# Motors and Motor-Driving/Chapter 9

CHAPTER IX
THE CAPRICES OF THE PETROL MOTOR
By the Hon. Charles S. Rolls
The intending owner of a motor-car will often say, 'What in the world should I do if the thing were to break down on a country road?' and the object of this chapter is to enable the novice en panne quickly to recognise the symptoms of his case (so far as the engine is concerned) and then at once to 'spot' the probable cause and remedy.
In order to make these remarks complete, I have been compelled to enumerate a very long and somewhat formidable list of evils, and lest a glance at this should frighten off any would-be motorist, it must be clearly understood that the list comprises possibilities as distinct from probabilities.
What is here said should therefore be looked upon in the same light as a veterinary surgeon's book on horses, and readers must not think that if they purchase cars all the troubles here mentioned would necessarily occur to the motor any more than they would imagine that all the diseases described in a horse-doctor's book would happen to a newly acquired horse. Many cars have been run by amateurs for thousands of miles without the occurrence of any trouble. In proof of this I may observe that a member of the Automobile Club recently stated that, although he had previously no engineering experience, he had run his car ten thousand miles without having to effect any serious repairs, and had experienced no trouble whatever except on two occasions, when the slight repairs necessary were done in a very short time.
​The chapter is divided into two parts, the first dealing with the 'Difficulties in starting,' and the second with 'Troubles on the road.'
Part I
THE MOTOR WILL NOT START
A petrol engine will generally start most easily with all the cold-air inlets closed, the usual procedure being to shut these air-holes or taps, then let a little petrol into the carburator, shake the float needle (if there be one) or inject petrol into the induction valves or through the compression tap on top of the cylinder, if such exists; then, the ignition tubes being red-hot, or the electricity switched on and ignition retarded, a few turns of the engine should suffice to set it going; if, however, it will not start, the trouble must lie in one of the following sources:—1. Ignition; 2. Carburation; 3. Compression; or 4. Moving parts.
1. Ignition.—Having satisfied yourself that the ignition is in perfect order (see Chapter VIII.), the fault must be in one of the three sources remaining.
2. Carburation.—Let us first take the Carburation. There are many little things which may militate against a healthy explosive mixture reaching the cylinders, and we will first enumerate the principal causes in brief as follows:—
(a) Wrong proportions of air and gas.
(b) Carburator flooded.
(c) Carburator starved.
(d) Cold weather.
(e) Stale petrol.
(f) Handle not turned fast enough.
To deal with these more fully:—
(a) The mixture of hot air, cold air, and petrel vapour should be varied in every possible way—see that an excess of air is not being drawn in through a crack in a pipe or loose coupling.
​(b) Too rich a mixture may be caused by the presence of too much petrol in the carburator; if this is so, turn off the petrol supply for a time and revolve the engine again with all air inlets wide open until the first explosions are obtained.
(c) Perhaps the cylinder cannot get any petrol vapour, owing to the nipple (in a float and jet type carburator) being stopped up. This nipple can be taken out with a special key and cleaned by passing a fine needle through it, taking great care not to enlarge the hole in the least degree. Possibly there is no petrol in the tank, or you have forgotten to turn it on, or the tank is almost empty and the car tilted by standing at the side of the road; push it over to the other side. One can tell if there is any petrol in the carburator by the position of the float needle, and the novice should provide himself with a diagram of his carburator.
(d) In cold weather, if the car has been standing idle for some time, considerable difficulty may be experienced in starting up. Petroleum spirit will of course vaporise far less readily at a low temperature than at a high one. Artificial heat is therefore the remedy, and this can be most easily applied by taking out the mushroom-piece in the carburator (if there is one), and warming it over the burners or otherwise; or warm petrol may be squirted into the cylinder or induction pipe or valve. In obstinate cases it may be necessary to warm the carburator underneath by means of a little cotton waste soaked with methylated spirit. There may be a slight flare up, but this will assist the carburation, and there is nothing to fear from it so long as the main supply cock has been carefully closed.
(e) Stale Petrol.—The petrol remaining in the carburator may lose its strength if the car has been standing a long while; it should be emptied out and refilled: A good plan when about to put away the car for some time is to stop the motor by turning off the main cock, so letting it use up the last drop of petrol in the carburator.
