Scary

[JimMc]

For many years diesel engines were shut down by mechanically closing off the fuel supply ( a diesel engine doesn't have an ignition circuit like a gas engine). The key, if you had one, was to access the starter and lighting circuits.

I remember the first diesel tractor I ran as a kid. I turned the key off and it just kept running. A local farmer had hired me to help him out and I didn't want to admit I didn't know how to shut it down so I left it running thru lunch. For a week, every night I would shut it down by thottling down to an idle and letting the chutch out to kill it. Finally one night, he saw me do this and came over and showed me the red fuel shutoff knob. I felt like an idiot, but he was OK about it.

Nowadays, most manufacturers use a fuel solenoid, and turning off the key shuts off the fuel.

This is why many tractors also use an accumulator to indicate engine hours. The tach is mechanical driven off the camshaft rather than electric. Electric indicates the number of hours the circuit has been energized, mechanical accumulates the number revolutions the engine has made regardless of speed.

 

[Bird]

Bob, JimMc has already answered the basic question, but I 'll try to expand on it a bit. On the gasoline engines we're all familiar with, an electric spark ignites the fuel in the cylinder, so when you turn off the key, you stop the electric current to the spark plugs and with no spark, the engine quits running. But diesels have no spark plugs; compression and heat ignites the fuel in the cylinder, so to kill the engine, you stop the fuel from going to the cylinders. Now most things now; cars, trucks, AND tractors have an electric solenoid that closes a valve to shut off the fuel flow (and my 1999 B2710 had such a solenoid), but prior to those solenoids, most (if not all) diesels had some kind of mechanical valve, even in fairly recent years. On my 1995 B7100, the throttle lever had a "detent" that felt a little similar to going into "float" with the joystick on the FEL. You pushed the throttle lever forward to give it more "gas" and you pulled it back to that detent to idle the engine. Then you pulled harder, all the way back, to kill the engine. And on the Oliver that I used so much baling hay, there was a knob on the dash (kinda remind some of us old folks of the old manual choke knob for gas powered cars, but bigger), pull that knob out and that shut off the fuel and killed the engine. Now, personally, I never had a problem killing the engine. The problem was that sometimes I hopped on a tractor and tried to start it and when it wouldn't start, then I'd remember to push that knob in on the Oliver or push the lever forward past that detent on the Kubota./w3tcompact/icons/frown.gif/w3tcompact/icons/laugh.gif

 

[larso1]

...and on my diesel tractor (Iseki w/ Isuzu motor), you shut off the air instead of the fuel. The pull handle closes a butterfly valve that shuts off the air supply to the combustion chamber, and it stops right now. There is a small shut-off cock at the fuel filter, but you would have to climb off the tractor to get to it. I thought they were all that way until I read the above posts. That's what I like about this site...I learn something new almost every time I visit.

Bill in CO

 

[Bird]

Yep, Bill, it takes both air and fuel for combustion so shutting off either will kill the engine. I think the fuel shut-off is much more common, but don't know for sure what the ratio might be.

 

[JimMc]

You know, Bird, it seems I also got in trouble for not pushing the shutoff knob back in immediately after killing the engine once. It seems it was a pet peeve of my Dad's to crank and crank with no fuel. Plus it was winter and the linkage froze, so even when he figured it out we couldn't start the tractor. Had to carry hay out to the feeder by hand, and man was it cold. The more I think about it the more trouble I remember getting into.

 

[Bird]

/w3tcompact/icons/laugh.gifI can understand that./w3tcompact/icons/laugh.gif I did try to get in the habit of pushing the knob back in after the engine died, but sometimes forgot to.

 

[DavesTractor]

My dad used to tell me to leave the knob pulled out. He said most thieves are stupid and won't be able to start the tractor!

 

[JimMc]

Several years ago, before the modern anti theft packages, I put a switch in the neutral safety switch circuit and another on the electric fuel pump circuit in my 1970 SE Charger as a theft deterrant. Just to really confuse people, I also reversed the OFF/ON labels on the switches. /w3tcompact/icons/laugh.gif

 

[kayssupply]

We did something like that to my Dad's motor home. We put a horn button on the dash, that had to be pushed and held or it wouldn't start. The trick was you also had to turn on a switch marked wipers or all that happened was the horn honked. The dash was so open you could have hot wired it in about two minutes otherwise.

 

[JimMc]

The down side of pushing the fuel shutoff back in is that if the tractor is left in gear on a hill and begins to roll, it will start and run off. Never happened to me, but I always worried about it. When the starter went out once, we relied on this. Push in the clutch, release the brake, let out the clutch, and away you go. Of course, that's assuming you remembered to park at the top of the hill.