HELP, Phil Lyons stuck on the road

[Stan]

Take the wire off the low oil sender and high water temperature sender and wrap tape around the end of the wire. You will be closely watching your gauges anyway when you have a problem.  If this solves the problem, you know that you have a faulty sender or a wire that is touching ground.

Another likely souce of problem is the shut down solenoid that operates the air cylinder on top of the governor. It has to have voltage at all times to keep the engine running. There are a lot of wires, terminals, diodes, relays etc involved in this circuit but you can connect 24 volts directly to the solenoid for a test run. You will have to remove the 24 volts to shut down the engine. If this solves the problem, you will have to go through the entire shut down circuit to locate the intermiitent.  In some coaches, careless washing over the years has caused a lot of corrosion in the rear terminal box. The wiggle test suggested by Dallas is good because it is not uncommon to have a wire broken inside a harness without any obvious damage.

[NJT 5573]

phil,If i remember right my old coach with an 8V71 was electric over air on the shutdown. Can't remember weather to pull the electrical wire and let it hang loose to come home or to just shut the air off to the switch. I'm sure that turning the air off to the switch will work though if you can't turn it off with the switch until you have air pressure. 

[Hartley]

Phil,

Pull the covers off the defroster area and bleed the air out of the defroster circuit at the top of the coils. I wonder if that was done after the hoses were all changed?

You heating system could be pushing air bubbles from the defroster and back into the engine since both are higher than the lines that feed the system.

Just a thought.... Hmmmmm....

[NJT5047]

Phil, do you have a "shutdown" device on the coach?  What Stan suggests may disable the unit, but some MUIs had a complicated system that monitored several parameters and would shut the engine down if any were outside normal limits. 
I'd disable such a device and install alarmastats.  At least you'd have the option of getting off the railroad tracks. 
Seems like "Robertshaw" made these things....is your coach an ex NJT or some other transit?  NJTs had an MUI shutdown on them. 
Stan can advise, but it may be possible to lock the shutdown cylinder in the "Run" position so as to disable the shutdown module? 
Craig (Gumpydog) has some history with an MUI  shutdown system that was acting up. 
As Dallas sez, be very careful taking intermittant problems to a shop.  You will pay for the time they spend looking for your problem....fixed or otherwise. 
IMHO air in the coolant system would not cause what you describe...it should be bled, but you shouldn't have enough air in the system that would allow a shutdown after hours of normal use...or a shutdown in a parking lot while idling.    Have you cracked the engine bleeder valve on the crossover between the thermostat housings?  You could rule out air in the engine right there.   As long as you get solid water?? 
Glad to hear you are back on the road!
Good Luck, JR

[Stan]

phil: I should have mentioned that you probably have two high water temperature senders, one on each side. On one side there are two that look the same. One is the sender for the temperature gauge and the other one is a high temperaure switch. The shut down sender should measure infinite resistance while the temperature gauge sender will show relatively low resistance.

[plyonsMC9]

Thanks for the additional assistance.  Also, thanks to Charlie who gave me a call yesterday.   

Yes, this is an ex-NJT.   Things ran fine with the defroster on the whole trip.  I turned off the coach heat, and left the defroster running - with that combination, no shutdowns.

I've still yet to use the "move wires around" technique - but I will give that a go this weekend.  Looking for shorts between my sending units.  Also, I will post a picture of the sending units, and any shutdowns I can find. 

Thanks again - you guys are the best!!!!!

Kind Regards to all - and a blessed new year!

Phil

[Hi yo silver]

MCI Types,
Correct me if I'm wrong, but isn't it possible to hold the start switch in if you have an undesired auto shutdown, in order to "get off the RR tracks"?  (I like that phrase, very appropriate)  When I was on a check ride for a local charter in an MC8, it happened to me, and if I remember correctly, (that's an iffy prospect), the instructor did that until we could go a little further to add water.  That was years ago, and I don't know if it's a common feature on these buses.  Anyone??     

[Stan]

On all the older MCIs the shutdown over ride was an option. At some point they may have made it standard. I believe up to the MC-7 it was a spring return switch, with  a red flip-up cover over it, that you had to hold down to restart the engine and to keep it running. On the MC- 8 they used the'hold the key on method' with a fuel pressure switch to keep the starter from staying engaged.

RJ or BusWarrior probably have all the details.

[buswarrior]

Hello

The MCI auto shut-down system on this vintage of coach may be by-passed by holding in the starter button. The engine will continue to run as long as the starter button is held in, (which will turn the end of whichever digit you are using purple and remove all feeling for the next while) and the pressure switch in the fuel system will take care of disengaging the starter.

I would be a strong supporter of removing the shut-down system, leaving all the instrument panel warning lights and sensors intact - alarmstats etc. Remove the system correctly, do not just cut wires to sensors!!!!

