Whats is this and how do you use it?

Snap On MT 460

Cylinder Shorting Expanded Scale Tachometer

What is this used for and how do you use it.

This dude who broke into my parent's house and my brother tracked him down. After he beat the **** out of him he cleaned out his truck.

He found this diagnostic type tool along with a bunch of other Snap On stuff. But that is another story.

Anyway I was just wondering what this was used for.

 

I'm not real sure what you have there, but from its name it sounds like it is for performing cylinder drop tests.

Lets say you have a sick motor that has a miss. If you short out the ignition for each cylinder one at a time the rpm's will drop somewhat, until you short out the dead cylinder, in which case the rpm's won't drop at all. You just found the dead cylinder and now you can go on and diagnose the problem with that cylinder.

Now... you can do this manually by pulling spark plug wires one at a time while the motor is running and shock the holy bejesus out of yourself ( which may be the reason many mechanics twitch) or use something like you have there. Newer cars with fuel injection are much easier... hook up your scanner and turn off the injector to each cylinder one at a time, which is the recommended way to do it. Keep in mind that if you kill the ignition to a cylinder on a newer car that the injector is pumping raw gas into that cylinder that never gets burned and eventually finds its way down to the cat, which will soon turn blue hot or even explode. Customers love that while they watch you work...

 

Shouldnt your brother be trying to find out if all those snap on tools had been stolen from someone else.

 

You can see one on that auction site.---
http://cgi.ebay.com/SNAP-ON-MT-460-...0QQihZ013QQcategoryZ14932QQrdZ1QQcmdZViewItem

 

You use it to kill one cylinder at a time when the engine is running. IT has a tach to measure rpm drop when killing each cylinder. If a cylinder is weak the rpm drop will be less for that one or if a cylinder is missing there will be no drop in rpm for that one.

 

Not trying to justify what Gabes bro did, but we do things differently in the Valley....

 

Thanks guys.

Hey Rey, You got that right! That guy got what was coming to him. This crackhead broke into a house belonging to two elderly people (my parents) in the middle of the day.

Besides my brother is not much of an investigator.