The petrol in the main tank may also become heavy in course of time, especially if free access of air is allowed to it. A small instrument called a densitometer is sold for determining the specific gravity of petrol; the best specific gravity for starting is ·680; if your petrol when tested shows heavier than sp. gr. ·700 it should be changed or the tank shaken up.
(f) Perhaps there is nothing wrong after all, except that you do not turn the starting handle fast enough to cause vaporisation. Remember that a few smart turns with the whole of your energy ​will be more likely to start an engine than hours of slow 'grinding.'
3. Having now ascertained that neither the Ignition nor the Carburation is to blame, if the motor still will not go we must look for the failure in either the compression or one of the moving parts.
Compression is the life and soul of a modern high-speed internal combustion engine.
When the engine is in proper working order, and being turned by hand, a considerable resistance should be felt at the alternate back stroke of each piston; this back pressure should require a considerable effort to overcome when the handle is being turned slowly. If the compression of any cylinder leaks, that cylinder will not give off its full power.
How to Locate a Leak of Compression.—If there is a loss of compression, a slight hiss will generally be audible when the handle is turned. In order to find out where the leak is, a lighted taper may be held over the cylinder in different positions, while the engine is being turned slowly; the flame will be turned on one side on meeting the leak; or soap and water may be painted about the cylinder head, and bubbles should soon indicate the presence of the leakage.
Possible Sources of Leakage.—(a) A leakage will generally be found at the junction of such fittings as the ignition tube, induction valve, valve cover, sparking plug, compression tap, or other attachment connected with the interior of the cylinder or combustion chamber—probably a washer blown out or a nut loose will be the cause.
Should, however, the leakage not reveal itself under the above tests, it is probable that
(b) the exhaust or inlet valves are 'pitted' or coated with deposit, and consequently permit a loss of compression past their seating; if this is so, they should be taken out and ground on their seats with fine emery powder and oil, or paraffin, till they bed properly; the engine may then have to be run for some time before the leakage ceases. See also that the valve springs have not grown too weak.
​(c) There is a possibility of the compression also blowing past the piston-rings. This can generally be detected by listening attentively with the ear close to the cylinder at fault, and turning the starting handle or fly-wheel slowly—a gentle hissing will be heard at intervals. The cause of this is generally the sticking of the rings in their grooves. The remedy is to wash out with paraffin so as to free them for their whole circumference. If they still leak badly, the piston should be taken out and new rings fitted, especially if the engine has been over-heated at any time, in which event
(d) the cylinder-head joint, if there is one, may have warped and the compression may be escaping from one cylinder to the other, and into the water space; water in turn will probably find its way into the cylinder, and being converted into steam, will interfere with the working of the engine and rust the valves. Little spots of rust on the valves will indicate what is happening, and the cylinder-head joint will then have to be re-made—a matter for an expert.
No Compression at all.—If on trying to start the motor no compression at all is felt on one cylinder, there may be a valve stuck open through a breakage or gumming (see later), or else the ends of the piston-rings may have by chance arrived opposite one another, thus allowing the compression to slip through the spaces. When this occurs, the rings should be freed by letting in paraffin and running the engine a bit on the other cylinder or cylinders if possible; the rings will probably soon change their position—they are purposely allowed to move round so as to wear evenly.
Apparent Excessive Compression.—There may, especially on a cold morning, appear to be so much compression that the engine can hardly be turned; this stiffness is really due to the drying of the oil on the walls of the cylinder. To avoid this a copious dose of paraffin should always be injected when stopping the car after a day's run, and a few turns given to the engine by hand.
Note.—It is most essential for every motorist to insist on having proper and convenient means fitted on his car for washing the cylinders with paraffin or petrol, both to facilitate starting up and to keep the piston-rings in good order.
