Bus shutting down

[platinum mci]

Bus is a 1983 MCI 9  6v92ta.  Changed the oil in the bus yesterday everything worked great, started ran fine checked the oil good to go.    Today checked the oil its at the full mark started up ran for 20 seconds shut down,  bus does not have emergency shut down.  So i checked oil level everything good started back up and watched as it is building air pressure the shut down piston that is air operated is slowly extending and moving the shut down lever. Traced the air line to the fire wall were it connects to a valve. Is this valve the problem or something else?

[junkman42]

Assuming that the valve on the firewall is a electric solenoid, disconnect it and see if the piston still extends.  If it does the valve needs attention.  You can also check and see if it is getting voltage to the solenoid when it should not.  Try rapping on it while the engine is running and see if the piston stops extending.  Good luck,John

[Tenor]

To keep the engine running while you check the shutdown system, take one bolt out of the piston housing and swing it away from the rack lever. 

Glenn

[platinum mci]

I have found that there is no power going to the solenoid valve  tracing the wires out I have also found out that the valve should have power when the master switch is on.

[Tenor]

Yep, that's the culprit.  Now, look for the number stamp on the hot wire, and find it's match in the engine compartment electrical panel and see if you have power there.  If you or anyone else has the schematic, it or they can tell you which stud that wire attaches to and see if you have power there.  Repeat the procedure to the driver's electrical panel etc.  Good luck!

Glenn

[Tony LEE]

Just a thought - make sure it is not the low coolant level switch that is causing the auto shutdown

[platinum mci]

no power going to stud 53 and 54 on the rear panel as per the schematic, if any one else has the schematic any  advice would be great   was able to get the bus going by applying power to 53 so I could move it.

[gus]

Do you have a mechanic's engine shut off switch in the engine compartments like on some GMCs?

[platinum mci]

no has a remote start for front and rear start. but no shut down switch

[gumpy]

Put your remote start switch back in the run position. Sounds like you left it in the stop position.

This could also be a fuel pressure switch, high temp, low coolant, or low oil pressure. I've had problems with the fuel pressure switch on mine. My friend had problems with high temp switches.  They all activate the safety shutdown.

Incidentally, if you hold the start button in, it should override the shutdown system and allow you to move. Of course that assumes your shutdown system is fully in tact.

craig

[gus]

These are two separate switches;

Start is a spring loaded switch which returns to No Start when released.

Run -- Stop is a two position switch which will stay in either position.

At least that is the system for a GMC.

[NewbeeMC9]

I second gumpy,

Check the rear run switch first,   I found that one out the hard way    But I knew right where to look because I had seen it here.

I had bumped mine, but it is freaky when the bus shuts off all of a sudden and sets off that panic mode



Let us know

[platinum mci]

I will recheck the remote switch's and try to  restart this morning.   There is a name plate on the dash that says this vehicle is not equipped with emergency shut down. I'm assuming that this means it does not have a shut down for low oil and high coolant temp, I'm I wrong?

[Old4103]

It means that there is no emergency shutdown flap in the air intake above the blower.

The emergency shut down is for runaway engine or other uncontrollable conditions ONLY.

The auto shut downs (low oil pressure, High Temp, Low Coolant) are a different system.

I will recheck the remote switch's and try to  restart this morning.   There is a name plate on the dash that says this vehicle is not equipped with emergency shut down. I'm assuming that this means it does not have a shut down for low oil and high coolant temp, I'm I wrong?

[platinum mci]

Wow thanks for the advice I feel stupid,  well In that case let the fun begin on finding this problem.  I will first go out there and check to make sure I didnt bump the remote switches.