Engine sputters and quits

[Unregistered]

The engine has new batteries, good fuel, properly maintained, new plugs etc, and new carb, fuel filter, water separator. It will start up and run smooth for about 15 minutes. When it reaches operating temp, it sputters and quits, or just barely runs. What could this be? When cool it runs well again. Oil pressure is about 25 lbs.

[Don Moyer]

The first step is to determine if the engine is stopping from lack of fuel or lack of ignition. Fuel-related shutdowns are somewhat "softer" in nature than ignition related shutdowns. Ignition related shutdowns are "sharper", sometimes stopping as though someone accidentally turned off the ignition switch, other times cutting in and out very sharply.

It's also important to review the recent history of the engine. Since the engine last ran OK, was anything done to the engine? If so, review that work.

If the engine doesn't start right back up, this is the best time to determine whether the problem is ignition or fuel:

Close raw water through-hull as soon as it's determined that the engine is not starting within the normal time.

2) FUEL: Remove the flame arrestor and check for the presence of raw fuel. If the choke is closed completely, there should be raw fuel puddled in the bottom of the intake throat within 15 to 20 seconds of cranking (3 or 4 five-second attempts). If the carburetor intake throat is "bone dry" after this amount of cranking, the reason for the non-starting is either a problem in the fuel supply which prevents fuel from getting to the carburetor or some problem within the carburetor that prevents the fuel from getting through the carburetor (most likely a blocked main jet).

3) Ignition: Remove the secondary lead from the center of the distributor cap and hold it approximately 1/4" from the cylinder head while someone cranks the starter. You should see a good arc between the end of the coil lead and the head that can be stretched to 1/2" or even 3/4". If you see no spark, the reason for non-starting is clearly within the ignition system, most likely a breakdown within the primary ignition circuit.

This quick check of the ignition system does not rule out timing issues. While the Atomic 4 has virtually no history of slipping out of time once the timing has been properly set, if the non-starting follows work that was accomplished on the ignition system, the timing should be rechecked.

Regards,

Don