8V71 Shut Down Valve Question?

[Dreamscape]

When I turn off the ignition switch the engine will not shut down.

The solenoid works, the valve rod is extended. It is just no extended far enough to meet up with the linkage arm.

How do you adjust it?

I assume the valve is shut down the air supply to the blower. Am I on the right track? I just don't want to screw something up regarding the air supply under normal running condition.

Does anyone have a photo of that area showing the high idle vavle also. That also works, but does not touch the linkage.

Paul

Dreamscape

[gumpy]

Here's some shots of the stop engine and fast idle cylinders on an 8V71. Before and after replacement.

Check the bolts to make sure they are tight. I've see where one bolt falls out, and the assembly rotates where it won't activate
the shutdown lever.

[buswarrior]

Hello Paul.

The regular shut down stops the motor by shutting off the fuel.

Diesels are controlled by the fuel injected, gasoline engines are controlled by the amount of air allowed into its throat.

I echo the comments about checking the fasteners on that little air cylinder. The one you are after is the one closest to us in the excellent pictures posted by gumpy.

You may pull on that hooked lever with your finger to shut off the motor. It needs a strong pull, and has to be held until the motor stops, or it will pick up and keep running. Keep your finger out from between where the air cylinder pokes out. If it is activated with your finger in there, you'll be able to do party tricks you don't want to be able to do....

Go easy on the screws, they can be easily stripped. Adding a small star washer might help, if there isn't one.

happy coaching!
buswarrior

[Dreamscape]

Great photos, Thanks,

Everything is secured and tight.

I can move the lever that the shut down valve pushes on, the engine does shut down. Can I adjust the lever by rotating it closer to the valve so when it is activated it pushes the lever farther?

Paul

[gumpy]

Possibly.

The lever should be up against the cylinder rod when in the retracted position. I'm not sure if the shaft is keyed, but I think it's just knurled, so you might be able to loosen the lever on the shaft, and rotate it till it touches the rod and tighten it on the shaft again.

craig

[Dreamscape]

I think I will wait to tackle this when I get the manuals for the DD 8v71 from Chuck. They may have a procedure listed.

Thanks for the suggestions.

Paul

[Stan]

I posted an answer this morning but it seems to have ended up in www never-never land.

The shut down cylinder and the high idle cylinder will not work until pressure is sufficiently high in the dry air tank.

Both levers on the top of the governor can be rotated on the shaft by losening off the clamp bolt.

BTW: The cylinder that pushes on the throttle lever is not the high idle but is the safety that prevents the throttle from being used when the park brake is applied.

[gumpy]

BTW: The cylinder that pushes on the throttle lever is not the high idle but is the safety that prevents the throttle from being used when the park brake is applied.

Uh, no it's not.

If it were, you wouldn't be able to rev up your engine using the throttle when you start up the bus or are sitting there idling, and I'm pretty sure I can do that.

The high idle cylinder is part of the high idle mechanism (hence the name). It prevents the throttle from being overdriven by the high idle. The parking brake must be applied for high idle to engage, and one result is that you can't use the throttle when the high idle is engaged. Maybe you're confusing that with parking brake.

[Stan]

Craig: You are probably right. The high idle and the park brake are interconnected and you can't have high idle unless the park brake is applied and you can't open the throttle when on high idle so it makes sinse that the primary control is the high idle.

You have just been working on this so you are familliar with it. If the lever I referred to is not the throtle stop, what is it and what is for for?

[gumpy]

Well, I don't fully understand how the governor works yet and the high idle control, but I believe you were correct in that the lever you referred to is the throttle and the high idle stop cylinder pushes on it and prevents the throttle from being pushed too far by the high idle cilinder, which is a separate cylinder on the side of the governor.

This is part of the regulation of RPMs during high and low idle. There's a buffer screw in there somewhere, too, whose function I'm not sure of yet, either. Again, I don't fully understand how the two speed governor works. There's an adjustment sequence in the manual, but it was not at all clear to me. I'm hoping to get a better explaination from my mechanic the next time I'm down there. What I have heard, though, is that adjustment is touchy, and can lead to a runaway engine if not done properly. I think that's where the high idle stop cylinder comes into the picture.

And you are correct in that they are interlocked. The parking brake must be on, the foot brake released, and the transmission in neutral fo the high idle to engage, and the stop cylinder does indeed prevent the throttle from being used when high idle is engaged.

Maybe one of the DD mechanics on the board will post a High Idle for Dummies version for us all.

[Stan]

Thanks Craig: My bad for saying the park brake instead of the high idle causes  the throttle stop to engage. My understanding is the high idle cylinder is preset internally and is not normally adjusted.

Before doing any project, I assess the skills required and the special tools needed.. My assessment on DD governor adjustment is that it is better to have an experienced DD 2 stroke mechanic do it.

[gumpy]

My assessment on DD governor adjustment is that it is better to have an experienced DD 2 stroke mechanic do it.

Until I learn more about it, that's my assessment, also.