MCI 9 Shutting Down

[Doug1968]

Fellows,

I purchased an MCI 9 (1981) that was converted when new by Pawnee Coach. This coach was located in Post Falls, Idaho and while bringing the bus home it died, shut off, just as though someone had shut the switch off. This first happened at the owners house while we had it idling and then again when I was coming to a stop in a parking lot a few miles away.

We put a call into a fellow bus nut who told us to look at the possibility that it was being shut down by a false signal to the auto gard system. I isolated the two sensors, one oil pressure and one temperature, that when disconnected left the gauges operable in the dash and disconnected them.

Both times the engine died it started right back up and ran as though nothing has happened?

We had about a 450 mile drive back to Portland so we left Idaho and the bus ran flawlessly for four hours until we stopped for dinner. After dinner we jumped into the coach and took off to complete the last 100 mile leg home. Cruising down the Columbia Gorge at 60 miles an hour after dark everything seemed to be great. I had got past the jitters of having never driven this bus and after the four hours of a very smooth ride visiting with my wife I was feeling pretty good. Then, without any warning, the engine died, the lights went out, and I found myself trying to bring the bus to a stop without hitting the guard rail. No lights at all and white knuckles like you wouldn't believe. Turned the switch and she started right up and we came the rest of the way home. Scary to say the least!

I am open for ideas as to what to look for to solve this problem? When it dies I lose all power, lights and everything.

Maybe someone has had a similar situation and can steer me to the problem.

Thanks, Doug

[grantgoold]

Perhaps you have a faulty rear engine start switch? I would also replace both temp and oil sensors as perhaps they are faulty as well.  Sure would fix the problem before I took the bus back out for a long ride.  How was the temp at the time of shut off?  Can you confirm actual engine temp as compared to the dash gauge using an IR gun?

Just throwing out some ideas.

You may also want to check with tech support at MCI.

Grant

[B_K]

"When it dies I lose all power, lights and everything."

But sounds to me like loose wiring or ground at or to the main switch.
If it were just the engine dying without losing lights I would be suspect of oil pressure, fuel pressure or temp shut downs.

But somewhere either in the main switch wiring or in the panel outside under the drivers window it has a short or loose connection.
  BK 

[bevans6]

I'm with BK on it being an electrical issue.  That vintage of MCI doesn't actually need electricity to run after it's started, with one exception - the master switch sends power to the engine run switch, which in turn powers up the Skinner valve that opens the engine stop lever on the governor.  So with no power to the Skinner valve, the engine stops.  The master switch also sends power to the headlight circuit.  It doesn't send power to the turn signals or clearance lights, so you could experiment there some.  Schematics are available here:  http://busconversion101.com/PDF_Files/MCI%209%20Maint%20Manual%20in%20PDF%20format/MC-9%20-%20Maint%20Manual%20Section%208.pdf

Brian

[luvrbus]

Doug,on the fire wall check the skinner valve that controls the engine shut down it could be a ground or the skinner valve it's self , I would bet it is the skinner valve are you and Lori coming this way soon ?  

If so just plug the air line to the shut down and we can fix it here our 8 would do the same thing when the engine shut down I lost all power

Under the drivers window there is a 30 amp breaker #4 the only 30 amp breaker there the master switch feed they go bad also

Now with 2 buses and a motor home you are serious about retirement  

good luck

[bevans6]

I had a quick look at the schematic for the MC-9.  Clifford is correct, the 30 amp breaker feeds the master switch which feeds both the skinner valve and the headlights.  The turn signals and the clearance lights are each fed with separate breakers from the master 24V bus bar.  If they stay on and working when the bus shuts off, then suspect that 30A breaker and things associated with it.  If they go off and don't work, suspect the master battery disconnect switch in the front luggage bay - it's the only thing in common with all three and feeds the master 24V bus bar with cable that runs across to the AC electrical panel and then forward to the main electrical panel.  If the engine stops but the headlights stay on, then I would suspect the skinner valve and things associated that control it.

Brian

[robertglines1]

If all else fails the ford like solenoid if front elect box went out on my old MCI 8 once it is the feed controlled by switch that tells everything else to power up.  Could be intermittent there.  Mine was.  Hate elect ghost.  cheap  fix..

[Chuck Hancock]

I had a Country Coach that would shut down when it took a notion.  Turned out to be a faulty shut down switch, but that can't be the problem here if you loose all elec.  almost has to be at the master switch.