Why a Decompression / Detiming Pull Knob

[Stubbyie]

Dear Fellow Orange-Addicted Owners:

A question...

One Kubota ('95 L35) has BOTH a key switch (that works) AND a knob to pull to kill the engine (also works).

Second Kubota ('05 L3130) has only a key switch.

Owner's Manual for the L35 says to pull the knob if key switch fails and then call dealer for service.

Is the key switch expected to fail?

Does anyone know the thinking behind having the pull-knob in addition to the key switch on one machine but not both? What changed in the years between the two?

 

[stuart]

I may be going over obvious things here.
To stop a diesel, you can cut off the fuel supply, which is done by the fuel solenoid (key switch), load it down until it stalls, or prevent combustion, which is what the decompression lever (pull knob) does.
The decompression lever is very useful when you have to bleed the fuel lines, like after changing fuel filters or running out of fuel. Cranks a lot faster and is way easier on the battery. I can't see being without it.
There are posts here abut the fuel solenoid getting stuck, open or closed.
I mention the stalling because my unit does not have the fuel solenoid, and the idle linkage is bent, so the only way to stop it is either the decompression lever (not recommended) or idle it right down then put some load on the hydraulic pump.

 

[birddogger]

Plus another reason for a decompression lever; the B7200 and a Yanmar that I use have a decomp lever, neither will start when hot, the starter doesn't have the oompah. So pull the compression release let her spin up and release the lever, vrooOOM. Don't know why they didn't just beef up the battery and starter, but both these units they knew you needed it and it's there. The NH's I use don't have them but the one has a battery the size of a kiddie wading pool.

 

[E/S]

Decompression lever also helps with cold starts.

E/S

 

[Ach]

Spinning the engine with the decomp pulled also allows the oil pump to get oil into the crankcase before ignition, decreasing cold start wear.