Bus Won't Start - Solved!

[ChuckMC8]

Here's my setup- A stop at Auto Zone (or similar) low pressure 12V fuel pump, Mine is 24V, because I had the pump, and then a stop at Home Depot(or again, similar store) just look at the photo and you can make an easy list. To operate elect pump, close the ball valve (else it just pumps fuel back to the tank!). I put the on/off switch in the rear remote box at the back door.

This setup is on an MC8, 2 year old photo. It made me cringe to see the grease on the bulkhead!

[Busted Knuckle]

Nice set up Chuck and almost just like my mobile set up ('cept I left mine mobile for service calls, and such! ) BK
We hav'n the " TN Fall Bus Bash" at Knuckle's, we gonna party at Knuckle's 

[NJT5047]

The best place for the primer pump is as close to the tank as possible with some kind of vavle to keep from pumping fuel back into the tank. Since this is a suction system it is easier on the small elect pump to be close to the fuel.

One reason for this location is that it will drive air out of the system if there is a leak somewhere and when the air is out it will pump fuel out at the same location and show you where the leak is.

If you have it near the filter and there is a leak between the filter and the tank it will just suck in more air.

While I agree that the tank end is preferable, an MCI isn't the easiest unit to get into the fuel line.
NJT installed a primer in the front.   Installing in the rear is way easier, and the presence of are in the line would be a dx negative...then one would have the opportunity to check backwards until the leak is resolved. 
Chuck's pix is exactly what I'd do had I not had an OEM primer installed.   The clear lines are a good idea too...wouldn't have thought of that touch. 
The pump could also be inserted just ahead of the primary filter. 
Best, JR

[El-Sonador]

I'm no expert, but if relating a problem I had on my MC-9 [8v71 may help...

I was in for routine fuel filters, the boys in the shop failed to keep my fuel lines and the new filters full and tried to re-start my bus... Obviously it would not re-start due to air in the system.

I made them stop trying to start it and insisted that they run a shop air line into my fuel tank and put the fuel tank under pressure while trying the re-start. The pressurized air in the tank forced the fuel through the empty fuel lines and fuel filters until it ran on its own. Took less than a minute.

I don't know if this would help your situation out or not, but I don't think it would hurt and it did work for me. Just be careful that you don't abuse your starter.

IF... you suspect algae in the fuel, the marine industry suffers from that a lot and they sell an additive to kill the algae and prevent it from forming. That wouldn't hurt to try that also...

That's about all the 2 cents I have on this one...

Sorry I couldn't be more helpful... Let us know how you make out...


Steve

[DavidInWilmNC]

Ok, here's an update.  I tried starting and it sounded like it might start... for a second.  I removed the primary fuel filter.  It was completely full of fuel.  I had a friend crank it with my hand under the exhaust pipe.  A puff of air came out, then very little.  It smells really bad - much worse than usual!  It's got this acrid, bitter smell that reminds me of a gasoline engine running way too rich when you cut it off (like old V8's that would 'diesel' when turned off).  It sounds kind of funny, too.  It reminds me of how my Honda sounded when the timing belt broke.  Of course, I'm not sure what an 8V-71 should sound like.  I didn't get a chance to check anything else, as it started raining. 

I looked for the em. shut down, but I don't know what it looks like.  I couldn't find it at all in either the parts or service manuals.  If anybody can point me in the direction as to what it looks like/ where it's located, I'd appreciate it.

I'm thinking I need to check the following

1) air intake for obstructions
2) fuel for flow, opening the return pipe would be the easiest way, a pressure gauge  on the 2nd filter would work too
3) check the em. shut down
4) check the blower for operation

I'll check those things, plus anything else anybody can suggest.  I just hope it's nothing serious!  Thanks, as always.

David

[DavidInWilmNC]

Come on, guys!  I know somebody has to have an idea of what's wrong.     I really need a shop to work on this... trying to work on a bus engine in the rains sucks!  Thanks.

David

[Ross]

Come on, guys!  I know somebody has to have an idea of what's wrong.     I really need a shop to work on this... trying to work on a bus engine in the rains sucks!  Thanks.

David

The nice thing about these old two strokes is if they have compression, fuel and air, they will run.  If it wont run, you must be missing one of these.  If it ran prior to a filter change, I'd bet on fuel.  If you haven't added a primer pump yet, that would be a logical next step.

[DavidInWilmNC]

The nice thing about these old two strokes is if they have compression, fuel and air, they will run.  If it wont run, you must be missing one of these.  If it ran prior to a filter change, I'd bet on fuel.  If you haven't added a primer pump yet, that would be a logical next step.

Hi Ross,
No filter changes here... not since last year anyway.  I just removed one to see if it had fuel, which it did.  Thanks!

