| Author | Message | ||
| Steve Zona (Highwayrunner)
Rating: N/A |
Hi All. need info. I broke down on the highway the other day. engine shutdown, couldn't figure out what was wrong. dash lights showed "hot engine" and "low oil" I checked the oil and it was full, and the engine was not overheated, manual temp gauge in the rear reading 185. took one bolt out of the telltale and moved it aside. started the engine just fine. still had hot engine and low oil lights on but not correct. drove to campground... about thirty miles with no problem and showing 185 temp and 60 psi oil. tied starting next morning and with telltale connected it shut the engine down as soon as it had air pressure. about three minutes. where do i start with this, bad sensor ? or relays? or am I even on the right track. any advice will be appreciated Steve and Cindi 82 mc9 | ||
| H3-40 Rating: N/A |
Steve is this a DDEC? If so it's probably a sensor which is usually the first to go and give false signals. Mine was the low coolant sensor. It shut mine down when cold! Changed the sensor and it's never shut down since! Ace | ||
| Steve Zona (Highwayrunner)
Rating: N/A |
sorry i did not give enough info. it is an 82 mc9 with 740 auto not ddec 6v92ta | ||
| John MC9 Rating: N/A |
Re: "dash lights showed "hot engine" and "low oil" I checked the oil and it was full, and the engine was not overheated" Through the years of troubleshooting any/all things other than buses.... I've found that with electronics, when there are two or more problems at the same time, you'll usually find the problem with the item common to both/all... Check the grounds (at the engine, relays, etc). Loose connections and poor grounding at the rear or front electrical cabinet, can raise all hell. If you don't have Dah Book, the pinouts for those boxes are here: http://www.dialup4less.com/~aabn/MC9_docs/ | ||
| Bill 340 Rating: N/A |
Steve Dont get too frustrated with some of the guys on this OR other boards, as a lot of them will do more driveing on the boards than they ever will in their coach, Also some of them will spend a LIFE TIME CONVERTING THEIR COACHES SO THEY NEVER HAVE TO TAKE THEM ON THE ROAD, Now i know I will get flamed for this statement, but its ok.The amount of true knowledge on this and other boards is UNMEASUREABLE, and we all hope it continues forever, Some comments are purely in fun and some just vicious,dont let the the wrong ones get to you, you probably will never meet them on the road anyhow.Ian does a great job putting us all together, Now its up to us to make it go, My hats off to all the great EXPERIENCED comments. and my best wishes to those that think they know everything.NOW as for your problem I do not know the answer, just keep asking, as replys tend to wander away from the original question, P.S I have been on this board since the begining and have a physical problem which makes typing hard for me, But today I had had it, your broke down and asking your board friends for help and jim has tried to help and pete added his oil pres to help. AND then the real intelligent spoke!!!!!!It took a long time to type this so I hope they will take a long time Blasting me for it. Good luck Steve Bill 340 | ||
| H3-40 Rating: N/A |
Bill, I tried to help in thinking he may have had the same problem mine had but he stated afterwards it wasn't a DDEC so it must be a bad ground of some sort! Hope your doing ok!  Ace | ||
| Ian Giffin (Admin)
Rating: N/A |
Steve, I apologize that someone wasted your time with his inappropriate comment. I have deleted the offending messages. Thank you for your continued support of this web site and our bulletin board. Best regards, Ian www.busnut.com | ||
| Bill340 Rating: N/A |
I must apologize if I was misunderstood by a few as I never meant that the post by Pete RTS, which I thought was meant as amusing and positive not a negative, or the post by AceH340. I also thought his was helpful. There was only one post that was thought to be negative and I noticed that Pete RTS posts was also removed. As I am not the moderator, I don't have a decision in what stays and what doesn't as I know Pete and Ace both personally and would call them and tell them if I thought it was inappropriate. I was just, after years of sitting here and people ask a serious question as I did one day, typed in a question which I really wanted to know the answer to. I got 16 responses, one of them tried to help, one of them made a smart comment about government conspiracy and it went from there with 14 more replies to do with the government and conspiracy and I never did get an answer. And, I've seen that done so many times over the years. As I think the humorous comments are really quite funny but we also have to remember that when someone types in stranded on the road that should have first priority. Sooo, let's make them laugh and see if we can help them. And, Ian I commend you for removing the smart comment that was posted and just in case some of you think that I'm not having any trouble typing all of this, I'm really not as my wife is typing this segment for me as I speak. Overall, I think it is a wonderful board. Sorry if I created any confusion for any other member. Bill 340 | ||