​Back Firing.—I have said that a considerable resistance should always he felt when turning a motor slowly by hand; sometimes, however, the innocent motorist, when endeavouring to put his engine into motion, receives something considerably more than a mere resistance. He may get a kick from the handle which will give his arm a nasty jar, or possibly sprain his wrist. These 'back fires' are the result of what is called 'premature ignition,' and therefore belong strictly speaking to the chapter on 'Ignition.' I may merely remark that they are due to the spark-timing gear being too much advanced, the platinum tubes being too long, the burners being too close in, faulty opening of the induction valves, overheating of the motor, or ignition tubes being too hot; in the last case the burners may be turned down to allow the tubes to cool momentarily and turned up again when the motor starts. In the other cases the remedies are obvious.
4. Moving Parts.—Having exhausted the possible causes of refusal to start except those consisting of some mechanical fault, we will now see what moving parts could go wrong, and so cause all the trouble.
(a) The mechanism for operating the electric ignition is liable to many little derangements (see Chapter VIII.).
(b) A broken exhaust-valve stem or a broken or displaced spring will often be difficult to observe; a valve may have stuck open through stiffness or through something getting under its seat. The exhaust-valve gear should be carefully watched to see that all the valves work regularly and to their full extent.
(c) Stiffness in the accelerator or governing gear, or a dislodged key, pin, or feather may also hinder the lifting of the exhaust valves, or on some engines prevent the throttle from opening itself fully.
(d) The simple mechanism adopted on some cars to engage the starting handle with the motor will sometimes give out, so that the handle will not turn the motor. In cars of the Panhard type the handle is made to engage with the engine by pushing a small bevel-ended tongue in against a small pin put ​through the end of the crank-shaft; a bad 'back fire' may cause this pin to sheer off or bend and jam the tongue. The novice should be shown the way to get at this mechanism so as to know how to renew the pin or tongue. If the starting gear fails at an awkward moment, the car may be started by putting in the third or fourth speed and pushing the car with the friendly aid of a few lookers-on.
PART II
ROAD TROUBLES
We will now pass on to Part II., dealing with possible troubles encountered on the road, dividing this section into—
1. Motor stops.
2. Motor nearly stops and then goes on again.
3. Motor will not pull well.
4. Motor will not govern or 'cut out' properly.
5. Unusual noises.
MOTOR STOPS COMPLETELY
This may be divided into—
A. Overheating.
B. Starvation of carburator.
C. Carburator flooded.
D. Burners going out.
E. Mechanical reasons.
A. Overheating.—The most serious cause of a stoppage on the road is undoubtedly overheating, which causes the lubrication to burn up and the piston to expand and grip or ' sei/e ' in the cylinder. This matter of overheating should now be divided into its various causes, viz.:—
| Cause | 1. Water circulation stopped. | |
| " | 2. Water all lost. | |
| " | 3. Faulty lubrication. | ​ |
| Cause | 4. Water entering cylinder. | $\scriptstyle {\left.{\begin{matrix}\ \\\\\ \\\ \\\ \ \end{matrix}}\right\}\,$ very unusual. |
| " | 5. Too powerful a charge. | $\scriptstyle {\left.{\begin{matrix}\ \\\\\ \\\ \\\ \ \end{matrix}}\right\}\,$ very unusual. |
| " | 6. Incrustation of jackets. | $\scriptstyle {\left.{\begin{matrix}\ \\\\\ \\\ \\\ \ \end{matrix}}\right\}\,$ very unusual. |
Cause 1. Water Circulation Stopped.—Of these the cessation of water circulation for cooling is the most important. It must be the result (a) of the pump ceasing to act through bad adjustment of its driving-gear, or through its valves or cogs jamming; its spindle being seized or bent; the interior fan worn or unkeyed; the friction wheel unkeyed, or its tyre worn out or come off.
As regards the adjustment of the driving-gear of a centrifugal pump driven by friction, the friction wheel and spindle should revolve freely when the pump is pulled away from the fly-wheel. It should be adjusted so that the spring presses it lightly but firmly against the fly-wheel; cafe should also be taken in packing the glands of these pumps, for they run at a very high velocity; a very slight leak of water, however, is advantageous for lubrication.
(b) The blockage of a water-pipe or passage will also impede the circulation, or
(c) There may be an air or steam lock in the pipes. The best way of getting rid of an air lock is to open all cocks and plugs in the water system and run the engine, filling up the tank and water jackets to make up what is running out. This will eventually expel any air, and the water will circulate freely.
