Engine won’t shut off

treeplanter · September 30, 2021, 03:56:49 PM

Started my bus(8V-71)after sitting for two years, was idling a little high turned ignition to off engine kept running, got up to 30lbs air pressure before it ran out of air the emergency shut down failed to engage I blocked the intake, any help appreciated .

richard5933 · September 30, 2021, 04:29:48 PM

If you have a pneumatic control on the shut down system, flipping the switch up front won't do anything till you have adequate air in the tanks.

dtcerrato · September 30, 2021, 04:33:22 PM

Our 671 has pneumatic skinner valve. controll & can't be shutdown w/o air at least 60 to 65 psi as it is fed with the aux. air system.

luvrbus · September 30, 2021, 04:43:03 PM

If it was idling higher than normal a injector is stuck you probably have the 2 screw fuel control tubes and with a stuck injector they won't shut down with the air shut down

treeplanter · September 30, 2021, 04:58:02 PM

Ok really appreciate everyone's input, it could be it only reached 30lbs before it starved of air? It's air controlled throttle, the idle was high but not crazy high, I'm trying not to be ignorant of the governed system reading my 8v71 manual now.

dtcerrato · September 30, 2021, 05:04:55 PM

Da book is your friend...

richard5933 · September 30, 2021, 06:15:43 PM

Quote from: treeplanter on September 30, 2021, 04:58:02 PM
Ok really appreciate everyone's input, it could be it only reached 30lbs before it starved of air? It's air controlled throttle, the idle was high but not crazy high, I'm trying not to be ignorant of the governed system reading my 8v71 manual now.

Not sure what you mean by 'starved of air'??

The throttle on these engines doesn't open the air flow to the engine, but rather it opens the fuel flow to them. The air pressure on the gauge doesn't have anything to do with the engine's performance, at least not how I read your description.

Can you explain more about what you mean by 'starved of air'?

luvrbus · September 30, 2021, 06:38:14 PM

He can start the engine and push the stop by hand without any air pressure just keep your finger out of between the cylinder and the lever it hurts when the air pressure is high enough and it engages,the idle speed does not change with or without air pressure

treeplanter · October 01, 2021, 12:23:01 AM

Richard 5933
By starved in meant I blocked the intake until it stopped running, I see the jake break switch was on, wondering if that would increase idle speed? So I'm thinking not enough air pressure was built up to use the ignition key for normal shut off, will look at the rack for stuck injectors, I may have freaked out when the switch would not shut her down.

richard5933 · October 01, 2021, 03:26:54 AM

If the only problem was that the switch on the dash wouldn't shut things off due to inadequate air, then you don't have a problem.

Like Luvrbus said, in these situations you can walk to the engine and rotate the shut-down lever on the governor by hand until it shuts off the engine.

You should also spend some time getting the flapper in the intake to function correctly. It may not stop a full-bore runaway, but it will certainly stop an idling engine.

Jake brake switch should not affect idle at all unless something is wrong, and I've never heard of one making the idle go up.