| H3-40 Rating: N/A |
Whew, I'm sure glad we got that cleared up! For a moment there I thought... well just you never mind what I thought! Give us a call sometime if were still on your good list! LOL Ace | ||
| John MC9 Rating: N/A |
Holy Carp.... Waddimiss? Jeez, I have just got to hang around a thread longer... Steve - How'd you make out? | ||
| DMDave Rating: N/A |
I hate when i miss the good stuff. Hi Bill and Bren, we will make Arcadia this year if we have to walk! | ||
| Bryce Gaston (Busted_knuckle)
Rating: N/A |
Wow what I'd miss? Steve I tried to respond earlier but my computer crashed, any way let me start by tell'n ya don't let the bashers get ya down I don't post as much as I lurk thesedays for the same reasons, but when someone's got real troubles I try to help! I run a shop and kep my dads charter buses on the road, so with that said I hve to agree with JohnMC9 on checking for bad grounds, but first lets try something else! On each thermostat housing there is a shutdown sending unit(on the right side there are 2 sending units 1 is for the temp gauge) ok to start with leave the shut down cylinder (i think you are calling this the "telltale") to the side while you build up air. Once it has built up air pressure try removing the wire frome the sending units one at a time if the cylinder shaft retracts that sending unit is bad! Just replace it and happy motoring! Now if removing these wires does nothing for the cylinder, you still have a problem, I'd remove the top inside access planel if possible to gain access to the top of the engine, from there follow the air hose from yer "telltale" or shutdown cylinder to the skinner valve that controls it mounted on the bulkhead above the engine. Start by checking for loose connections or bad wires here. Then if you still haven't found anything follow the wire down to the distribution panel on the left rear wheelwell accessable thru the left side rear door where the engine breather is located, the cover is fastened on by duez 1/4 turn fasteners (sometimes the box itself is the problem witha bad ground!) Whie in there check the grounds and the posts that JohnMC9 spoke of! I'll bet by this time you'll have found the problem! If not call me at (731)885-7460) And I'll try to walk you thru some other procedures and once we locate n fix yer problem we can post it so others will have n idea what to look for if they should encounter this problem in the future! Also don't fret the remarks on the oil pressure issue some have great oil pressure and most don't! Bryce Gaston | ||
| Tim Strommen (Tim_strommen)
Rating: N/A |
Steve, It's a little late in the thread, but in the interest of getting back "on-mission", with the non-DDEC (MUI-Type) Detroit's the senders and switches that trigger these sequences are typically grounded at/to the engine. If you have the shop manual for your engine block (you should get one if you don't) you can locate each of the senders/switches that take these readings you can test them. You say the "manual temp gauge" - allow me a brief correction for the sake of accuracy - it's a "Mechanical Temp Gauge", like a mechanical pressure gauge which takes a reading and displays the value without the need for electrical power (by using the energy it's measuring to create a mechanical movement). These gauges can be wrong too, so it's a good idea to have something like a non-contact IR thermometer to point at the block. From my recollection of MUI DD 6V/8V92's, the sender isn't the mechanism that triggers a "high-temp" shutdown, but rather a temperature switch which is set at a certain point like these from Stewart Warner. When the switch (which is normally open) gets hot, it closes it's contacts connecting the wire to ground at the threaded hole it is mounted to. this will trigger a "hot engine" light and typically start a time delay until a shutdown (to avoid tripping the "engine stop" with a short temperature transient). Once this time-out is finished, the engine shutdown skinner valve will lose power and allow air pressure into the cylinder and push the fuel rack shutdown lever to "Stop". That's the basic shutdown sequence - here are the failure points for this type of system: 1) Bad temperature switch - this will remain closed no matter how cool the engine is. You can test this by removing the wire from the switch post at the block and measuring the resistance with an Ohmmeter or DMM. if the block is cool enough to touch - the measuring device should indicate an open circuit or infinite resistance. If it is showing a short or no resistance you should probably replace it... 2) Damaged Sensor Wire(s) - since the trigger signal for over-temp and low pressure will most likely be a ground connection somewhere from the back of the bus to the front. This can happen with plastic coated wires that have been exposed to fuel and other road contaminants for