Cause 2. Water Lost.—If all the water has been lost on the road through the breakage of a pipe or the opening of a plug or tap, or loosening of a joint, and no water is near, you can continue your journey spasmodically by allowing the engine to cool down, then run on a mile or two with the bonnet open or off until it shows symptoms of overheating again, when stop, paraffin your cylinders, and wait another half-hour. The pump of a car has several times been known to have been carried away by contact with a dog; in one case there was no trace of pump or dog except a tooth which the unfortunate animal left in the back tyre.
Note.—Always carry rubber tubing to repair ruptured pipes.
Cause 3.—If the overheating has been caused by fan It v lubrication, it is probable that this is due to inattention to the lubricators.
Remarks as to Lubrication.—It should be ascertained from the makers how many drops a minute are required for the proper ​lubrication of the engine and it must be remembered also that in cold weather when the oil is thick a different adjustment will be necessary from that found suitable in warm weather. It is most important that the lubrication should be regular, and with good oil but not too much; for too much oil will spoil the sparking plugs, clog the valves, and interfere with the explosive mixture. For this reason the lubricators should always be carefully closed when stopping. If a Dubrulle mechanical lubricator is used, examine the ball valves sometimes, and do not trust entirely to the sight feed. If a pressure type lubricator is used, see that the stopper is tight, for if the pressure from the exhaust leaks the lubrication will stop and in some cars the supply of petrol too.
It sometimes happens that an oil pipe or hole is stopped up and wants cleaning, or perhaps the plug at the bottom of the crank chamber has come unscrewed with the vibration and dropped off, losing all the oil, in which the cranks should always dip. The proper amount of oil for each crank case is generally at least half a pint; an extra lubricator to the cylinders or base chamber should always be fitted, so that a little extra oil can be fed in by hand, if there is any doubt about the engine getting enough.
The following are additional causes of overheating. They are, however, of very rare occurrence:—
Cause 4.—The head joint may leak and admit water into the cylinders.
Cause 5.—In some engines if the throttle is kept full open, so as to admit too powerful a charge of gas, overheating will result.
Cause 6.—Finally, a thick incrustation on the walls of the water jacket, due to the use of bad water, will prevent the cooling water from taking up the excess of heat from the cylinder.
Remarks on Overheating.—How to tell when a Motor is Overheating.—The symptoms are:—
​1. The driver can generally detect a slight smoke rising from the engine, and a smell of burnt paint and burnt oil.
2. A peculiar tapping sound becomes audible.
3. The engine will continue firing for a few revolutions after the current has been switched off or the burners extinguished.
4. Steam issues from the cooling water or the water blows out of the overflow pipe.
What to do when the Motor Heats.—As soon as any of the above symptoms are noticed—
(1) The motor should be stopped at once.
(2) Paraffin should be copiously injected into the cylinders and the engine turned by hand to free the piston-rings.
(3) The parts should then be allowed to cool.
(4) Change the exhaust springs.
N.B. Do not pour cold water into the cylinder jackets, for fear of cracking them, but rather pour into the tank so as to warm the water before it reaches the cylinders.
Dangers of a 'Seize.'—Overheating of the engine to this extent should be guarded against, for it is liable to cause scoring of the cylinder walls, and may warp the cylinder-head joint (if there is one), which will necessitate re-making the faces a tedious and difficult task. The exhaust-valve lifters may become bound, the excess of heat will also cause the valve-springs, piston-rings (and possibly the occupants of the car), to lose their temper; apart from the above no damaging effects are usual.
Precautions.—To enable the driver to verify the water circulation a 'manometer ' should be placed on the dashboard to indicate the pressure of water, or a tap or float arrangement may be connected with the piping, so as to show whether the circulation is all right. During hard frost this is especially important, for should the circulation cease, the radiator, a pipe or even the water-jacket itself, may be easily burst by the frost.
B. Starvation of Carburator.—A motor may stop from other causes besides overheating—for instance, no petrol may ​reach the carburator. One of the following will probably account for this:—
Cause 1.—Petrol supply tap has turned itself off by vibration against tools, &c.
Cause 2.—No pressure to feed petrol.