You own the bus, you will not keep driving it if the hot engine, or low oil pressure warning comes on, BUT... you want to choose the stopping place, not have the engine just turn off at that moment.

As the coach ages and develops ghosts and other electrical gremlins, having the auto shut down removed gets rid of one more variable to trouble shooting, and removes more failure points.

The shut down system was invented to protect the motor from stupid hired drivers who would keep driving the bus until the engine seized or blew up. No vested interest beyond their final pay cheque. That is definetiely NOT the mindset of any busnut I know!

Hmmm... has anyone else disconnected one of these systems and can provide the dirty details? Mine was not equipped, as the original purchasing fleet paid their drivers well, and trusted them to do the right thing when the warning lights came on.

happy coaching!
buswarrior

[NJT 5573]

phil, I fought a problem like yours with my 89 eagle, NJT. It is a ddec motor and I'm suprised yours is not. I was also on a steep uphill grade when I first had the shutdown. Fought it for a couple hundred miles. Everything looked good. oil, water,etc. Every time I got on a grade it shut down. I finally decided to put some extra oil in it since it was 2 quarts low maybe. That fixed it. I think the low oil shutdown must be at the drivers end of the engine. made me mad took it to DD and had them unprogram the shutdown feature. Now it goes like jack the bear!

[NJT5047]

my 89 eagle, NJT. It is a ddec motor and I'm suprised yours is not. I was also on a steep uphill grade when I first had the shutdown. !

DDEC was introduced on NJT MC9s in 1987.  DDEC 1 was used on 87 '9s.   Most '88s and all '89s had DDEC II .   NJT Eagles have wiring similar to NJT MC9s.   These are different Eagles.
Best, JR   
 

[Buffalo SpaceShip]

I bypassed my GMC's MUI over-ride for the very reasons Buswarrior suggests. Mine acted up once and now it's gone. It was a fairly simple affair of removing power to the shutdown relay and using that wire to power something else, IIRC. A few hours of probing and keeping my head in Da Book did it (and I'm fairly slow with these things). My tell-tales still work and shoud alert me to shut it down when and if it's needed... if I somehow forget to look at my gauges.

My reasoning was it could be more dangerous to have the engine cut out unexpectedly than to baby it someplace safe, even if "over-temped" and/or "under-oiled." And nuisance-tripping like mine (and Phil's) is just askin' for a roadside disaster.

Glad you got her home, Phil!

My $0.02,
Brian B.

[plyonsMC9]

No question - it was DANGEROUS when it cut unexpectedly on the uphill grade, curve.  From our post earlier in this thread - we were almost nailed by a semi driving at high speed half-way on the shoulder where we had just pulled into!  Missed our bus tail end by just a few inches.   

Brian, what are your tell-tales?  I'm assuming you mean  the mechanical temp guage & oil pressure guage?  Maybe the warning buzzers?  Or do you have something additional?

Best Regards,  Phil

[Buffalo SpaceShip]

Gads, Phil, I DID miss that part about your mishaps. Sooo glad it wasn't worse. Wow.

"Tell-tales" are the lights on top of my dash that warn about low oil pressure, high coolant temp, etc (pic below). These and the gauges are on totally separate senders, and neither were affected by removing the shutdown relay from the equation. IIRC, the relay senses grounds from the Alarmastats that run the tell-tales, and something in the old relay was sending the false positive to pull the shutoff solenoid. Probably just some bad contacts, but I don't really think I want that thing determining my engine condition.

It might not help you, since mine's GMC, but I'm also attaching a shot of my shutdown relay (now bypassed).

HTH,
Brian B.

[TomC]

We can thank the declining quality of commercial drivers for the advent of all the shut down devices.  Pretty much, companies want a vehicle that does all the thinking for the driver.  With practically all buses and a big chunk of big rigs with some sort of automated transmissions, basically they want the driver to push the go and stop pedal and steer-that's it!  So for the most of us that are VERY aware of our buses blood pressure and temperature, I think that auto shut down is for the birds.  Personally don't have them (except of course on the generator that basically runs without attention), but do have a good loud buzzer for low oil.  When the oil filter broke on my bus shortly after the get together in Rickreall, Or in '05 on California 299 (not a good road for a bus-very scenic-but a pain to drive-would be great in a sports car or motorcycle) I heard the buzzer, looked down and saw the oil light on and immediately shut down the engine-worried about where to stop after the shut down-and just happened to have a turn out on the left side of the road that I coasted to.

Personally speaking, I would defeat all shut downs if I had them, just like Brian did.  One other point, shut downs on trucks are good for those that idle their trucks all night-although that is going away also, because of smog emissions (personally never understood idling a 500hp engine to run a 10hp A/C compressor).  My old truck didn't have shut downs, neither did any truck before electronics-and mysteriously we got the job done anyway. Good Luck, TomC