emergency engine shutdown Detroit diesel

[tombuchanan]

I just bought a 83 MCI Crusader II and was driving it home when the engine shutdown with no warning.  I checked the engine and didn't see anything screaming a problem so I tried starting and it started right back up.  I drove the last 15 miles home with no issue.  I've read in the manual since then about emergency engine shutdowns but a label on the driver's console says this bus isn't equipped with one.  So 2 questions, anyone know what else this might have been or if that's the only possibility, where should I start as to figuring out why it tripped.  The water temp was around 200 when it happened, the oil pressure gauge wasn't working but the oil level was fine. 

[luvrbus]

The Skinner valve on the rear bulk head will loose ground and shut it off check the grounds

[Lin]

If the emergency shutdown was tripped you would have to reset it manually to start up again. 

[richard5933]

I assume that you're talking about some type of engine protection system, not the emergency flapper, correct?

If the label states that the bus isn't equipped with on, then I agree on a loose connection going to the Skinner valve as a good first approach here. If yours works like mine, the default (non-powered) setting is to have the valve send air to the shut-down cylinder, so if you have a momentary loss of power to the Skinner valve it will shut things down.

[chessie4905]

200? Were you climbing a grade at the time? Coolant level ok? Make sure to get a working oil pressure gage. If coach had been sitting a while, intermitant or sudden
electrical connection issues are common.

[luvrbus]

Why would you want the emergency shut down ? DD did away with those in 1980 and went to the spring loaded fuel tubes 

[TomC]

My 1980 Kenworth with 8V-92TA did not have the emergency shut off flapper valve. AND when my 8V-71 was turbocharged, the emergency flapper valve was removed. I used the now empty wire and switch on the dash to power my radiator misters. Good Luck, TomC

[richard5933]

Getting confused here...

At the beginning it sounded like we were talking about something which shut down the engine, and then the engine being able to be restarted with nothing being done other than taking a look and seeing nothing amiss.

The question asked by the OP was how could this happen if his bus doesn't have an emergency shutdown, which I took to mean a system designed to shut down the engine in the event of a low oil pressure or high temp situation.

The engine shutdown air cylinder would act in the same way if power got cut to it, since it's often what's used to activate an engine protection shutdown.

The engine flapper is a whole other subject, and usually the question there is something about how to reset the thing. Since there was no mention of resetting the flapper, it sure didn't sound like there was one involved in this discussion.

[luvrbus]

All shut down systems were added by the OEM on a Detroit some tripped the flapper, as you guys call it other worked off the skinner valves or used the all in one shut down cylinder as he said his engine does not have a shutdown system, you see different system on those engines like Murphy,Kasier and others   

[tombuchanan]

i wasn't on an uphill grade but might have been on a downhill when it happened.  the oil light came on at about the same instant as it shut down, I couldn't swear slightly before or after.  I just assumed that the light came on because the engine shut down because it went off as soon as i restarted it.  When i checked coolant the next day, it was low by about a gallon but i'm not sure if it was full before i brought it home.  i found 2 valves on the bulkhead which I assume to be the skinner valves.  they have a wire harness coming out of them that is sealed off.  Do they get ground from where they are mounted or would it be in the harness?  the harness goes to the breaker box which I haven't gotten into yet.

[tombuchanan]

i replaced the oil gauge in the back with one from an old air compressor and oil pressure seemed ok but then it stopped working so I ordered a real oil gauge but haven't been able to start the engine since I'm currently fixing an air ram leak.  the needle on the gauge up front moves backwards past 0 when i rev the engine.  Any idea as to whether that means the gauge is bad or the sender?

[richard5933]

The two Skinner valves are likely fast idle and engine shut down.

The low coolant could be coincidental, or you could have a low-coolant sensor built into the system in spite of the label indicating otherwise. But, if a low-coolant situation caused the shut down, you'd think that you would have seen a dash light turn on just before shut down.

The low oil pressure should have happened prior to the shut down if it was the cause of it. I agree though that if the engine suddenly shut down it would almost immediately trigger the oil dash light, so without knowing which came first it's hard to say definitively it was the cause.

I'm still thinking that this sounds like a loose connection somewhere which caused the Skinner valve to momentarily lose power, resulting in it failing to keep the shut-down air cylinder from shutting down the engine. If the Skinner valve lost power for a moment, the shut down could happen before the air could be restored to the cylinder.

If you have Amphenol connectors on the Skinner valves, it might be a good first step to unscrew them and check for corroded terminals. Wouldn't be surprising if there were.

[hogi6123]

the needle on the gauge up front moves backwards past 0 when i rev the engine.  Any idea as to whether that means the gauge is bad or the sender?

They're both working.  They're just not matched correctly.

Gauges and senders can be built in two ways.  When the oil pressure increases, either the voltage increases or the voltage decreases.  The gauge and sender need to match.

I had a similar problem, and replaced my sender.  Details are in this thread:
https://www.busconversionmagazine.com/forum/index.php?topic=34843

[neoneddy]

Had similar happen to me on my first day of ownership. Scary for sure. Turned out to be a loose wire on the shutdown thermostat.  If it touched ground the engine shut down.

When that happens the low oil light will flash too. There is low oil pressure when the engine isn’t running oddly enough.

You mentioned downhill, that makes some sense of your oil is a tick low. The pickup was middle / rear, so if you’re downhill you could suck air and trip the low oil pressure light.  I run my oil 1/4 past low, I had this happen to me when the engine goes idle a few times over the years after a long run.

Add some oil, see if shows up again, look for lose wires. Take a deep breath and work the problem no matter who is honking.

[tombuchanan]

so the skinner valve supplies air to keep an air solenoid from shutting down the engine?  If so, could low enough air pressure trigger a shutdown.  This thing had air leaks all over and the lady who sold it to me had to gun the engine for 15 minutes to get air pressure to build up enough to release the parking brakes.  So is it possible that letting up on the throttle while going down a hill could lead to the air pressure to drop enough to stop the engine?