Posted: February 16 2009 at 12:25 | IP Logged

My 1953 Chris MLB engine with a zenith updraft runs great for about one hour then stops running. The motor will start than die as if starving for fuel- this is not the case. Filters and carb are clean. The motor will start and again run fine after about 1/2hr. Can the cause be icing? We live in Georgia and have humidity.

Thanks for any help on this subject.

Posted: February 17 2009 at 20:36 | IP Logged

Mr T-

The question of whether your fuel system is icing depends on outside temprature. Georgia with humidity suggests icing will not happen. Like refrigeration, the process of atomizing gasoline in a carburator does bring the resultent gasoline mist down in temprature some, but Gasoline's freezing point is well below that of water.

Perhaps starting with basics: Fuel problems usually means the engine misses, sputters, runs rough, load down but doesn't quit immeadiatly.

Ignition problems usually shut down the engine flat...nothing at all OR...sudden or short sharp cuts in and out like a connection going intermintent.

Can you discribe in more detail what happens when it stops running ? Gradual or instant? Engine Temp ok? oil pressure ok?  It sounds like the engine starts right up after letting it set a spell but runs for a shorter period of time next you fire it up...1/2 hr?

You might inspect the spark plugs for an indication. Remove all plugs, keep in them in order.  Inspect electrodes color - should be brownish, wether it's wet with oil?, wet with fuel?

Hmm...

further symptoms may tell the tale.

Fair winds, Diver