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Author Topic: Engine shut off while idling... now wont start  (Read 872 times)
topfrog007
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« on: April 22, 2012, 08:32:11 PM »

Guys,

86 MCI 102A3. 6V92TA

I had the bus Idling on our driveway for a few minutes today when the engine shut off, sounded like it ran out of fuel. I've done this a few times over the past few months to let the air build up and check some various fixes/functionality. Before it finished airing up the engine slowly died, it would not restart, it was turning over but never firing.

My first thought was that it sounded like it ran out of fuel, our driveway is a fairly steep incline and the bus is parked facing down the incline (engine at the highest point). The fuel gauge is about 1/3 full and I estimate it should have at least 30 gallons in there.

Is it possible the fuel got below a certain point for the fuel pump to suck it up because of the incline? Doesn't seem likely but who knows... Other ideas?

Thanks a bunch!
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Preston - Dothan Alabama - 1986 MCI 102A3
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« Reply #1 on: April 22, 2012, 09:20:05 PM »

Yes it could have run out of fuel.
But it could also be other things too!
The most likely one is the rear engine stop switch.
Sounds to me like it built up enough air and shut down.
Have you tried starting it after the air bled off?
Grin  BK  Grin
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Busted Knuckle aka Bryce Gaston
KY Lakeside Travel's Busted Knuckle Garage
Huntingdon, TN 12 minutes N of I-40 @ exit 108
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Grin Keep SMILING it makes people wonder what yer up to! Grin (at least thats what momma always told me! Grin)
Dave5Cs
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1979 MCI MC5Cs 6V-71 HT-740 Allison, Roseville, CA




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« Reply #2 on: April 22, 2012, 09:56:12 PM »

how old is your fuel, did you put conditioner in it over the winter.
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RJ
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« Reply #3 on: April 22, 2012, 10:09:50 PM »

Frog -

Only 1/3rd showing on gauge (notoriously innaccurate) plus parked on a slope = Go buy about 20 > 40 gallons of fuel, and get out your priming pump.

FWIW & HTH. . .

 Wink
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RJ Long
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« Reply #4 on: April 23, 2012, 03:30:48 AM »

I chased the EXACT same thing for hours before I realized it was the solenoid for the shut off lever on my 8V71. I felt silly but hey, I got it fixed.
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Scott Bennett
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« Reply #5 on: April 23, 2012, 04:32:09 AM »

Ditto on the engine stop shutoff. Don't move the coach (oh wait, you can't haha) and bleed off the air and then try to start again. Or you could manually pull the lever back into "start" position. I honestly think it's that...but could be fuel level too..
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Scott & Heather
1984 MCI9 6V92-turbo with 9 inch roof raise & conversion in progress.
http://www.scottmichaelbennett.com/p/our-bus.html
˙ǝɯoɔlǝʍ suoıʇɐuop ˙snq ʍǝu ɐ pǝǝu ʎlqɐqoɹd ll,ǝʍ 'sıɥʇ pɐǝɹ uɐɔ noʎ ɟı
bevans6
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« Reply #6 on: April 23, 2012, 05:20:31 AM »

And while we are speaking of engine shut offs - there are often two of them.  The normal engine stop lever on the top of the governor, activated by an air cylinder controlled by a Skinner valve, and the emergency stop flap valve on top of the air intake manifold, activated by a electric solenoid and the emergency stop switches.  That one is known to randomly apply itself and have to be manually reset, that happened to me twice.  Sadly, it took just as long to figure out the second time as the first...  Symptom is the engine cranks and lots of white smoke comes out.

Reading your original post again, engine starting and running fine and slowly dying as the air builds up is classic engine stop lever problem.  What happens is the air supply to the Skinner valve that controls the engine stop air cylinder is fed from the accessory system, which is after the Pressure Protection valve.  The engine must run long enough to build up 65 psi of pressure before the PPV opens, then must run long enough to build up pressure in the accessory system to move the engine stop air cylinder and the effect is the engine stop lever is very slowly activated and the engine just slowly dies.

What smoke appears as you crank is a good clue.  If lots of white smoke pours out the exhaust, that means there is fuel and no air.  If no smoke at all comes out, that means there is no fuel.  That can be either no fuel (duh!   Grin), or the engine stop lever activated.

Brian
« Last Edit: April 23, 2012, 05:22:25 AM by bevans6 » Logged

1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
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« Reply #7 on: April 23, 2012, 05:53:38 AM »

Brian while you are correct about both shut offs on the 71 series. The 92 series doesn't have the air flapper. (OK let me be more specific, none of the ones I have ever worked on did!)

But still good info to share with those who don't know about them.
Grin  BK  Grin
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Busted Knuckle aka Bryce Gaston
KY Lakeside Travel's Busted Knuckle Garage
Huntingdon, TN 12 minutes N of I-40 @ exit 108
www.kylakesidetravel.net

Grin Keep SMILING it makes people wonder what yer up to! Grin (at least thats what momma always told me! Grin)
Scott Bennett
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« Reply #8 on: April 23, 2012, 06:05:26 AM »

my 92 series does not have the emergency flap either. And as if to remind me every day, it says so on a bid red tag on my dash. Should I lose sleep over that?
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Scott & Heather
1984 MCI9 6V92-turbo with 9 inch roof raise & conversion in progress.
http://www.scottmichaelbennett.com/p/our-bus.html
˙ǝɯoɔlǝʍ suoıʇɐuop ˙snq ʍǝu ɐ pǝǝu ʎlqɐqoɹd ll,ǝʍ 'sıɥʇ pɐǝɹ uɐɔ noʎ ɟı
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« Reply #9 on: April 23, 2012, 06:11:52 AM »

my 92 series does not have the emergency flap either. And as if to remind me every day, it says so on a bid red tag on my dash. Should I lose sleep over that?

Only if you have absolutely nothing else in the world to worry about!
Grin  BK  Grin
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Busted Knuckle aka Bryce Gaston
KY Lakeside Travel's Busted Knuckle Garage
Huntingdon, TN 12 minutes N of I-40 @ exit 108
www.kylakesidetravel.net

Grin Keep SMILING it makes people wonder what yer up to! Grin (at least thats what momma always told me! Grin)
Scott Bennett
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« Reply #10 on: April 23, 2012, 06:13:44 AM »

thanks Bryce  Smiley good. in that case, I'll worry about topfrog's coach not running  Wink let us know what your result is!
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Scott & Heather
1984 MCI9 6V92-turbo with 9 inch roof raise & conversion in progress.
http://www.scottmichaelbennett.com/p/our-bus.html
˙ǝɯoɔlǝʍ suoıʇɐuop ˙snq ʍǝu ɐ pǝǝu ʎlqɐqoɹd ll,ǝʍ 'sıɥʇ pɐǝɹ uɐɔ noʎ ɟı
bevans6
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« Reply #11 on: April 23, 2012, 06:29:48 AM »

Sorry about the air flap flap - I had in my mind that this was an 8V71.  DD went to spring loaded injector control levers and did away with the emergency flap.   The spring loaded levers allow the injectors to go to no-fuel if one injector sticks open.

Brian
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1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
Spicer 8844 4 speed Zen meditation device
Vintage race cars -
1978 Lola T440 Formula Ford
1972 NTM MK-4 B/SR
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