Motor-car principles; the gasoline automobile

by Roger B. Whitman

IGNITION. Jump spark, with battery, timer and coils.

To test, revolve crank-shaft twice, listening for vibrators.

All vibrators sound normal, primary circuits O. K. unless timer has slipped on shaft.

Vibrator should begin to operate as a piston gets to top center of compression, with spark lever retarded.

One or more vibrators sound normal, showing that battery connections, lead and ground wires, and battery are O. K.

To test coils, short circuit the timer by making contact between primary terminal of coil and ground.

Vibrator normal, coil is O. K., look for

Interruption in timer circuit.

Blade moves, but will not vibrate.

Punctured condenser [([1])].

Short circuit at vibrator.

Vibrator does not operate.

Faulty adjustment.

Too stiff.

Will operate only with strong battery.

Excessive sparking at vibrator, and battery exhausts rapidly.

Too weak.

Feeble secondary spark; misfiring with slightly corroded contacts.

Contacts corroded.

Contacts stuck.

Vibrators do not operate.

Open switch; vibrator trouble.

Trouble in battery or in primary circuit.

To test, make momentary contact from switch terminal to ground.

Bright spark, battery lead and ground wire O. K.

Weak or no spark.

Break in battery connections, lead or ground wire.

Battery exhausted or dry cells polarized.

TEST 1. Alternate test, prime cylinders with a few drops of gasoline, close relief cocks, and crank. Explosions show ignition to be O. K.

To test secondary, disconnect spark plug leads, support them ⅜ inch from engine ground and crank.

Good spark, O. K.

Weak spark.

No spark.

Vibrator trouble.

Plug short circuited, fouled, oily.

Points too far apart—should be 1/32 inch.

Short circuit in secondary.

Broken condenser connection [([1])].

Shown by brilliant sparking at vibrator.

IGNITION. Make and break, with low tension magneto. Use Test 1, cranking briskly.

Explosions.

Ignition O.K. unless

Magneto is out of time and igniters incorrectly adjusted.

Should break circuit at top center of compression when spark is retarded.

No explosions.

Short circuit.

Insulated bridge on magneto.

Switch or switch lead.

Bus-bar or bus-bar lead.

Igniter insulator broken.

Igniter stuck closed.

Broken spring.

Tappet stuck in guide.

To test operate by hand.

Open circuit.

Magneto broken down.

To test magneto, disconnect magneto lead from bus-bar and hold free end in bare fingers, or

Shock or spark.

Magneto O. K.

TEST 2. Hold free end against teeth of metal gear and crank briskly.

No shock or spark.

Fouled collecting brush.

Armature burned out [1].

Fields demagnetized [1].

To test, unmesh gear, revolve armature by hand. If fields are O. K., armature should turn perceptibly hard twice in each revolution.

CARBURETER. To test, hold lighted match over open relief cocks while engine is cranked briskly.		Mixture ignites.		Proving that carbureter is doing its duty.
		Mixture does not ignite. Operate primer to flood float chamber.		Gasoline drips from spray nozzle.		Mixture too rich.		Insufficient air.		Faulty adjustment of air valve.
										Clogged inlet pipe.
										Dust on inlet pipe screen.
								Leaking float valve.
								Float too heavy.		Soggy (if of cork) [([2])].
										Punctured (if of metal) [([3])].
								Faulty adjustment of float.
						Mixture too poor.		Too much air.		Faulty adjustment of air-valve.
										Leaks in inlet pipe.
										Faulty adjustment of float.
								Water in gasoline.
				No drip from spray nozzle.		Clogged spray nozzle.
						Clogged float valve.
						Clogged fuel feed.
						No gasoline.
						Empty tank.
						Closed supply cock.

IGNITION. Jump spark with low tension magneto and coil (Eisemann, Remy, Splitdorf, etc.)

Proceed as in Test 1, cranking briskly.

Explosions.

Ignition O. K. unless magneto is out of time. Should be reset.

Sparks in safety spark gap.

Interruption in secondary circuit.

Too wide a gap at plugs (should be from 1/64 to 1/32 inch).

No explosions.

Primary circuit open.

Primary short circuit.

Magneto broken down.

To test magneto, disconnect primary lead to coil and proceed as in test 2.

Shock (or spark), magneto O. K.

No shock (or spark).

Interrupter short circuited, wet or oily.

Field demagnetized [([1])].

Condenser broken down (shown by brilliant spark at interrupter) [([1])].

Coil broken down.

To test primary winding of coil disconnect ground wire and proceed as in second part of test 2.

Spark, winding O. K.

No spark.

Winding broken [([1])] down or short or open circuited.

To test secondary winding of coil, disconnect spark plug leads from magneto and crank briskly, watching for sparks at safety spark gap.

Sparks, look for

Plugs short circuited.

Fouled.

Insulation broken down.

Fused metal bead at points.

Secondary short circuit [([1])].

Leads short circuited.

Ground circuit open.

No sparks, winding broken down.

IGNITION. High tension magneto (Bosch, U. & H. Lacoste, Witherbee, etc.

Proceed as in Test 1, cranking briskly.

Explosions.

Ignition O. K. unless magneto is out of time. Should be reset.

Sparks in safety spark gap.

Break in secondary circuit.

Too wide a gap at plugs (should be from 1/64 to 1/32 inch).

No explosions.

To test magneto, disconnect spark plug leads from distributor and crank briskly, watching for sparks at safety spark gap.

Sparks.

Magneto O. K.

Look for short circuits in

Spark plugs.

Fouled.

Insulation broken down.

Bead of fused metal between points.

Switch lead.

Switch.

No sparks.

Corroded interrupter contacts.

Interrupter stuck.

Armature burned out [([1])].

Condenser broken down [([1])].

Field demagnetized [([1])].

FUEL FEED SYSTEM.		To test, open drain cock at carbureter.		Gasoline flows.		System is O. K.
				Gasoline does not flow.		Gravity feed.		Clogged vent hole in filling cap.
								Clogged piping [([4])].
						Pressure feed.		Sufficient pressure in tank.		Clogged piping [([4])].
								Insufficient pressure in tank.
										Leaking tank or piping.
										Leaking filling cap.
										Stuck relief valve.

COMPRESSION.		To test, crank engine slowly, noting resistance, which should be the same in all cylinders. (Do not confuse constant mechanical resistance with intermittent resistance of compression). Inject oil into faulty cylinder.		Improved compression indicates		Stuck piston rings.		Douse cylinder with kerosene and alcohol ½ and ½ to cut carbon.
						Worn or scored piston rings.
						Scored cylinder walls.
				No improvement in compression indicates		Worn or pitted valves.
						Leaking spark plug, igniter plate, relief cock, etc.		Test by running oil around these and cranking.		Leak indicated by bubbles.
						Piston ring splits in line.
						Broken piston rings.		Crank case will be abnormally warm.
						Cracked walls or head.		Indicated by water in cylinder.
						Sticking valves.
						Insufficient space between valve stem and push rod.

COOLING. (Water.)		Radiator should heat evenly shortly after engine is started.		Radiator does not heat.		Clogged circulation system.		Empty tank.
								Clogged piping.
								Defective pump.
						Test by opening pet cocks.
				Radiator steams.		Failure of lubrication.		Indicated by groans from cylinders affected.		Supply should be just sufficient to produce faint whiff of blue smoke at exhaust.
						Defect in circulation.
						Too much running on retarded spark or on low speed.
						Slipping fan drive.

* It is taken for granted that the engine is capable of running properly, that the tanks are filled, and that the switch is correctly thrown.

[1] Return to makers for repair.