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Author Topic: Two strange behavior mysteries  (Read 473 times)
wagwar
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« on: September 15, 2012, 04:12:51 PM »

I've noticed a peculiar behavior on my MC9 w/ 6V92T. I often use a small air compressor or shop compressor to air up the bus - so that I don't have to run the engine so long on idle/fast idle. When I do that I always have to start the engine twice?  The engine always fires off right away, very little cranking or smoke. However, as soon as it starts and I release the start button, the engine dies. The second time it continues to run. If I start the engine first and let the engine air itself up, it doesn't require the second start.

I know it is the shutoff on top of the governor that is shutting it down, I just don't understand why it is doing that?

The last time I drove the bus I noticed that if I am using the jakes and I release the fuel pedal to slow down, I see a very short flicker of the tell tale lights. I did a little experimenting and found that if I hold the pedal just slightly off idle, I can get the tell tales to flicker. If I turn the jakes off they don't flicker.
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bevans6
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« Reply #1 on: September 15, 2012, 04:37:36 PM »

What are the tell-tale lights?

I have no idea about the first thing, sorry.  Got me stumped.  I do that same routine all the time.  Where are you adding air?  Does the shut-down air cylinder move?

Brian
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1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
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« Reply #2 on: September 15, 2012, 06:05:14 PM »

its the safety shutdown. its not seeing any oil pressure on the first button press. mine does the same thing. had me stumped at first until I realized it only started doing that after I replaced a leaking oil sensor.
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There are three kinds of people in this world....those that make things happen, those that watch things happen, and those that just wonder what the heck is happening. Which one are you?

1977 MCI Crusader MC-8
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Rick 74 MC-8
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« Reply #3 on: September 15, 2012, 06:19:27 PM »

That's right its the safety shutting down for lack of oil psi. If you still have the fuel psi sensor on the fuel filters you can hold down the starter button for a few seconds longer and it will stay running. As soon as it gets fuel psi the starter will disengage even with the starter button pressed. I still start mine twice I don't trust it. But that's how it is was designed to work




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luvrbus
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« Reply #4 on: September 15, 2012, 06:34:10 PM »

He shouldn't have a flicker when the Jakes are on probably someone picked up a hot lead on the dash somewhere instead of the rear panel
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