David

[littlehouse]

hi david
maybe you should'nt over think things, you said the bus was running so something happend while it was sitting. like the bird nest
in the tail pipe. we were with family in Fl. when i let the grandkids in the bus, it was full of work stuff, sooo all they could do was
stand by the drivers seat and see how big it was. two days later it would'nt start, like yours alittle bit then nothing, i tryed everything
filter, tank, primer pump lines,then i pulled the blower and found abig plate down thight on the intake"emer. shut off". one of the kids had fliped the switch up front. i don't know if this helps at all but i wish you lots of lock.
ray with the littlehouse          i tryed to post earlyer but no luck so maybe it will post twice, if so sorry

[El-Sonador]

I looked for the em. shut down, but I don't know what it looks like.  I couldn't find it at all in either the parts or service manuals.  If anybody can point me in the direction as to what it looks like/ where it's located, I'd appreciate it.

IF... you are talking about the emergency air damper shut down, it is located on the top center of the engine. There is a lever there that you can manually trip to shut down the air supply going into the engine, in the event of a "run-away" There is also a switch on your dash to electrically trip this damper. But it must be re-set manually by re-opening this damper at the engine.

I have done this a few times, once to test the system, but that was several years ago. I carry a sawed off broom handle in the curb side engine compartment that I used to trip the air damper to manually shut it down. Kinda of scary sticking your face into a run-away engine... This is a good location to access this damper. I also had to do this one other time when my accelerator jammed open in the full throttle position. I hit the emergency kill switch but it didn't work, had to run back to the engine compartment to do the manual shut down.

I too looked for the longest time through all my manuals for you. but I could not find it in there either.

I hope someone here that is more familiar with this can chime in here on this.


I know how frustrating this must be for you...


Steve

[gus]

David,

Fuel from a diesel exhaust that isn't burned really stinks. This is very common on DDs when first started in cold weather. The Cat 3208 stinks like this even in warm weather when it first starts.

The emergency shut off valve is actually a metal flapper that covers the intake to the engine blower. There should be a toggle switch on your dash to operate this valve. It blocks all air so the engine cannot start.

671s have this valve but somewhere I think I read that 8V71s don't all have this, I don't know for sure.

I wasn't talking about this valve. The one I mentioned in my first post is for use by mechanics working at the rear so they don't have to go forward to stop the engine. There is also a start switch on the same panel at the rear. MCIs may not have these switches.

JR,

Fortunately the 4104/06s have a top hinged door over the fuel tank that looks like a baggage door, it is very easy to access.

[ceieio]

OK - so I did a little flash photography tonight... I am pointing to the emergency stop on the 8V71 in my MCI.  You will notice the catch mechanism that holds the shaft from rotating at the end of my finger.  (You may also notice the WD40 I sprayed all over last weekend.   Be polite and pretend I just cleaned everything up back there, which I will, real soon now). 

You can make out the shut off shaft just above the hose in the photo, running back under the lid with MCI cast into it.  There is a "handle" that is pointing off at about the 2 o'clock position (arrow).   This photo shows the emergency shutoff in the normal "run" position.  If the emergency stop is tripped, the "handle" would be rotated counter clockwise from its current position, and the notch in the shaft would be disengaged from the catch.

To reset, grab the handle and rotate it clockwise until the catch seats in the notch.

I hope the picture does better than my words!

Best Regards,
Craig - MC7 Oregon

[ceieio]

I suppose I should have mentioned that the shutoff is right at the back end of the engine (as mounted in a bus).  Just look past the blower drive belt and you should see the shutoff mechanism back there just a few inches behind of the fan-drive belt, slightly to the curbside of the engine centerline.

Craig - MC7 Oregon

[NCbob]

I didn't review all the posts but David, did you try running the engine on an alternate source of fuel...like a 5 gallon can of fresh feul from the local Station?  It'll run fine on Kerosene if that's all you can find locally.

NCbob 

[DavidInWilmNC]

Ok, so now I feel like an idiot.  NCbob, littlehouse, El Soñador, gusc, and ceieio were right on.  It was the emergency shut off.  I'm not sure how or when it tripped, as I always keep the master switch turned off.  The funny thing is, it's not mentioned in any parts or service manuals and is different from the pic Craig posted, but I imagine that there were some changes over the years from the MC-7's to the -8's.  That pic is what got me going... thanks Craig!  In the process, I removed my air cleaner - very nasty, and am doing a few other things.  This problem had me stumped, but now I know that the shut off works and know how to reset the damned thing!  I'll also be installing a fuel primer as so many have suggested.  Thanks ChuckMC8 for the pics.  That's probably how I'll install mine.  Anyway, I appreciate everybody's help, input, and suggestions.

David