HUNTING TROUBLE
Ordinarily the fellow who starts to hunt trouble finds it quicker
than he expected, but not so with the automobilist; when he starts to
hunt trouble—in the car—it seems to be a very demon for eluding the
searcher. Trouble will hide in a tiny piece of carbon lodged under a
valve or between spark-plug points, in a wire that has jarred loose, in
an interrupter point, a piston ring, a gas pipe—oh, in the most secret
and insignificant place—in size—and just defy one to ferret out the
demon. One learns that the insignificant things are really the most
important at times.
Yet most troubles incident to the operation of a motor car may be
located very quickly if one will but go after them in a systematic way,
and not wander aimlessly about the engine and other parts. The hardest
thing a driver has to do when the engine stops or acts up is to divest
himself of the idea that he knows just what the trouble is. He is sure
he can fix it in a minute and he putters around a long time before he
makes up his mind that it is something else and it takes a lot of time
to prove that to some persons.
The best way to go about it is to start without preconceived ideas as
to what the trouble may be, and follow a system, which is really a
process of elimination. Remember that to start a gasoline engine three
things are necessary—gasoline, compression, and a spark at the right
time, and that to keep it running it is necessary to have water for
cooling, unless it be an air-cooled engine, and oil for lubrication.
If the engine stops on the road and pressing the starter pedal fails to
start it, or if one or two cylinders miss fire, the first thing to do
is to get the crank out of the tool kit and crank over the engine. If,
with the gears in neutral, the engine cranks over hard, it indicates
a lack of lubricating oil, or a lack of water, which has allowed the
engine to reach a temperature where the lubricant fails to perform its
work. If the engine turns over fairly easy, it is not necessary to look
for oil or water trouble.
The next test is for compression. If the driver is not experienced
and is unable to tell simply by the resistance to the starting crank
whether each cylinder has compression, he should open all petcocks
except on one cylinder and turn the crank two revolutions, noting
if there is a resistance for one-quarter of a revolution in the two
complete turns. Compression occurs only on one stroke of the piston
in the four-stroke cycle. Each cylinder should be tested in a similar
manner, opening all petcocks except on the cylinder being tested; see
if the compression is practically equal in all cylinders.
If one cylinder has very weak or no compression, the trouble will be
found usually in the exhaust valve. First examine the push rod to
see if there is clearance between it and the valve when the valve is
supposed to be closed; if there is, the valve must be lifted out and
the valve and seat inspected for carbon. Sometimes a piece of carbon
will lodge on the valve seat and, due to the hammering of the valve,
will become fastened to valve or seat. For temporary repair generally
it can be scraped off with a knife, and the valve be ground in upon
reaching the garage.
If the trouble is not in the exhaust valve, it might be in the inlet
valve. In some types of engines the valve head may break off and
get into the cylinder and when the piston comes up punch a hole in
the piston head. A petcock may be loose so that it will jar open
sufficiently to affect the compression and so cause the cylinder to
miss fire. These troubles usually are confined to one cylinder and not
to the whole engine.
The gasoline is the next to be inspected. Is there any gasoline in the
bowl of the carburetor? This may be determined by inspection, opening
the drain cock, or “tickling”—flooding. If not, examine the gasoline
tank and see if there is a supply; then see if the shut-off valve in
the line leading to the carburetor is open; if so, drain the bowl of
the carburetor to get rid of water or possible dirt. To check the
possible clogging of the gasoline pipe, or carburetor screen, notice if
the bowl fills up again in a reasonable time.
Do not adjust the carburetor. If the engine has been running, it
is practically certain that the carburetor has not gotten out of
adjustment. Inspect the intake pipe, or manifold, to see if it has been
loosened by vibration. If the engine still refuses to run, put about a
tablespoonful of gasoline in each cylinder and crank over the engine.
If this runs the engine for a few revolutions, it indicates that the
trouble is in the gasoline system and leaves but the spray nozzle,
which may have dirt lodged in it, or the auxiliary air valve stuck, as
the remaining causes of trouble. Sometimes turning the needle valve
a full turn and then turning it back exactly where it was will remove
an obstruction at that point. Care should be taken in this to get the
needle valve set as it originally was.
