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Bus Discussion => Bus Topics ( click here for quick start! ) => Topic started by: tombuchanan on December 21, 2020, 03:31:50 PM
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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.
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The Skinner valve on the rear bulk head will loose ground and shut it off check the grounds
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If the emergency shutdown was tripped you would have to reset it manually to start up again.
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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.
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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.
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Why would you want the emergency shut down ? DD did away with those in 1980 and went to the spring loaded fuel tubes
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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
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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.
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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
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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.
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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?
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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.
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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
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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.
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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?
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No, air pressure is used to shut it down, not keep it running.
Low or no air, the engine can't be turned off.
Happy coaching!
Buswarrior
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Usually they need air to shutdown, without air they will run even with power off.
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I hate to think operating coach with air pressure so low it could trigger engine shutdown. What about brakes?
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I hate to think operating coach with air pressure so low it could trigger engine shutdown. What about brakes?
Ha! Chessie, we are so behind the times... nobody worries about compliance or its connection to practical matters as mundane as brakes. I learned all this on the internet, cuz i am failing at being hip...
Happy new year and
Happy coaching!
Buswarrior
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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?
No. You could have a catastrophic loss of air in the system and the engine will not automatically shut down. The brakes should automatically apply though, so be prepared for the bus to come to a pretty quick stop if they are working.
Before you go down a wild goose chase looking for a system fault which might have caused the engine to shut down, have you confirmed that everything with the Skinner valve controlling the shut-down cylinder is functioning properly?
The Skinner valve is an on/off switch for the air going to the shut-down cylinder. As long as it has power, there is no air flowing to the shut-down. If the Skinner loses power for a moment, air will flow to the shut-down cylinder and the engine will stop. Even if power is restored to the Skinner right away, the engine may still shut down due to the time lag of the air cylinder releasing.
So, please let us know if you've confirmed the Skinner valve is in good condition and that the wiring is solid. It's possible to test the Skinner valve with the engine not running as long as there is air in the system.
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that's been my plan to test it but I'm in wisconsin and I don't see that engine starting until temps rise a bit. I'll post again when i'm able to test it.
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any advice on best way to test? start the engine and jiggle the wiring on the valve to see if it triggers the shutdown?
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Where in Wisconsin are you? I'm in Waukesha County, and if you're near to that maybe I can lend a hand when you get to the point of trying to start it and do some testing.
The Skinner valve that controls the shut down air cylinder won't really do anything until you have air in the system. That's actually a problem with the air-powered engine stop - if you need to shut off the engine before enough air has built you'll have to do it manually as the shut-down cylinder won't do anything.
Once the bus has air built up, if you flip the switch (or turn the key, or do what ever you do to shut off the engine) the Skinner valve will send air to the shut down cylinder to move the governor to the 'no-fuel' position. Once the engine is off, if you turn it back on but don't start it, you should hear the air cylinder venting and the governor snapping back to the 'fuel' position.
You don't even need to run the engine at this point once things are aired up. If you have a way to air up the bus without running it, you might be able to test it without even running the engine. Turn on the switch and watch to see that the shut-down cylinder vents and backs off. Then with the switch still on, start jiggling wires to see if you can make it extend the shut-down cylinder again. There might be a time-out on this system. Mine will keep the governor in the 'fuel' position for about a minute before it times out and I have to power off briefly and start again.
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I'm in the Twin Cities area, if you're close to the western side I might be able to come by. I'm not too much of an expert, but I've dealt with a few issues like this.
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If I may ask, how long of a time between the shutdown and restart?
Not sure if the mc9 has the same feature as my mc8 but at about 200 degrees the engine shuts down to protect itself. I've hit this a few times when I first started out before I learned to drive by the thermostat not the speedo....
I saw also that you mentioned that your manual said it doesn't have it, possibly aftermarket?... people do weird things to these buses during their life....
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If it’s real close to 200 , I’d restart as soon as possible to get it to cool down.
I had mine do it once in a construction zone up a hill in SD. I had no where to pull over, so I shifted down and held the master switch in. It kept running then the alarm stopped and it cooled down on its own with the higher RPM.
In my opinion, letting an engine sit and cool is worse than running it to cool. The pistons and liners all have heat that is now not being carried away by water, so they will actually increase in temp before coming down. You’re better off getting it to high rpm and low load to get it cool, keeps everything moving.
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If it’s real close to 200 , I’d restart as soon as possible to get it to cool down.