some time - causing the insulation to become brittle and expose parts of the wire. this can also occur when a bundle of wire (like the one going from the engine to the cab) is pressed against the frame or any other part of the structure over time - which can eventually wear off the insulation and cause one or more shorts to ground (have you had any mystery fuse blows lately?). If you have both the high-temp and low oil sensor switches disconnected, ideally the wires should show some voltage potential when the ignition is on and the engine is running (either 12 or 24 volts, depending on what voltage the sensors are wired for). If you see no resistance or a short to ground with the wires removed from the sensors, I'd remove the other end of the wires from the tell tale and/or engine shut-down timer to ensure that you don't have a short at the dash somewhere. If you remove the wires from both ends and the wire still shows a short or no resistance, then the wire is at fault. If the wire shows open circuit or infinite resistance, the wire is okay and you can focus your attention to the dash area. 3) Engine Shut-down Timer failure - I can't say for sure if your bus has one, but I'd be surprised to hear it didn't. Since the tell-tale light is showing on the dash - I'd just about rule this out - unless some wiring that goes to the shut-down timer is damaged. You say that the low oil and high temp telltales are both showing and false - both of these should start the engine shutdown timer (again if equipped), and would have wiring in the same general area. It would be worth the time to at least check this area for corrosion and/or damage. 4) Alternative Sensor Locations - Some rigs have electric gauges at the dash that output the trouble indication. These can fail, and since they are internal and typically non-serviceable, they require the gauge to be replaced. Check how your rig is wired first. Take a look at your rig and trace out the problem. Also we'd like to hear what you find so that we can close the loop on this for the sake of the archives. What ever was said earlier, I'm sorry as it sounds like it was a bit out of place. You are always welcome here and don’t hesitate to ask us more questions! Cheers! -Tim | ||
| Brian Brown (Blue_velvet)
Rating: N/A |
Excellent post, as usual, Tim. I read it this afternoon, and somehow it jinxed my bus (the new Buff), because when I went to take her back to storage, my shut-down timer is now coming on and stopping the engine. I must say that it couldn't possibly have anything to do with me messing with a relay in the elec. compt. trying to fix my tranny oil cooler fan *grin*. But I'll get it sorted out... because now I have Tim's great primer on troubleshooting it. Any headway on yours, Steve? Brian Brown Longmont, CO P8M-4108A-216 PD4106-1175 | ||
| Steve Zona (Highwayrunner)
Rating: N/A |
ON THE ROAD AGAIN.many thanks to Ace,John mc9,Bill340, and especially Bryce and Tim. I was so impressed by your knowledge and advice I printed all of this. Went out and checked each sensor one at a time. nothing there. went to the drivers side rear junction box. and removed and cleaned all GROUNDS. and low and behold .I notice the ground bar was cracked in two. leaving two sensors with intermitent ground. replaced the bar and grounds and reinstalled the sutdown swithch. and she fired right up, and stayed running. I am not absolutely positive is is completely fixed because I have not taken it on the road , but I let it run for twenty minutes and all seems great. will be driving thursday to get air leveling system overide installed. will let you know for sure. and thanks again to a great group. and yes I have "DA BOOK" Steve and Cindi 82 mc9 | ||
| Tim Strommen (Tim_strommen)
Rating: N/A |
Glad to hear we could help. Happy bussin'! Cheers! -Tim | ||
| John MC9 Rating: N/A |
Good deal on getting it fixed, Steve! Vibration and age can do as much destruction as a hammer. | ||
| H3-40 Rating: N/A |
Steve I wasn't much help due to the fact that it isn't a DDEC but I knew you would get replies that actually would steer you in the right direction! Not knowing what yours was and knowing what really happened to me, I figured what the heck! Oh well it's always good to hear of a good fix! Ace | ||
| Gus Causbie (Gusc)
Rating: N/A |
Another thing that happened to my 4104 when I first got it was very frustrating. There is a switch in the rear to be used by mechanics for an emergency shutdown if something goes wrong while working on the engine. I bumped this switch accidentally once in an RV park and didn't know it. I spent half the morning trying to solve the problem. The bus would start and run about five minutes then would stop. I read the book and found that the emergency stop required air to operste. So, what was happening was the engine ran fine until the air pressure built up enough to shut it off. Then when the air pressure dropped back down it would start immediately and then go through the same thing all over again?? I won't forget that lesson for a while! |