Next inspect the ignition system. The first thing to do is to loosen
one of the wires from a spark plug and lay it so the bare end will be
1/8 inch from the base of the plug, and have someone crank the engine
by hand or with the starter. If a spark does not occur, go first to
the interrupter points and short circuit the fixed point with a screw
driver or other metal tool and see if there is a spark when the engine
is cranked. Examine the points for dirt and see if they come together
and open properly. Then examine the condition of the battery, testing
it. Examine the connectors on the battery, which sometimes jar loose;
examine the wires leading to the interrupter and switch; see if they
are loose or broken or short-circuited. This need not be done if a
spark shows at the interrupter.
Examine the distributor for moisture or dirt and see if the wires
have become loose. If a magneto only is used, it is a simple matter
to see if the interrupter points are making and breaking properly and
if the distributor is clean and dry. If these appear to be all right
the trouble doubtless is in the armature winding or the condenser and
cannot be repaired upon the road.
The wires to the plugs may be burned or short-circuited. If, with
an apparently good spark, you have compression and there is mixture
passing into the cylinders, the trouble may be in the spark plug. To
test a spark plug it is necessary to remove it. Widen the gap to 1/8
inch and lay the plug with wire attached upon the cylinder; crank the
engine and see if a spark jumps the gap. Widening the gap is necessary
because the spark will not jump so far under compression as in the
open air. If it does not jump, the plug may have a broken insulator
porcelain or need cleaning. If uncertain about the condition of the
plug, exchange it with one in another cylinder which is working
properly. An extra set of plugs should be carried to replace those
which become dirty; cleaning should be done in the garage.
This covers most of the usual troubles experienced on the road. There
are, of course, a great many other possibilities, but if these tests,
carefully made, do not disclose the cause of the trouble, the novice
had better send for a garage man. If one or two cylinders miss fire,
the trouble is most likely to be caused through lack of compression or
a short-circuited spark plug. If the engine refuses to run, the trouble
is most likely to be due to lack of gasoline, or failure of battery or
magneto.
The general rule given herewith should be copied and pasted under the
hood, or carried in an envelope in the tool box for ready reference.
It may save much time and trouble when far from a garage. Carefully
followed, it should locate almost any trouble likely to be experienced,
and it is the locating, not the fixing, which takes time.
The chart on the next page was evolved out of the experience of years
at the school and elsewhere. It will be found a guide in hunting
trouble:
+---------------------------------------------------------------+
| THE Y. M. C. A. GENERAL TROUBLE CHART |
| |
| Above all _remove nothing from the engine_ except as directed |
| to test rules. |
+========+=========+============================================+
| |1. | Is tank full? ARE PIPES CLEAN? |
| Needed | GASOLINE| Is Carburetor clean? If Carburetor |
| | | needs adjusting, do it, otherwise LEAVE |
| to | | IT ALONE. Does Manifold leak? |
| +---------+--------------------------------------------+
| Make |2. | To test--Open all petcocks except |
| | COMPRES-| the one on cylinder to be tested; |
| an | SION | crank engine, noticing how strong |
| | | the compression is in each cylinder, |
| Engine | | in turn. |
| +---------+--------------------------------------------+
| Run |3. | A. Test for a spark by taking the |
| | IGNITION| wire off any plug; hold wire about 1/8″ |
| | | from plug; crank engine with switch |
| | at | on. Spark should jump to plug. |
| | +--------------------------------------------+
| | the | B. _Are the Batteries run down?_ |
| | | Does the vibrator (if any) buzz? Is |
| | right | timer clean? Does timer rotor make |
| | | _good_ contact? |
| | time +--------------------------------------------+
| | | C. Are any WIRES loose, burnt, wet, |
| | | broken, or short-circuited? Are spark |
| | | plugs clean and are points 1/50″ apart? |
| | +--------------------------------------------+
| | | D. Does MAGNETO armature revolve? |
| | | Is safety spark gap clean. |
| | | Are Interrupter points clean and adjusted |
| | | good contact? Is Distributor clean? |
| | | Is Distributor Rotor loose, broken, or |
| | | making poor contact? |
| | +--------------------------------------------+
| | | E. Check Magneto wires as per “C.” |
+========+=========+============================================+
| NOTE—Loose wires and terminals, neglected batteries, and |
| dirty gasoline cause much trouble. |
+---------------------------------------------------------------+
| TO KEEP A GAS ENGINE RUNNING, cooling and lubrication and |
| a free exhaust are necessary. |
+---------------------------------------------------------------+