PA28 question

[Night Rider]

Hi all,

Just a quickie to ponder.

The Lycoming 0-320 engine on the PA28 Cherokee 140 has a conventional enough priming system, but is there any special reason why the primer only primes 3 of the 4 cylinders?

Many thanks.

[GoneWest]

Yep - if you overdo it, and flood the engine - you still have a chance of starting normally with the "dry" one.

[Oktas8]

GoneWest's explanation sounds wrong to me - flooded start procedure involves purging all the cylinders, and you certainly can't start a four cylinder engine with only one firing!

I always thought it was because only three cylinders needed to be primed - ie three out of four primed is enough to crank the engine over several times.

I'm only guessing though.

[Steamhead]

The fourth cylinder is used for connection of manifold pressure
gauge on those engines with constant speed propellers
usually #4 cylinder ( Stb'd aft cylinder)

Regards