bus will not shut down

[Jimmybefree]

hello,

I have a 88 crown with a 6/71 and she will not shut off when I turn the key to the off position, can someone explain to me how I can shut her down ? . thank you in advance

[turf]

i dont know the details of your motor but mine has a fuel shut off solenoid that goes bad. if you can find that solenoid, you should be able to pull it out and shutoff the fuel.

i've heard of throwing a towel into the air cleaner as well. never tried that one.


good luck

[Jimmybefree]

Originally Posted by turf

i dont know the details of your motor but mine has a fuel shut off solenoid that goes bad. if you can find that solenoid, you should be able to pull it out and shutoff the fuel.

i've heard of throwing a towel into the air cleaner as well. never tried that one.


good luck

thank you for your quick response. she shut off about 5 min ago ,but I do not know why, or where this fuel solenoid is .
Would they all be the same on this engine?

[Skoolydoo]

It was her way of saying I want to keep moving..good luck

[EastCoastCB]

Probably a mechanical lever or something. You gotta shut off the fuel on diesels to shut em off.

[Chevydude01]

Hi. I have a 1976 Crown with 671 5 speed. Mine did that one time. I understand there is some sore of magneto of some sort in the fuel pump that can get stuck and it will not shut off. I put it in third and dumped the clutch to stall it out. My 76 hasn't done it again. I don't know if this is much help but stalling it seems to work.....

[opus]

Whatever you do, dont ever try to dump the clutch to stall out a 2 stroke Detroit!

[Crown_Guy]

All 6-71 powered Crowns have an air powered piston actuator mounted on the top of the governor housing accessible from the left (driver) side engine door. The actuator pushes against the fuel shutoff lever in order to shut the engine down. That lever internally moves the fuel rack to zero fuel thereby shutting down the engine.

The governor is located just above the water manifold at the forward end of the engine. You'll see two levers mounted on shafts coming out toward you on the left side of the bus, when looking at the engine through the door. You'll notice the throttle linkage on one of the shafts, the other shaft has the fuel shutoff lever attached. A (usually red in the later builds) flexible colored plastic air line comes down to the air piston cylinder that pushes on the fuel shutoff lever mounted on the second shaft. The red plastic air line goes up to an electrically operated "Skinner" valve which is how the electric system controls the air shutoff piston.

The air logic requires that the bus air system be aired up in order to provide enough air pressure to operate and push the spring loaded piston against the shutoff lever. That means that you CANNOT shut the engine down until enough air pressure has built up(with the electrics). This may take as much as 5 minutes. That could be exactly what happened to you when you couldn't turn it off. If you tried to stop it right after starting it without any air in the system, nothing will happen until the air builds up. Just for fun, try doing that and see what happens. Start the bus with no air at all in it and turn the key off once it's running. It will run normally until enough air builds up to move the piston and then the shutoff lever. It may die slowly, or not, but it will shut off eventually. You should probably wait a week to make sure all the air is gone from all air tanks.

You can also reach in and manually move the shutoff lever by hand in order to shut it off. Clockwise as indicated by the direction that the air piston is pushing it. You can also move the throttle linkage to speed up the engine from here as well.

I'll mention a couple other bits of information regarding the Crowns and how to use the mechanics control panel located by the fan. The "safety" switch will disable the starter so that the bus won't start from the drivers seat. This of course to protect any mechanic working around rotating engine parts. This could sometimes cause you to think that the bus won't start, if the safety switch has been pulled down below. Another thing that will cause the bus not to start is if the neutral safety interlock switch on the transmission linkage is maladjusted, and thinks the bus is in gear. This will prevent a start as well, the way around this is to push and hold down the dashboard mounted "neutral safety overrule" button while cranking the engine.

The "ign" switch on the mechanics panel will turn on the ignition and allow for an engine start right from the mechanic panel. This way you don't need a key to start the engine, just do it from the mechanic panel. One caveat about running the bus using the under floor start panel, the Alternator will NOT be operating and no current will flow into the batteries. Take heed. Only use it for emergencies and don't run big electric loads. And the engine must be stopped from the mechanics panel, it overrides the key ignition switch.

