Was the engine cranking strongly right up to the point when the
stalling episode occurred, or was the cranking speed deteriorating
slowly over the period preceding the stalling episode?
This can be a sign of a weak battery, or bad cable connections, or a
starter motor starting to go bad. You said you had the battery
checked out, so I will assume they checked it properly and it is OK.
The troubleshooting procedures mentioned in the previous post should
help isolate it to either a cable problem or a starter problem.
However, as long as you have the plugs out, you should try one more
thing to help eliminate another possibility (valve problem). Make
sure the plug wires are far away from the spark plug holes and well
grounded so that there are no sparks. Have a helper crank the engine,
and put your thumb over each spark plug hole. You should feel
alternating compression and suction in each hole, and they should feel
the same. If they feel different, or you don't feel both compression
and suction, you've got a more serious problem inside the engine.
Ok, here is the update. I measured the voltage at the starter engine
terminal. 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?
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 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.
My son said that the engine slowly faded before stalling out.
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.
Second, at one point the starter gear stopped popping up to engage the
flywheel. I gently moved it by hand a few times. This seemed to
resolve the problem.
Ether Jones wrote:
9 volts when it should be 12 volts. That's a 25% loss--I would consider it
to be significant. If the battery is at 12 volts can you go directly from
the battery to the starter terminal using another lead (disconnect the
original lead to get it out of the system). For example, use a jumper cable
to make the connection. If the voltage still drops to 9 then consider it a
battery problem. If so, can you use the jumper cables to go from your car
battery to the tractor battery to verify?
Substantial drop in voltage at the battery under load is normal. 9
volts is at the low end of acceptable for a 12 volt system but still
PaulD already measured the voltage at the battery and gave that info in
a prior post. It was 10 volts, which is entirely normal. You might
want to read the rest of the thread to catch up on other details. The
test he reported on here was the voltage reading at the starter motor.
The purpose was to determine if the voltage at the starter motor (under
load) was the same as the voltage at the battery (under load). It
should be nearly so, if the cabling and connections are in good shape.
10 volts at the battery, and 9 volts at the starter seems to indicate a
problem in the cable connections.
By the way, it's a starter motor, not a starter engine.
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 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.
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.
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
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.
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.
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
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 solenoid? 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:
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 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:
Is it turning fast enough to start? Getting a spark?
Jumper in a car battery. Don't tackle the starter until you totally
eliminate that it might be battery.
If it is spinning fast enough to start try the suggestion of squirting
in some starter fluid. Personally I just use carburetor cleaner for
I think I did. He seems to be centered on heading for the starter motor.
I would prefer doing the test with a hefty battery that can take long
More important, I haven't seen anything about the engine firing when he
is doing those tests. Seems to me that regardless of how it cranks that
is what is important.
I would like to pull the head. Just wonder if that is difficult on that
engine. Usually pretty easy.
Since it died early, like you, I just can't believe it is the starter.
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
Read the rest of the thread, Don. The OP stated that the engine slowly
stalled out while his son was mowing the lawn. Then when he tried to
re-start, the cranking was slow. We're trying to determine if the two
are related. Very few single failure modes could cause both problems.
But a valve problem could cause both problems. If compression differs
greatly between the two cylinders it could indicate a valve problem.
So it's worth checking.
The compression doesn't have to be "too high" to cause a cranking
problem. If the exhaust valve is stuck shut in one cylinder, for
example (broken valve stem?), the starter motor has to work harder
because it's compressing on the exhaust stroke. This would cause
He already did that. It's described in an earlier post in this thread.
That's the current most likely answer (for the cranking problem) based
on the tests run so far. But before he runs out and buys and installs
a new starter motor, it was suggested that he rule out a valve problem
(which could cause the engine to crank slower, and would ALSO explain
the stalling described in the original post).
I spent some more time trying to figure this thing out and now I find
we need to backtrack again.
