| Author |
Message |
Peg
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, April 28, 2006 - 7:10 pm: | |
...After a second unsuccesful attempt to get the bus started. It started right up last week, but after a weekend of heavy rain, wasn't interested. It HAS been sitting all winter. Luckily the fire was noticed immediately. It looks like this cylinder about a foot long connected by big black cables to the engine, and located behind the engine is what caught fire. We don't know what part this is yet, and if maybe wire and hose chewing sqirrels might have caused the damage. Any suggestions? |
don (Bottomacher)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, April 28, 2006 - 7:16 pm: | |
The starter? |
Peg
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, April 28, 2006 - 7:40 pm: | |
I think it could be. It's towards the top, directly behind the motor. It's long and skinny. Actually, it
looks like a stretched out version of my truck starter. It was on fire. Any one know how I can get a manual for the 4106? |
DMDave
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, April 28, 2006 - 7:50 pm: | |
Peg sounds like low voltage also. Were the batteries fully charged? If the batteries start getting weaker and the engine turns slower and slower STOP!!!!. |
Peg
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, April 28, 2006 - 9:13 pm: | |
Low voltage will start a fire? We were trickle- charging one of the batteries,which we hadn't realised was low before. |
Tim Strommen (Tim_strommen)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, April 28, 2006 - 10:29 pm: | |
Peg,
Low voltage with high current can turn a conductor (wire, coil, bus-bar) into a large resistor (read as heater).
Unfortunately, this coupled with loose connections and/or corrosion can aggravate the heating. As the heat gets higher, the resistance goes up, and so does the heat. There is a point where the heat gets high enough to soften stiff metal (like copper or aluminum) where it becomes as pliable as a licorice. This can cause positive and negative wires to touch inside something like a starter – or it can melt off the insulation from a wire (like a large starter wire) and send the limit of a wire’s current capacity to the failure point at the system voltage.
If you consider the typical 24volt starting current of a 6V92, which is slightly higher than 600 amps (YMMV) – this creates a power dissipation of 600 Amps X 24 Volts = 14.4kW of power.
I pulled a power conversion chart from this page in which they show that 1kw/hr = 3413BTU (a heat value). If you consider five seconds of cranking at this power level (across a dead short) you can create around 65,000 BTU of heat energy – this is enough to keep the entire interior of a very poorly insulated bus warm for about an hour in >>cold temperatures<<. This should easily be enough to vaporize copper and start any residual oil on fire.
Keep in mind that most small arc welders are DC low voltage and are around 2.4 kW.
Cheers!
-Tim
P.S. Everyone, please feel free to correct/validate my math – I’m just glossing over this… -T
(Message edited by Tim Strommen on April 28, 2006)
(Message edited by Tim Strommen on April 28, 2006) |
David Hartley (Drdave)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, April 29, 2006 - 6:40 am: | |
I would bet the starter is toasted
or at least the wires to it.
You cannot keep cranking on these big starters as a rule. if your engine doesn't start within 15 seconds you should wait about 10 minutes to let the starter cool down.
I didn't know that "once"... Had a fuel problem and kept cranking for 30 second blasts and after the 4th try I "smoked" a starter and started an oil fire. Nowdays I used the 10-10 rule. 10 seconds, wait 10 minutes and try again after checking all switches, fuel supplies, wires and cables if I don't get an immediate start.
3rd try, I start looking for real reasons but by that time the batteries are dead and need to be charged. This doesn't work for everyone.
Good Luck... |
Peg
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, April 29, 2006 - 6:03 pm: | |
Yep- the starter IS toast. It looks as old as the bus does, too, so it's no loss, likely. Thanks a lot for the info. We'll keep to that 10-10 rule from now on. It's good to get help from someone who has already had this happen.
