atomic four problems

[coryh]

I have a Catalina 27 with an atomic four. For the last few months the engine has been dieing after 30 minutes. It starts back up after about 5 minutes. I pulled the coil and held it to the engine block and it seems to get spark.

I've recently installed a Moyer Marine fuel system kit with the Racor filter, the inline filter, electric fuel pump etc. I checked the fuel pickup line and removed the wire mesh at the end of it. I've removed the gas cap in case a vacuum was being created in the tank. One thing I've noticed is that the fuel system gets very pressurized. I installed an inline hand pump before the Racor and it fills with pressure to the point where you can't pump it by hand. Is this normal? Does anyone have any other things that I can try?

[tenders]

It seems to me that if your hand pump is installed between the filter and the tank (ie, upstream from the fuel pump and carb) that you should expect not to be able to pump fuel with it in any measurable way if everything downstream is functioning properly. You'd be trying to move it past the electric pump, then into the carb float chamber and around the needle valve...not ending up anywhere good. The fuel pump moves a gallon an hour that way, or less.

Your other symptoms sound like your coil has expired. Once an old coil gets hot I think what happens is that it doesn't create a sufficiently strong spark and the engine abruptly dies. Then, after it cools for a few minutes, it will work a while longer. This symptom is sometimes diagnosed as "vapor lock," which refers to the case in which gas next to a hot engine vaporizes in the fuel system before it gets to the carb, but this is virtually impossible in an A4. If it ever gets that hot something else will surely vaporize, ie you, long before the liquid fuel does.

[coryh]

Coil

What is the best coil to use?

[Don Moyer]

Any good quality 12 volt internally resisted oil filled coil; or epoxy if you anticipate a wetter than usual environment or a lot of vibration.

Don

[Don Moyer]

It is normal for the fuel supply system to become pressurized when using a rubber priming bulb.

The best time to diagnose your situation is during the 5 minutes that the engine will not start. I'm attaching a small guide to help you do that.

Pending the results of your using the guide, my first guess is that you may still be having some air working through your system. I'd remove the fuel line from the carburetor and pump up to a quart of fuel through the system using the priming bulb. Then pressurize the system again and check closely for any fuel drips anywhere in the system.

Don