June 23, 2018, 04:48:00 PM

Author Topic: Bus started then stopped running this morning ...wont start now  (Read 8245 times)

Offline Dlsnow

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Bus started then stopped running this morning ...wont start now
« on: September 15, 2012, 05:15:22 PM »
Drove bus just fine yesterday
parked last night
Started this morning just fine
Ran for 3 minutes or so...built up about 30psi
then it shutdown on its own
i checked to see if the shutdown solenoid or emergency flap were triggered (nope)
Tried starting again...it turns over fine just no ignition
Had less white smoke than normal while it was running

Read some posts saying to check the fuel strainer and filter

I cant find them
Where are the fuel filters on a mci7 8v71?

Also last night i wrestled a bike out if storage and jostled the generator diesel feed and return lines. 
We have necer run tge generator.  Maybe i sent some air into the lines.
1972 MCI7 8v71 converted - 1kw solar on roof

Offline lostagain

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Re: Bus started then stopped running this morning ...wont start now
« Reply #1 on: September 15, 2012, 06:03:00 PM »
Look at the switches in the engine compartment. The one that says front, off, rear start might be on off. That would have engaged the stop cylinder on the governor as soon as it reached 30 psi. The one next to it says engine on, off. Same thing: it controls the solenoid you mentioned, but as soon as you get enough air pressure, it pushes that engine stop lever to cut fuel off. That is more likely than air in the fuel line, or plugged up filters, which by the way, are mounted on the engine cradle rail on the right looking from the bumper.

JC
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1977 MC5C, 6V92/HT740

Offline lostagain

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Re: Bus started then stopped running this morning ...wont start now
« Reply #2 on: September 15, 2012, 06:17:19 PM »
If you did put air into the fuel lines, you need to prime the system now. There should be a pipe plug on top of each filter (primary and secondary). Fill both filters with a measuring cup and it should start. You might have to repeat one or twice.

An electric fuel pump in line between the tank and the primary filter makes priming real easy.

JC
JC
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1977 MC5C, 6V92/HT740

Offline Dlsnow

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Re: Bus started then stopped running this morning ...wont start now
« Reply #3 on: September 15, 2012, 06:24:20 PM »
I started it from the rear.  The run/off switch was at run and i observed the shutoff solenoid retracted (run position)
The filters to the right of the engine look like napa oil filters and are oily.
Are they the fuel filters?
1972 MCI7 8v71 converted - 1kw solar on roof

Offline lostagain

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Re: Bus started then stopped running this morning ...wont start now
« Reply #4 on: September 15, 2012, 06:35:42 PM »
Follow the fuel line coming out of the fire wall. It runs to the primary filter. Then to the fuel pump which is on the front of the engine. Then to the secondary filter, then to one head, then the other. Then the return line goes from one head to the fire wall and back to the tank.

The 2 filters closest to the bumper would be fuel, and the other one closer to the firewall would be oil for the engine. Previous owners might have changed things around, so don't take my word for this, look at how the lines come and go.

Do you have a maintenance manual and a parts manual for your bus? You really need them if you don't. A DD V71 series service manual for the engine is good to have too.

JC
JC
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1977 MC5C, 6V92/HT740

Offline Dlsnow

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Re: Bus started then stopped running this morning ...wont start now
« Reply #5 on: September 15, 2012, 06:49:12 PM »
Thanks a bunch.  I have the mci partsmanual and maintenance manual.  The assembly looks right but the actual filters pictured look different.  Ill lookup the napa number and see.
where can i find a good dd 8v71 manual?
Sorry for the basic quedtions...im newe ti buses.
1972 MCI7 8v71 converted - 1kw solar on roof

Offline Dlsnow

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Re: Bus started then stopped running this morning ...wont start now
« Reply #6 on: September 15, 2012, 08:49:55 PM »
Ok found them, they are napa 3118 and 3120  fuel fikters.  Now they are on there tight, cant get them off.

More elbow grease i suppose, any tips?
1972 MCI7 8v71 converted - 1kw solar on roof

Offline Stormcloud

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Re: Bus started then stopped running this morning ...wont start now
« Reply #7 on: September 15, 2012, 09:02:09 PM »
Strap wrench....also, fill the new filters with fuel before installing them.

Does it start and run with a small shot of ether?? Not a good practice, but it may narrow the possibilities...

Don't forget....a small shot only......and only 1.
Mark Morgan  
1972 MCI-7 'Papabus'
8v71N MT654 Automatic
 Brandon, Manitoba, Canada in summer
 somewhere around Yuma, Arizona in winter

Offline Dlsnow

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Re: Bus started then stopped running this morning ...wont start now
« Reply #8 on: September 15, 2012, 09:38:51 PM »
Shot of ether made no difference

Shutoff fuel input petcock
Got the secondary filter off and it was full / spillingover
still cant remove primary filter
1972 MCI7 8v71 converted - 1kw solar on roof

Offline Ed Hackenbruch

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Re: Bus started then stopped running this morning ...wont start now
« Reply #9 on: September 15, 2012, 10:01:22 PM »
When you put your filters back on, don't over tighten them......which might be why you are having trouble getting the primary off. Get a good filter wrench, the chain type is best.
1968 MCI 5A with 8V71 and Allison MT644 transmission.  Western USA

Offline bobofthenorth

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Re: Bus started then stopped running this morning ...wont start now
« Reply #10 on: September 15, 2012, 11:50:06 PM »
If the secondary is full then you don't need to worry about the primary. 
R.J.(Bob) Evans
Used to be 1981 Prevost 8-92, 10 spd
Currently busless (and not looking)
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What's behind you doesn't matter - Enzo Ferrari

Offline PP

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Re: Bus started then stopped running this morning ...wont start now
« Reply #11 on: September 15, 2012, 11:55:32 PM »
Ignore me, I'm following thread,  :)

Offline Lin

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Re: Bus started then stopped running this morning ...wont start now
« Reply #12 on: September 16, 2012, 01:21:42 AM »
If your saying that a shot of ether does not make any difference, it would seem to be an air problem rather than fuel.
You don't have to believe everything you think.

Offline Rick 74 MC-8

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Re: Bus started then stopped running this morning ...wont start now
« Reply #13 on: September 16, 2012, 01:24:50 AM »
If the genset lines are Tee d into the main fuel line its sucking air from those lines tha got ripped loose



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About 20 Miles West Of Chicago

Offline Dlsnow

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Re: Bus started then stopped running this morning ...wont start now
« Reply #14 on: September 16, 2012, 02:04:29 AM »
bobofthenorth - that is good to know - however, i dented the primary trying to remove it with a strap style wrench - so im putting the new one on

Lin - i wasnt sure if it would fire with ether only - but i would expect a good amount of white smoke if it was getting diesel and not air (am I right here?)

Rick - that seems to make the most sense - i am not sure if they are tee'd to the main (return or supply) - cant wait to trace those hoses (they go directly into that center channel [old walkway])

So I need to replace the primary filter  (and fill it with diesel before installing).
Do I need to prime the fuel system after this?  I have heard that sometimes the pump looses prime.
Should I isolate this issue of "losing prime" by removing the return line at the firewall and checking for fuel while starting?
1972 MCI7 8v71 converted - 1kw solar on roof