Cause 3.—Supply pipe, filter or jet in carburator blocked with a piece of waste, asbestos, dirt, or deposit.
Cause 4.—If the tank is nearly empty, and a very steep hill is encountered, the carburator may be too high for the petrol to run into it; the remedy is to pump air pressure into the tank. '
Cause 5.—A union may be disconnected, pipe broken or plug under carburator dropped off, and you have lost all your petrol, or perhaps the tank has simply run dry. Remedy: leave your friend to sleep on the car, take list of petrol depôts, and make your way to the nearest town; if you cannot get any proper spirit, bring out some common benzoline of about ·700 gravity and take a spare tin of petrol on the car next time.
C. Carburator flooded.—If, on the other hand, there appears to be too much petrol about, and it is running out of the carburator, the float needle is stuck or bent, or the float has punctured and petrol got inside it. In the latter case, take out the float, make a hole large enough to let out the petrol, and carefully solder up air-tight again.
D. If your burners go out when you start the car, as is sometimes the case, it is due to the jerk of the car sending the petrol from the burners back towards the tank. To obviate this, the tap should be opened as little as possible.
E. If the car stops from some mechanical cause, the reason may probably be found in the former section 'Motor will not start,' or in the chapters dealing with Transmission or Ignition. Most probably it will be due to: —
i. A broken valve.
ii. Broken or misplaced spring,
iii. Valve-gear not operating properly.
iv. Something has lodged on the face of the valve, holding it open. I have known the cottar of an inlet valve and parts of
FITS AND STARTS
If a motor nearly stops and then goes on again, it is generally due to temporary starvation of the carburator. There is probably some water, oil, waste, dust, asbestos, dirt, or deposit of some sort at the ingress of the spirit, which, however, sometimes frees itself. To avoid these troubles petrol should never be poured into the tank except through a funnel fitted with a very fine gauze strainer or a piece of muslin. I have known a little particle of matter dance about in the mixing chamber, and once in a way it would lodge on top of the spray-nipple for a time.
It should be remembered that air must always find an inlet to the tank in order that the petrol may flow out freely, and considerable difficulty has been caused by the tiny vent-hole which is drilled in the stopper of the main tank becoming blocked up by some dirt or an overcoat lying on it under the cushion. It may happen that air can get to it when you are starting up; then when you sit down on the cushion the hole becomes air-tight and the engine gradually stops.
MOTOR WILL NOT 'PULL' WELL OR MISSES FIRE
We will treat this malady under the following headings:—
A. Ignition.
B. Compression.
C. Carburation.
D. Too much oil.
E. One cylinder will not work at all, and
F. Irregular missing.
A. Nothing is so annoying as to drive a motor which is continually missing fire or has a 'fit of the slows.' The fault is usually with the ignition—the platinum tubes are not hot ​enough, or are dirty inside or outside, or the passages leading to them are clogged. When exhaust pressure is adopted for feeding the burners with petrol, the pressure-valve sometimes refuses to act and lets the pressure out. Remedy for this:—Grind the little valve or change the spring, and see that its lift is just one millimetre. Perhaps there is oil on the sparking plugs, or the battery is run down, or the timing is not correct, but we are here trespassing on to the province of 'Ignition' (see Chapter VIII). If the root of the difficulty is elsewhere, perhaps
B. The compression is poor (see 'Motor will not Start') or
C. The carburation is not good:—
Cause 1.—The proportions of air and gas are not well adjusted.
Cause 2.—The petrol is stale.
Cause 3.—Petrol cannot get free access to the carburator (see 'Fits and Starts').
Cause 4.—The gauze through which on some cars the air is sucked is blocked with dust, or the gauze which is sometimes fitted into the induction pipe is dirty, or that fitted between the exhaust and the pressure valve (in cases where a branch of the exhaust is utilised to maintain pressure in the petrol or lubricating tanks) is foul.
Cause 5.—A pipe-joint is loose or has a hidden crack through which an excess of air enters.
See also 'Carburation,' pp. 165 and 166.
D. Too much lubricating oil is used, causing (i) valves to stick; (ii) a deposit on the sparking plugs; and (iii) an unhealthy charge in the cylinder. Excess of oil reveals itself in the form of smoke issuing from the exhaust.