One other thing that will definitely cause trouble starting normally is if the engine air damper is tripped, which causes a metal plate to drop down and seal off the engine air intake. This is tripped from the dash board by pushing the "emergency (stop)" button. All it takes is to do it once. It pulls a pawl out of a notch with an electric solenoid and allows the spring loaded damper shaft to slam shut. In order to reset the damper you need to open the left side engine door, and you'll see a button, little handle, or something like that, it depends on the build year, right through the left frame rail, and you give it a strong PULL, toward you, the left side of the bus. No need for rags in the air intake with this damper designed in. You can't really reach the air intake anyway, the blower is mounted on top of the engine, between the frame rails, just under the floor.

One other thing regarding stalling out the engine with the clutch while stopped. Besides being rather hard on your nice expensive 6-71 there is a more valid reason to not do that. Most people don't know it but a 2-stroke Detroit Diesel can actually run backwards. It's certainly not good for it and there isn't any oil pressure or fuel pressure for long either, but it can be done. It's usually initiated by a specific sequence of events whereby the drive-line components store up the stopping torque (much like a rubber band) and then release it back into the engine in the opposite direction which can start the engine off going backwards. The clutch will need to be depressed again of course for it to continue, but if the events are all done correctly it can be done. I know this from personal experience. I did it once many years ago with a GMC 4106 that was not very well maintained and all the drive-line and clutch assemblies were very loosey goosey. I was trying to pull away from the curb on a slight incline, and managed to stall the engine out, immediately the drive-line snapped it in the other direction and the engine took off backwards. It was very weird to look back and see engine smoke coming out of the air intakes and finally realize what was going on when the bus wouldn't pull forward. I stalled it with the clutch and left the clutch up to make sure it stopped for sure. It then re-started just fine, I took it to the shop and told them but it seemed to be OK. I've never seen or heard of any Crowns doing this, mostly because they have a very tight closely coupled drive-line configuration. But all Detroits can be made to run in reverse if things are done just exactly right. They were actually designed to run in either clockwise or counter-clockwise direction for Marine applications. They only need the appropriate camshaft, and one of the intermediate gears in the gear train are put into another position and they can be run in either direction. Maybe the oil pump too. Very nice design so you don't need a large inventory of spare parts on-board to work on both right and left hand running engines. Mostly all the exact same parts in each one.

[Jimmybefree]

Thanks Crown Guy for the detailed and thorough explanation. I had a feeling the first few times she wouldn't shut down immediately it was some sort of cycle that needed to be completed first. But this last time she ran for almost an hour and I was starting to get concerned.
So glad to hear that it's all ok and part of the system design.

[Crown_Guy]

An hour wait for it to shutdown isn't normal and indicates some kind of trouble. It could be any number of electrical issues where the circuit is not being made to the Skinner valve to activate and open the port to the shutdown air actuator. The air actuator itself may be gummed up and sticking and not moving freely when air is applied. This is definitely not normal behavior and should be investigated and the reason for it determined and resolved. Once air pressure is up there should not be any delay in shutdown. If there is, it is not normal, and means something is not working correctly. It may not be serious, and even easy to repair, but it needs to be looked into and resolved. One test is to give a listen when you turn the key to start the engine. You should hear a very definite air release "pop" from the Skinner valve as it opens the exhaust port and retracts the shutoff actuator piston. If you don't hear this (assuming air pressure is already up) that's a good place to start looking. The electrical connectors to the Skinner valve sometimes get dirty and causes poor connections. There's several places to start looking, but anyone with basic troubleshooting skills should be able to find the problem. At least you can be pretty sure the fix isn't going to be too hard or expensive. There just isn't that much that can be going wrong, a very simple and straightforward system with easily available replacement parts.

[Jimmybefree]

Ok thanks for all the info.

[sammy]

Do you happen to have rear controls for the engine? I have an 1988 Gillig Phantom (Detroit Diesel 6v92TA) with control in the engine bay to start/stop the engine. It wouldn't shut off the other day, and I just went to the back, flipped the controls to rear control and shut her down. The switched it back, and it's been fine ever since. Maybe something was wonky with one of those switches and it just needed flipped back and forth? That's what I'm hoping with mine, and maybe you have a similar setup.

[Crown_Guy]

It could easily be the safety switch on the mechanics panel. Or even the "ign" switch there as well. They need to make good connections internally in order for the driver ignition switch to energize the Skinner valve. If the bus has been sitting around for months and years before you got it, there's a very good possibility that many things are not going to be working very well until you can put lots of miles on it, and get things working again. It wouldn't hurt to move the switches on and off many times with the intention of cleaning up the contacts inside, this may clear it up just like the poster above experienced.

