New Massey 255.

[Floopy]

The oil pressure switch is simple. The oil pressure closes the contacts to complete the electrical circuit. Think the oil pressure is you flipping a toggle switch lever to close switch contacts and complete a circuit. Shut the engine off, oil pressure drops and the switch opens shutting the gauge off.

It made no sense to me after initially getting the hood off. Then after seeing the comments here and a little more research it made sense.

I see the gas isn't set up this way. Why are diesels set up this way? If the contacts on the oil sensor don't work, it seems like it would be cheaper and easier to just change the key switch to a gas one with 3 posts and have a hot for the gauges on the key. It would let me check the gas and such as soon as I click the key on without pressure.

 

[Dieseltech]

Gas has the OFF/ON/START switch. The diesels used the oil pressure switch because the start switch was two positions, OFF/START. You DON'T have to remember to turn the switch off after shutting the engine down like some other make diesel tractors. My story as an OLD MF mechanic.

 

[Jim.ME]

Gas has the OFF/ON/START switch. The diesels used the oil pressure switch because the start switch was two positions, OFF/START. You DON'T have to remember to turn the switch off after shutting the engine down like some other make diesel tractors. My story as an OLD MF mechanic.

Yup, no "I forgot to turn the switch off", as I have seen on tractors having a mechanical mechanical fuel shut off and an Off-On-Start key switch.

 

[ford4wd08]

I went with the 3 position switch from a gas model on my diesel when I added the fuel gauge back in with a new sending unit.

All my other tractors are setup with a 3 position switch, so it is habit to turn it off after I kill the diesel engine.

 

[miangus]

John Deere built a lot of tractors where you could shut off the diesel but leave the key on. I have a ford 1510 that's that way too. Those 24-volt Deere's were hard on batteries they didn't need a system to run then down. My 65s have a three-position switch; Crank, Themo-Start No-Crank and Thero-Start Crank.

 

[Floopy]

I guess I forgot it has a fuel shut off to turn it off. It makes sense why it doesn't have a key off with that in mind. Probably best to just fix it right.

 

[Bill in Colo]

You will love your 255. I have one I bought from my FIL's estate ,(new in 78 only new tractor he owned) had a F10D farmhand loader he used for 20 years, he put up loose hay for years and large rounds. I took the load off to use for a rake tractor.