13. A general approach to troubleshooting

Any troubleshooting situation involves answering 3 basic questions: (1) Does the engine have compression? (2) Does it have spark? and (3) Is it getting fuel? If an engine has those 3 requirements met, it has to run! It might run poorly, depending on its condition, but that is a different matter.

COMPRESSION?
In a troubleshooting context, the easiest thing to do is to remove all 4 spark plugs and hold your thumb over each spark plug hole while your cranking the starter. If you can't hold the compression back with your thumb, the compression is at least OK. With experience, you can say that compression is poor, normal, or “pretty good”. Here are a few things to consider regarding compression checks:

a. To avoid getting shocked by the spark plug leads, remove the high tension lead from the center of the coil.

b. If you're by yourself, you can crank the engine from the engine compartment by shorting across the “S” terminal and the large terminal where the battery cable connects to the starter solenoid using a common screw driver.

c. Be sure and close the raw water thru-hull valve on the water intake so as not to flood the exhaust system during cranking and cause water to back up into the engine.

d. Zero compression on one or two nonadjacent cylinders usually means a stuck valve(s). Zero compression on 2 adjacent cylinders usually means a blown head gasket. Zero compression on all four cylinders can mean water has gotten into the inside of your exhaust manifold and has resulted in all four intake valves sticking open. The presence of adequate compression usually confirms the general integrity of the entire mechanical construction of the engine, even to include an open exhaust system.

IGNITION?
With all 4 plugs still removed, reconnect the coil lead to the coil. Hold the other end of the coil lead about 1/2” from the head or block and check for spark while having someone turn the engine over on the starter.

a. The spark may not be as strong as you'd like, and you can't tell (without further checks) how closely the timing is set to TDC. However, unless the distributor has become loose, it's not very likely that the timing has shifted enough to keep the engine from running.

b. If there is no spark at all, as in the first attempt to start in the spring, the most likely cause is a thin layer of corrosion over the points which prevents them from making contact and functioning as a switch.

c. If you have any other electrical apparatus connected to the + terminal of the coil (or even the - terminal as in the case of an electrical tachometer), these things all can fail in such a way as to interrupt proper functioning of the coil and should be temporarily removed while you're doing serious trouble shooting.

FUEL? We're not talking here about how correct the mixture is, but simply whether or not any fuel is getting to the combustion chambers. The easiest thing to look for is a damp appearance and fuel smell on the spark plugs. A second indication of fuel availability is to remove the flame arrestor and check for some presence of raw fuel in the intake throat of the carburetor. If you have been turning the engine over on the starter for some period of time (especially with the choke pulled) there should be some evidence of raw fuel in the carburetor intake.

NOTE: Some people assume that if there is raw fuel in the intake of the carburetor that the engine is flooded. Because of the updraft design of the carburetor, it is virtually impossible to flood the Atomic 4. In fact, even if there is fuel puddled in the throat of the carburetor, it may still be necessary to choke the engine for a good start. If compression, ignition, and fuel appear to be functional, the problem must be assumed to be intermittent. - Updated: November 4, 2003