Decompression lever

Dunggatherer · Post by **Dunggatherer** » Thu Jul 17, 2008 9:39 pm

Good day Gentlemen,

I hope someone can explain something to me.
Currently i am restoring a Ferrari tractor.
The only way to start it seems to be by lifting the decompression lever,spinning the engine with the starter motor,and then let go of the lever,so the engine starts.Works fine.
There's no way the starter motor will spin the engine without decompression.
Even though it's rebuilt,got new wires,even a new ground wire straight to the battery.
So i started a search.
It seems you are not supposed to start a Major this way,as the valvelifters can jump off their seats or something like that.
Now last week i read a story about a certain type of crawler (Cat D60?) which must be started this way.With a pony engine by the way.
So this got me curious...
Can someone shine a light on this dark matter?

Greetings from the Netherlands.
Rob.

Post by **Brian** » Thu Jul 17, 2008 10:09 pm

Rob,

A lot of tractors used a decompressor to start as you describe. The John Deere has taps to release compression until the engine starts, Cats use it to get the engine swinging, Field Marshals did the same. A variety of small diesels in cement mixers, dumpers etc. all had them for hand starting.

But all these engines were designed to start this way, the Major was not. It was only supposed to be used to turn the engine slowly to break oil lock in cold weather.

Dunggatherer · Post by **Dunggatherer** » Thu Jul 17, 2008 10:14 pm

Alrighty then,thanks a lot for this fast answer!

And again i learned something new.
Till now i thought it was meant to allow one to set the timing and stuff.
Ummm what's oil lock?

Post by **Brian** » Thu Jul 17, 2008 10:26 pm

When the oil is so cold and stiff that the starter would have difficulty in breaking the seal it forms. If you turn the engine by hand it will free off and so not overload the starter.