Update here- my husband managed to get the starter out. Should I probably call Luke at U.S. Coach to get this part? I'm imagining it's not carried in most places. Also, can anyone tell us if there is a portable jack rated to lift a bus? It was really difficult for him to access the starter. He also said there was so much grease built up on top of the backside of the engine that he was surprised the engine could work like that at all. |
DMDave
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, April 29, 2006 - 8:06 pm: | |
Peg most altenator/starter repair shops that service heavy equipment and big trucks will be able to help you. We have a place here on LongIsland close by and there are several more in nearby towns. Its not a totaly unique to buses item, usually. It might be cheaper than paying for shipping and dealing with core charges/exchanges. Was she turning slower and slower before it toasted? better to have these problems at home than on the road. We had an altenator problem one year that really put the worry into our road trip. good luck. |
Stan
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, April 29, 2006 - 8:37 pm: | |
I have had good luck getting starters repaired or exchanged at local repair shops. With a GM bus you need to remind the man at the counter that the starter is for a left hand engine. Installing a starter on a GM and then finding out that it turns the wrong can really ruin your day. |
Frank Allen (Frank66)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, April 30, 2006 - 9:53 am: | |
Yea peg be sure it turnrs the right way, they nearly slipped me one that was wrong so be sure and ask em. had mine rebuilt at a local shop a little over 100.00 but this was several yrs ago, i dont know how your husband did the job, i had to get mine fron the bottom,
Frank Allen
4106 |
mel 4104
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, April 30, 2006 - 11:53 am: | |
Peg, one of the first things that i would do is clean all the ground connections between the starter and the battery, the one that causes the most trouble is the one on the rear bulk head. take it of and clean around it with an angle grinder with a wire brush on itand be sure to clean the terminals on the end of the cabletoo , it does not hurt to add an extra ground strap from the starter to a different location on the bulk head. i run 3 grounds -one from the engine block and 2 from the starter. - mel 4104 |
Peg
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, April 30, 2006 - 1:14 pm: | |
Thanks.
Frank- HOW did you get the starter from the bottom?
My husband almost got squashed under the bus (being foolish- jacked the bus up with a 2 1/2 ton jack and shimmied under there) and he said (and it's true) it's a good thing I'm not big. It's a good thing the ground was soft, or I'd be squished."
Ultimately his small size paid off again, because he had originally attempted to retrieve the starter from the rear access under the bed. He thought he couldn't fit down there, and he had to disconnect a couple of things to get to it, but in the end, he got down there and removed it.
I will make certain they get us the right starter.
We will also get the clean the ground connections, cables, and terminals. It's really dirty down there. He said there was literally over an inch of
build up grease/gunk on the engine back there. |
Henry van de Graaf (Hcvdg)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, April 30, 2006 - 2:33 pm: | |
Peg,
One place to get a maint, manual is on ebay.
GM Bus PD4106 Ops, Maint., Parts Manual - on CD Item number: 8061064011 |
don (Bottomacher)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, April 30, 2006 - 2:40 pm: | |
If your husband keeps messing around with 2-1/2 ton jacks you're going to be a bus widow. When he reinstalls the starter, block the bus up with foolproof blocks at the jacking points, and use a REAL jack to raise it as far as it takes to get under. Someone with the manual will be happy to fax you the page with the jack points and procedure, I'm sure. |
Brian Brown (Blue_velvet)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, April 30, 2006 - 4:29 pm: | |
Don's correct, the rear of the bus weighs about EIGHT tons... but even a rated jack can always sink into the ground or soft pavement.
IF there's enough clearance to do what you need to do under there with the bus aired up, what I do to prevent an air-down (dead man) situation is place squash blocks under each rubber bumper (the pads the bus body sits on when it airs down). You'll need about 3-1/4" of solid wood (pref. a cross-cut 4x4) or built-up steel.
Also, if you need more room under there, I prefer run-up blocks over jacks in most cases. Jacks can sink, tip, or shear (dead man situation).
Stay safe!
bb |
Steve N. (N4rsn)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, April 30, 2006 - 11:09 pm: | |
If your starter is out, it is hard to get the bus up on run-up blocks. Or to air the bus up.
When I change a starter on mine, I drop the rear engine mounts, (that the engine hangs from), and put a 21/2 ton floor jack under the engine cradle. Than I get the starter from the top. A little extra work, but I think it is safer. I am a big guy, but I can't hold up 8 tons very long |
Frank Allen (Frank66)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, May 01, 2006 - 7:44 am: | |
Peg, i jacked up the rear of the bus put a run up block under the dual wheels and crawled under, once under i had eneough room to sit up and do the job through the hole in the bulkhead, no big deal just dirty, but the jacking blocking thing needs to be done right. id rather do it that way than work from insise and get grease everywhere.
Frank Allen |