I had mine do it once in a construction zone up a hill in SD. I had no where to pull over, so I shifted down and held the master switch in. It kept running then the alarm stopped and it cooled down on its own with the higher RPM.
In my opinion, letting an engine sit and cool is worse than running it to cool. The pistons and liners all have heat that is now not being carried away by water, so they will actually increase in temp before coming down. You’re better off getting it to high rpm and low load to get it cool, keeps everything moving.
Good advice they are supposed to shut down at 210* when that happens most of the time the temperature keeps rising till they are cooked well done ,The 1st warning buzzer (205*} or lite should be kept in good working order it will save you big $$$$
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thanks for the offers of help, but i'm in central wisconsin. it finally warmed enough to start it so i tried wiggling the wires on the valve while it was running and nothing happened. but, it hadn't run long enough to reach operating pressure so I'll have to try that again. As for temp, I believe it was around 200 when it happened. is that really hot enough to trigger a shutdown? it restarted after about 4 minutes
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The first issue, the dashboard gauges on these old buses are notoriously inaccurate.
Using the infra red heat gun on the pipes, down thru the floor into the engine room at the back, while actually making driviing heat, let's you "re-calibrate" what the gauge really means.
For instance, mine was good at 180, and rose quicker than the real temp beyond that, so 195 or so, was really 190, but they are all different.
An old detroit 2 stroke that is really showing 200 degrees has approached the precipice... you really don't want one that warm...
Happy coaching!
Buswarrior
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2 strokes do fine at 200 degrees that is normal temp 195* to 200* on generators with 2 stroke but in a bus that doesn't give you much room for temperature rise ,Sean Welch ran his 8v92 in his Neoplan for years at 200*but he watched it close
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Thanks for info, but will a temperature around there trip the engine shut down procedure? That was my main inquiry as I'm reluctant to take it out again without knowing why it shut down the first time.
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Good evening Tom,
I've had my MC9 engine shut down due to "temps" many times and reasons. You mentioned you just purchased the bus and then it shut down on the way home. Once right after I had my first coolant change after purchasing the bus. It turns out my MC9 was finicky and took some effort to burp after refilling w/ coolant. So driving back from the shop the engine circulated some kind of air bubble, and * alarm * shut down in normal driving conditions. First time was hair raising - especially trying to get out of traffic. 2 or 3 other times the bus was serviced and same scenario. I learned to watch coolant level like a hawk. And have lots of talks about burping the engine w/ whoever worked on it, which didn't seem to help. And doing lots of coolant top-offs and watching of the radiator site glass. Later I had a great mechanic, Joe M., who put in a kind of air bleeder and haven't had that issue since.
Also had the situation where temp sensor wires crossed the engine or shorted out against metal - If I remember correctly, the sensor wire wasn't properly insulated at the time. Put it in a wiring loom until I could get the wire insulated as it should be. That 'short' also shut it down 2 or 3 times.
Before I replaced the radiators the engine ran hotter, which of course shut it down especially in long slowmountain grades. For that I worked at downshifting, and driving by the temperature gauge vs the speedometer. Not going all that fast anyway. That was a huge help. And I do the downshifting to this day just to keep temps where I like them.
If you knew the differential between the true temp and the dash gauge that would help also, so you would know what temp you're actually running. Others have noted the inaccuracy of the dash temp gauge. Testify!! Run the engine to temp, grab the heat gun and have someone read the dash gauge to you while you read the heat gun. Keep the differential in mind if it's off.
Eventually you will nail it, and know your engine and the temp shutdown will likely be a thing of the past - but you will always keep it in mind as a savvy driver who knows his rig!
Hope this helps, Phil
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Keep in mind those sensors come in different degrees for shut down,a friend of mind replaced his sensor and paid no attention to the little detail and install a 180 degree sensor and his MCI would not go around the block before shutting down
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thanks for the info phil, I'm guessing this was my case. I know the coolant was low and temps were somewhere around 200 when it happened. where are the temp sensor wires on the mc9? i can see the sensor wire for the gauge back by the engine (which doesn't work) but i don't see where the one from the front is.
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I have a 1980 Prevost, so it may not apply, but my 6V92 shut down 2 times on the interstate on the same day. (that was fun)
All fluids fine, all gauges in the "green"at shut down both times. It would start again after 5 minutes, but then guages would go dead and jake would not work. But the bus still ran, so went to a repair place 2 hours away with fingers crossed. It was the engine run relay. Don't know if you have one of those. Hope you get it worked out.