I tried the test again where you crank the engine with finger covering
the spark plug holes. When I cranked it using the starter I thought I
felt puffs and suction from both cylinders. This time I had my helper
just turn the flywheel while I had fingers over the holes. I got a got
puff and suction from one cylinder. On the other cylinder, however, I
got a puff, but little or no suction. So maybe Ether's original
thought is right about a valve problem? What should I do now?
Ether Jones wrote:
Pulling the head and replacing it looks fairly simple per the
repair manual. If I need to repair something in the valves, however,
I'll probably need to seek help from a friend who knows more than I do.
That looks fairly complex on this engine.
If I take off the head, what exactly should I be looking for. I
suppose if I find a stuck or poorly working valve, the next question is
what is causing the problem. For example, if I find a broken valve
stem, do I need to just replace it or is there more trouble shooting
involved to figure out why it broke.
With the head off, turning the engine over slowly you will see the
valves open and close. All closed during the compression and power
stroke. Only one open at a time during the intake and exhaust. Both
closed during the compression and power.
I once saw a valve stuck open to where just some penetrating oil and
twisting got it working again. And I have had them stuck open due to
carbon. A wire brushing fixed that one.
Your problem of getting suction but not exhaust sort of rules out an
open valve. More like one is permanently closed and that would likely
be something broke. If one is open you probably would not notice either
suction or puff.
Anyway, I have found it is normally a very easy task on a small engine.
And if nothing else gives me a chance to clean off any accumulated carbon.
How about spark? I have not noticed any mention of that.
I had an different problem just a short time ago. An old engine was
surging. Thought it might be ready for the scrap heap. The wire to the
kill switch ran through a little support hole on the casting. The wire
looked rather old and the cover brittle. Moving it around seemed to
change the surging. I put a good insulated sleeve over the wire and it
runs like normal again.
I haven't checked for spark yet because I really would not expect
the engine to start at its current cranking speed. Once I get the
cranking problem fixed, I'll trouble shoot any remaining problems.
Rich256 wrote: >Your problem of getting suction but not exhaust sort
of rules out an
Actually, I am getting exhaust, but not suction. Is that likely
caused by an permanently closed valve also?
I suppose the next step is to open up the head. When you say that
something is likely broke in the valves, is that a problem caused by
wear or am I going to need to look for another problem that might have
caused something to break? Could it be something as simple as a broken
spring? The engine was made in 1993 so I am not sure that I want to
invest alot of money in it. That is why I am trying to repair this on
my own, even though I am not much of a mechanic. I do think with some
help I could replace a broken spring or valve.
Ether or anyone else who can answer: Do you think the possible
valve problem is causing the cranking problem? Or do I still maybe
need a new starter?
In the event that I need to work of vavles, the repair manual says
that to get to the valve chamber I need to take off the carb and intake
manifold. I am not sure I need to do this. I think I could get to the
valve chamber by taking off just the crankcase breather. If so, I
think that would make any valve repairs a little easier. In any event,
if I need to do any work on the valves, I think I'll give a call for
help from a friend who has more experience in these matters.
It's difficult to say without quantitative information. Can you
quantify how fast the engine is cranking? Put a piece of masking tape
on the rotating screen. Is it slow enough that you can count the revs
while somebody else keeps time?
Or, how difficult is it to pull the starter? Your local parts store
that charges batteries for free sounds helpful. Do they have a test
stand for testing small engine starter motors?
Yes, definitely can count revs. Cranking is slow. I'll check with
the parts store and see if they have a starter motor tester. I have a
repair manual with spec for the starter motor.
I found that I can remove the starter motor quite easily without
messing with the flywheel. It is puzzling to me that the manual
suggests removing the flywheel to get to the starter. Doing so might
make removal marginally easier, but getting that flywheel off looks
like a big project unless you just the right tools.
I take it at this point everyone agrees that I need to remove the
head? I'll probably do that on Sunday unless someone can suggest
additional testing before doing so.
Ether Jones wrote:
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