These types of vehicles thrive on being used and driven, lots. Sitting around causes more trouble than working them hard does. Every system on the bus suffers from sitting too long and not being exercised. The air system is one that really needs to be used or things will start getting strange and sticking and failing etc.. All kind of things act funny with the air system until you put some miles on it and get them all loosened up and lubricated and operating properly again. Some electrical systems could give the same symptoms, where plain 'ol daily use solves many problems. I know you probably don't intend to use it every day, but anything you can do to drive it as much as you can will show you clear improvements in how it all operates.

Crowns were built for daily service and a service life of over 30 years. Most private charter operators ran them over 100k miles a year for 20+ years. they are built to be driven, and when they are the systems run smoothly and give very little trouble. I'm currently driving commercially a Crown like yours with a 6-71 in it that was in storage for 5 years or more. We cleaned it up and got it back in shape for commercial service, and I've been noticing that as I drive it things keep getting smoother and seem to be operating better. The constant use makes things better and causes far fewer problems than if it's only driven a little bit every once in a while.

[Jimmybefree]

I was fortunate enough to pick this up last September from the bus barn where it had sat for 9 months or so after being decommissioned due to noncompliance with recently changed environmental standards. I've been turning it into my home and have let it sit since getting it but plan on driving it to my home a thousand miles away in mid-April.
I found a company who may insure it but they say it must be "finished." What's finished? A kitchen sink, a bathroom and a bed. So that's where all my energy is going right now. Then once it's insured I can take it to the scale as my state requires a weight before they will issue a title.

[Jimmybefree]

I love hearing the way you describe these buses. I found mine on E-bay a week before I bought it. I fell in love with the body style and after researching all about Crowns, I decided to bid hard. I saw that some had gone for up to $10k so put my high limit a little over double what I could comfortably afford at $5050. Bidding stopped at $4550.
After hearing the things you say about it, it makes me feel like I got the right one.

[opus]

You may not have got the most powerful engine, but out of all the Detroits, you got the most durable!

[sammy]

Try just getting commercial insurance on it through progressive. Not as cheap as RV insurance, but it'll work until you have it completely converted. Should be able to get it for $500-$1,000/yr

[Jimmybefree]

Progressive says they don't cover bus conversions. Any other ideas where to look?

I have a new question. On the way home the speed-o-meter was working just fine and then all of a sudden was reporting speed and distance readings about ten times too fast. I assume it's a bad cable.
Does anyone know where I can get a new speed-o-meter cable?

[Chevydude01]

Oops. I knew not what I did! Forgive me! Believe me it was a move done out of sheer panic. I had only had my bus for a day or two and I was showing it to my friends, I took them for a quick spin around the block, about half a mile or so, then parked it and tried to shut it down. Nothing happened. I tried to use the Safety switch underneath on the engine bay control panel with no luck. I panicked and stalled it. Live and learn I guess. BUT, before I started driving I let it get up to 100psi. Does it need to be the full 120 psi to shut off at the key? Also, my engine control panel has a Safety button, Ignition button and a Start Button. No shut off switch on this panel? I have never tried to start it from here.

[Crown_Guy]

A couple of thoughts Chevydude01. First is that you don't need full air pressure for it to shutdown, but as you indicated, you started driving with 100 psi on the gauge(s?). As a normal part of the pre-trip safety check for all buses with air systems, its a very good idea to watch the gauges and make sure that the two air gauges are coming up as they should. The first gauge is on the Primary air system and the second is on the Secondary system. With no air at all in either system, normal is for the Primary air system to build up first to about 60psi and then the Secondary starts to come up. When they are the same pressure they then will build up together until they reach the 120psi cutoff pressure. You should then pump the service brake repeatedly until you lower the air pressure enough to hear the low air warning buzzer/light come on and take note of when that happens. that will verify the warning system is working, and watch the air pressure gauge to make sure it comes back up. After full pressure is back, pump the brakes pedal again down to about 90 psi and watch for when it starts to build back up again. that will show you where the air compressor governor is set. It should be about 85psi. Everyone who owns and drives any bus, especially one with air brakes should make the effort to acquire for themselves the written instructions for how to make and perform all the pre-trip checkouts that all commercial drivers do on their vehicles. You will be safer and possibly catch incipient problems before they cause you trouble or even risk your life. This information is easy to find and I can't stress enough how important it is to know how to do these checks. One thing for instance, how long has it been since anyone has actually checked and drained the "wet" tank on their bus?. That's a big one for folks in cold country. All air tanks have drains, and the first one (wet tank) is the one that gets the most condensation, and should be drained daily before driving. Sorry if I seem to preach but I've seen enough new owners driving their newly acquired buses without the very first clue on how things work, or how to properly check them out before driving. They should be operated with the same serious attention that the commercial operators, and drivers, did when they were in service. There are good reasons for that.