E. One cylinder does not work at all. If one cylinder misses fire regularly, it is probable that
i. The exhaust or induction valve has given up the ghost, or
ii. The nozzle for supplying that cylinder with spray is blocked.
F. If, however, the miss-firing is irregular, and none of the defects aforementioned are found, we must look to less common sources for the difficulty.
​How to find which Cylinder Misses.—Endeavour first to ascertain which cylinder is the culprit. One method of doing this is to place your hand on each exhaust pipe while the engine is running. You will then get a bad burn from every one except that belonging to the faulty cylinder. A more convenient way—if electric ignition is fitted—is to stop the working of three out of four of the induction coils, changing about until you find the one that is at fault. It may be, however, that your engine has only one cylinder, or that all the cylinders miss occasionally.
Let us take the various possible causes of the difficulty.
Cause 1.—Be sure that the governing gear is working properly, and that the governor does not cut out one cylinder when it ought not.
Cause 2.—The induction valve may be worn, and opens too much.
Cause 3.—Exhaust valve lifters worn and do not lift enough.
Cause 4 (rare).—They have expanded through being overheated, and open too much.
Cause 5.—A spring displaced.
Cause 6.—The exhaust or induction valve springs are not strong enough to close quickly, and an exhaust valve may sometimes open on the suction stroke.
Cause 7 (rare).—The mushroom-shaped fitting called the diffuser, which is part of the small disc screwed into the top of the carburator, may be too near or too far from the jet of petrol.
Cause 8.—Or the size of the nipple through which the jet is sucked is too large or too small. It is very seldom that this should be touched, and its adjustment must be made with extreme delicacy, by the aid of a watchmaker's brooch-needle. It is always best to make any experiments on a spare nipple, and not to touch the one that is in use, so that if unsuccessful you may put back the old one, otherwise the last state of your carburation may be considerably worse than the first.
Cause 9 (rare). Freezing of the carburator. Trouble will sometimes arise through the carburator freezing, even in warm weather. The remedy is to fit a pipe to convey to it air heated by the exhaust or the burners.
​There are still a few but extremely improbable causes for irregular firing:
Cause 10 (rare).—There may be too much play worn in the cogs of the valve gear or ignition gear. The remedy is to advance one tooth.
Cause 11 (rare).—The cog wheels of the 'two-to-one' gear may have been put together wrongly by a repairer.
N.B. Always make your own marks when taking these wheels apart, for the existing marks may not necessarily be correct. The makers often find a better position for the teeth to engage after one set of marks have already been made.
Cause 12 (rare).—It has also happened that the key or feather by which a gear wheel of the ignition or valve mechanism is keyed on to its shaft has sheered, and the wheel has moved round on its spindle, causing firing to take place at the wrong instant, and very erratic behaviour in consequence.
Cause 13.—For reasons previously explained, if water can find its way into the cylinder, misfiring may result.
Finally, remember that if your engine is misfiring or pulling badly, the fault may of its own accord very likely disappear altogether after a little running.
ENGINE RACES, I.E. GOVERNOR WILL NOT WORK
Evidently something wrong with the governing gear. What?
Cause 1.—The cam, which, by means of a small fitting which resembles a hammer, throws the exhaust-valve lifters out of action, is keyed to its shaft by a small screw; if this works out, as it sometimes does, the cam will move about where it likes, and leads to the fault in question.
Cause 2.—Similarly if the 'hammer' gets loose or is worn, the same result will follow.
These remarks refer to the engines of the Daimler and Panhard type.
Cause 3. In these motors the governor is usually arranged to cut out one or two cylinders before the rest; if much wear has taken place in this mechanism the trouble in question may arise.
There are also springs whose function it is to bring back the exhaust lifters into action after they have been 'cut out' by the ​governor. If this mechanism has been roughly fitted or has had much wear, I have often found that the ends of these springs should be slipped off their knobs for the engine to govern properly; and that if they are in place one cylinder may refuse to cut out at all.
Cause 4.—Of course if any of the delicate spindles, &c., connected with the governing mechanism be strained in any way, or are allowed to get dry for want of oil, the same trouble may be expected.
