| Author | Message | ||
| Russell Beam (Rcbeam)
Registered Member Username: Rcbeam Post Number: 32 Registered: 11-2009 Posted From: 72.250.169.58  Rating: N/A |
This is my first winter for my MC8. Today was the coldest so far that I've tried to start her. Been a week since started. Low was 26, and it was 32 when I tried to start. Cranked for 15-18 seconds then sat for 15 seconds. Cranked again and started right up. White smoke while cranking but cleared immediately when started. I was very pleased. Now the problem: I left it idleing and went inside for a coffee refresh. Came back out and she had stalled. I always thought diesels don't normally stall once running. Cranked again and started right up. I increased the RPM's some (my high idle reves WAY up, so I don't use that). As soon as I took my foot off the accelerator she died. Cranked, no start. So I went to the back and found the rack in the closed position. Flipped all the switches and still closed. I was getting cold, so I turned off the batt switch and went back inside for a few. Came back out a bit later, turned on the batt switch, then the run switch, went to the back and the rack was open. Cranked and started right up and ran fine after that. Looks like maybe I have an electrical gremlin that shut it down. Coolant temp wasn't even warm yet, and oil pressure really good. Never did that before. Aside from the stalling, I'm happy with the wasy she performed during a cold start. | ||
| Dave Walker (Chrome_dome)
Registered Member Username: Chrome_dome Post Number: 122 Registered: 3-2010 Posted From: 67.174.144.159  Rating: N/A |
Russel; I always turn on the key (switch)push the start and once started (which is really quick) I flip on the high ideal switch and when it reaches 60lbs the high ideal kicks in. When it gets to 110lbs the brakes exhaust and then I can step on brake and put in gear and release the parking brake and go( that all takes 15 minutes unless I fill the system first with my shop air). When I release the brake the high ideal kicks down again. If I do not flip the high ideal switch after I start it [and then turn the key off and] just let it run, when it gets to 60 lbs. it will automatically kill the motor. but it is suppose to do that. Dave Russel re read I made a faux-pas. I added in the brackets after going out to test it and found above. Sorry my friend Dave (Message edited by chrome dome on November 07, 2010) | ||
| Russell Beam (Rcbeam)
Registered Member Username: Rcbeam Post Number: 33 Registered: 11-2009 Posted From: 72.250.169.58 Rating: N/A |
How interesting. Why does it kill the motor @ 60lbs air on regular idle? Any other MC8 guys have the same issue? This is the first time I've started the bus and it did that. I never use the high idle because it does not work right... The RPM goes really hi. The DD shop was supposed to fix that last spring when they had it for months, but evidently never did. | ||
| Debo Cox (Debo)
Registered Member Username: Debo Post Number: 32 Registered: 1-2009 Posted From: 149.168.204.10  Rating: N/A |
Hey Russell, I read that you "flipped all the switches," but wanted to make sure that the switch on the remote control box in the engine compartment is set to "run" and not "engine shutdown." (I can't remember the actual switch position names, but I think you get the idea.) I had a similar situation where the bus would crank and idle for a few minutes, then turn itself off. Once I started checking switch positions, I noticed I had shut the engine off from the rear compartment and left the switch in the "off" position. Like I said, it would crank but as soon as it built up enough air the air cylinder would actuate the engine shutdown lever. Once I flipped the switch back to the run position, it would, of course, stay running. Sorry if this is too elementary or not what you're talking about - just trying to help. Debo | ||
| Dave Walker (Chrome_dome)
Registered Member Username: Chrome_dome Post Number: 123 Registered: 3-2010 Posted From: 67.174.144.159 Rating: N/A |
Russel; re-read my last post I had to correct my miss information, Dave | ||
| Russell Beam (Rcbeam)
Registered Member Username: Rcbeam Post Number: 34 Registered: 11-2009 Posted From: 74.131.50.239 Rating: N/A |
Debo: I'll check the position of the switches on the rear panel tomorrow. I may have the one switch in the wrong position and it certainly makes sense that it would cause my problem. Dave: I am still sort of confused with what you are telling me but I'm going to check my switches tomorrow and see what it does. Thx guys for the input. | ||
| George M. Todd (George_todd)
Registered Member Username: George_todd Post Number: 1130 Registered: 8-2006 Posted From: 99.180.11.80 Rating: N/A |
Maybe an explanation of how it is all supposed to work would help! The fuel rack is actually under the valve covers, and the linkage between the governor and the heads is covered with a rubber "hose," so what I think you are referring to as the rack, is actually the engine stop lever on the governor. The engine will start and run as long as the lever is in the run position. The lever is moved to the stop position by an air cylinder, air to it is controlled by a solenoid valve known as a "Skinner" valve. On MCI buses this valve is "normally open," in other words, air flows thru it when the power to it is off. Power to the Sinnner is suplied by the master switch. Air to the Skinner valve is supplied from the auxiliary tank, which doesn't get charged until the brake tanks get over 60 lbs. These buses will start with NO air pressure, and run until the brake reservoir pressure reaches about 60 psi, and the protection valve opens. Then, if the Skinner valve has no power to it, the engine will stop. This also means that if you start the bus with no air, and shut the master switch off before reaching 60 some psi, the engine won't stop until 60 +- is reached. Whew, G | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 1938 Registered: 12-2000 Posted From: 174.89.172.98  Rating: |
Yes, George's post is correct according to Hoyle... But a lot of us have coaches that have been in the hands of heretics. The air pressure at which the engine shut down circuit will activate depends on the state of your air system and when sufficient air pressure to push the fuel shut-off closed arrives there, the condition of your pressure protection valve being critical and whether previous owners have been "customizing" the air plumbing. There is no commonly performed check of the air system to confirm the pressure protection valve's functioning, and it's functionality is not referred to specifically in DOT requirements. Also, as a matter of preventive maintenance, changing out the switches in the rear panel with new ones eliminates a common source of intermittent gremlin. The original switches were sealed at the shafts to slow the contamination, so feel good about buying good ones! The previous owner may have installed common switches (cheaper than sealed ones) that will be corroded inside. happy coaching! buswarrior | ||
| Russell Beam (Rcbeam)
Registered Member Username: Rcbeam Post Number: 35 Registered: 11-2009 Posted From: 74.131.50.239 Rating: N/A |
After understanding the switches on the rear panel I'll try it again this weekend and see what happens. Understanding how all of this ties together helps. Thx guys for the explanations. |