Back to the shutoff issue. First: no it shouldn't need full pressure to shut off. I think the air for that comes from the Primary system so it should be at least 60psi before the Secondary gauge even reads. Second: I suspect that you may have a sticky air actuator piston (the thing on the governor housing) that pushes the cutoff lever. Or, as I said before there could be a number of electrical gremlins that aren't completing the circuit to the Skinner valve. As to the mechanics panel, there are usually three controls. The "safety" is a PUSH-PULL switch, and cuts out the starter. The "ign" is also a PUSH-PULL switch like the safety and allows for a start by hitting the "start" BUTTON which is a momentary push button. The "ign" IS the shutoff when you are done running the engine. Push it back in and the engine will stop running. PULL to run/start the engine, PUSH it back in to STOP the engine. And it overrides the drivers ignition key/switch. So be sure it's all way back in before trying to run normally from the drivers seat. This may be a clue to why it won't shut down sometimes, if the mechanics "ign" switch is being activated through an internal faulty contact or something like that, it will override the ignition key trying to shut down the engine. This is what I mean by checking for the various ways the electrical system may be causing intermittent failures. Simply exercising it a few times may fix it up...or not. Welcome to the club.

With the bus safely in neutral (be sure to check first) go down below and try starting the engine using the panel. Assuming you already have air pressure, make sure the "safety" is PUSHED in, then PULL out the "ign", you should and must hear the release of air "pop" from the Skinner valve right there close to you, you should also see the shutoff air cylinder piston retract allowing the shutoff lever to move counter-clockwise about 1 inch. If all that is working, then PUSH the "start" button and it should fire right up. To stop the engine just PUSH the "ign" switch back in. You should see the air piston come out and push the shutoff lever clockwise to zero fuel on the fuel rack in the engine. Just so you don't have to feel panicky about how to stop the engine if your system ever fails to work correctly, you should note by now that the engine is being shut down by having the fuel shutoff lever being moved clockwise and held there until it stops running. There isn't any reason you can't use your hand to rotate the shutoff lever and stop the engine any time you want to. This is how you can overcome system failures and take control of the engine as any mechanic would when working on the engine and systems. I've even had to remove the air actuator assembly from the governor completely when an electrical fault prevented the Skinner valve from releasing the air from the line so the engine could start. I drove normally and when ready to shut it down I just used my hand and moved the shut-off lever until the engine was stopped. This was on an MCI coach which has a much more complicated electrical system, but the basics of how the electrics control the engines are all the same.

Knowing how the systems work and operate the throttle and engine control levers on the engine governor you can increase your confidence level and be secure in your ability to manage problems when on the road, and get the bus home, without having to make expensive road service calls.

Crowns are very reliable and are not too complicated in their systems, which is one of the reasons why they are so beloved by the operators who have been using them for the past 60, almost 70 years, and are still in service today by anyone who can manage to hang on to them and beat back the Government Cartel out to destroy and take them away from the operators. They still work better and cause far fewer problems for their operators today than any of the new whiz bang things being pushed on us today by the corrupt Government-Manufacturer complex.

Learn about your Crown, and gain that internal understanding of how things are working, and how to keep them working, and even work around problems, and I can promise you a long and happy association with it. If you take the time and keep it properly maintained while at your home, I think you will find that it won't ever leave you along the side of the road with an expensive tow or repair to get it home. I'm not saying things can't go wrong, but I have been able to, over the years, get the Crown home by applying what I know about how they work, and overcoming the minor faults in order to limp it back home. That's both in commercial service as well as with my own private Crowns. A little knowledge is a lot of power.