starter with the plugs removed,
and you got 10 volts at the battery with the plugs installed, then it
seems likely that you have a problem of some sort with the cabling
between the battery and starter motor.

If the 9 volt reading was with the plugs installed, it's less
definitive but still suggests a cable problem. I would have expected
the reading to be closer to the same reading you said you got at the
battery terminals: slightly over 10 volts. But perhaps you've worn
the battery down a bit with all this cranking, and the voltage at the
battery is now only 9 volts. It would be good to check it quickly
again to make sure it's still 10 volts there. It's the difference
between the two readings that's significant.

Assuming the two readings are indeed different, you can try to locate
the cable problem. First test the ground half of the
battery-to-starter cabling: connect one voltmeter lead to the
negative
battery post, and the other lead to engine ground (cooling fins).
Make sure the plugs are installed. Make sure the voltmeter leads
have
a clean contact. Crank the engine and note the voltmeter reading.
It
should be zero or nearly so. If you get a non-zero reading, it
indicates abnormal resistance in the ground side of the connection.
Make sure your voltmeter leads have good contact. You may get an
erroneous "zero" reading if your leads are not firmly in contact with
good clean metal.

Second, test the positive half of the battery-to-starter cabling:
connect one voltmeter lead to the positive battery post, and the
other
lead to the starter motor positive terminal. Make sure the plugs are
installed. Make sure the voltmeter leads have a clean contact.
Crank
the engine and note the voltmeter reading. It should be zero or
nearly
so. If you get a non-zero reading, it indicates abnormal resistance
in
the positive side of the connection. Make sure your voltmeter leads
have good contact. You may get an erroneous "zero" reading if your
leads are not firmly in contact with good clean metal.



I also noticed that every once in a while I got a voltage spike at
about 14 volts for a very brief instance. I am not sure whether
the
spike was just a multi-meter error or whether it has some
significance.
I also tested the voltage drop where the starter cable is attached
to
the solenoid (?). I got similar readings there.

I have the service manual right here for the model 422707 Briggs
engine. The starter motor only has one terminal. I'm not sure what
you're referring to.

I did your suggestion regarding compression. I got alternating
puffs
and suction from both cylinders. Its hard to tell whether they
were
both similar. Seemed like they were.

This is one of those tests where if you did NOT feel alternating
compression and suction it would definitely indicate a problem; but
if
you DO get alternating compression and suction the test is not
definitive (there could still be a problem - only by using a
compression gauge could you be sure). Let's assume for the time
being
that the valves are OK, although that's not a sure bet.


My son said that the engine slowly faded before stalling out.

That's not what I was asking. I was asking about the starter motor
cranking. Were you noticing increasingly "weak" starter motor
cranking
in the days (or weeks) leading up to the stalling incident, or did
the
weak cranking manifest itself suddenly right after the stalling
incident?


Finally, two other things I observed. First, I did try to get
multiple
readings. As I did so, I noticed that the starter engine casing
did
get hot to touch. I did not have my helper crank for more than a
few
seconds at a time. Is this something one would expect when
cranking
the starter a number of times or is it an indication of a problem.

It's probably normal but I wouldn't swear by it. Depends on how many
times "a number of times" is, and how long each time lasted. Sounds
like the battery was getting quite a workout. In view of this, it
might be good to re-check the voltage across the battery to see if it
is still 10 volts (engine cranking with plugs installed). Since the
whole purpose of measuring the voltage at the starter was to compare
it
to the voltage reading at the battery, this is important.

Second, at one point the starter gear stopped popping up to engage
the
flywheel.

Did the starter gear ("pinion gear") spin rapidly during those times
when it didn't "pop up"? On an automotive starter motor, this can
be
indicative of a low battery. I'm not sure about the starter motor
design on this Briggs engine in this regard.