If the governor goes wrong at an awkward moment in the traffic, and the engine begins to race, it may be controlled by switching off and on, or retarding ignition, admitting an excess of air, or the exhaust-valve lifters may be thrown out by hand.
UNUSUAL NOISES
Regular.—If an unusual but regular puffing noise (external) is heard, which keeps time with the engine without apparently affecting its running, it is clear that an exhaust joint has given out somewhere between the exhaust valve and silencer. IF the rupture is near the engine, the exhaust gases may slightly interfere with the burners and the mixture, but otherwise no harm will be done to the motor, though the noise may frighten passing horses considerably.
A regular but unusual tapping coming from the engine indicates
i. Something loose or broken.
ii. Too much advance in ignition, or
iii. Engine about to seize through overheating.
If a squeak is heard anywhere instant attention should be paid to it, otherwise much harm may be done. A slight squeak is often very difficult to locate, and turns out sometimes to be perfectly harmless; a squeak has been traced to the rubbing of the bonnet against something inside it, to the shaking of the radiator, vibration of lamps, and such like causes, which, though trivial when found, are sources of great anxiety to a careful motorist.
I have had a distinct whistling sound produced by the rapid suction of air through a brass tap at each revolution of ​the engine. This took a long time to discover. A slight leak of compression will also sometimes produce a squeak at each explosion.
Irregular.—Popping Noises in the Carburator or Induction Pipes.—These are minute and harmless explosions caused by:—
i. Induction valves opening too much, or
ii. Sticking, or
iii. Their springs being too weak.
iv. Cold ignition tubes.
v. Retarding the ignition suddenly at high speeds, or
vi. Bad carburation.
Bursting Noises (irregular} coming from the Engine.
i. These indicate:—Burst joint at valve cover, sparking plug, or ignition tube. Spare washers specially made must always be carried to rectify these.
ii. A platinum tube may have burst. Spare ones should always be carried. What to do if Ignition Tube bursts and you have no spare one. If you have no spare one, the hole of the old one should be closed up as much as possible with a small hammer, then replace the tube with the hole in such a position as not to blow out the burner or its neighbour. If you can keep the burners alight progress can thus be made. Failing this, the faulty tube or the hole leading to it must be blocked up, and the car run home on the remaining cylinder or cylinders.
iii. Loud Report in Exhaust.—This is due to several unexploded charges having collected in the silencer, and being ignited by the incandescent products of the next fired charge; switching the electric ignition off and on will often produce this, so may a sudden retarding of ignition, or a semi-cold platinum tube.
There is no danger in these explosions—startling as they seem—beyond the risk of splitting the exhaust box or pipe.
RÉSUMÉ
It will now be seen that troubles may arise from any of the six following sources:—
| Ignition | Lubrication |
| Carburation | Circulation, and |
| Compression | Moving parts |
I have tried to classify all possible troubles according to their symptoms, so as to make it easy for the novice quickly to locate the root of evil and rectify the fault.
CONCLUDING ADVICE AND REMARKS
If your motor works well, leave it alone, although it may never seem fast enough. Many troubles arise from interference and undue curiosity.
Remember that petrol is a highly volatile and inflammable liquid; its vapour is equally dangerous.
Make sure that all petrol connections and unions are taut.
If you have a flare-up, immediately close the supply cocks or let off the pressure, take off bonnet to save the paint, and smother the flames, or let them burn out. Water should only be thrown to save woodwork.
Do not pour petrol near a naked light; it is prudent to extinguish the burners when filling the tanks of the car.
Do not spill the petrol over your clothes and then strike a match to light your pipe.
Do not go out even for a short run without complete equipment of tools, spare parts, petrol, and repair outfit, or you may be back late.
Do not let a willing ostler fill up your petrol tank with water.
Do not leave the water in your car on a frosty night, except with 20 per cent, of glycerine in it.
​Do not start away with your brake hard on and wonder why the motor is not pulling.
Do not pedal your tricycle for half an hour before remembering the plug switch, unless the doctor recommends it.
Do not let the starting handle fly off and hit you on the chin, and
Do not trouble to turn on the petrol tap if there is none in the tank.