| Author |
Message |
jj-mc9
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, April 29, 2005 - 8:19 pm: | |
I have an MC9 with a 6V92T and allison 4 speed. The couple times this week I put it in reverse and touched the pedal to back out of the shed, the engine raced and the tach went up to around 1500 rpm. If I put it in neutral, the engine speed returned to normal in 5 to 8 seconds. It doesn't seem to do that once the engine's warmed up.
Any thoughts on what might be causing this? One mechanic at a Freightliner shop thought the injectors.
A novice thanks you for the advice. |
Geoff (Geoff)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, April 29, 2005 - 8:38 pm: | |
I assume you have mechanical injectors (not DDEC), so the problem is something sticking in the linkage. The only way to find the problem is to start at the governor and through inspection and testing find the problem. You need to take you bus to a Detroit 2-stroke mechanic that is familiar with these engines. The easiest place to find a good Detroit mechanic anymore is a charter bus company.
Where are you?, perhaps someone can give you a recommendation.
Good luck!
--Geoff
'82 RTS CA |
TWODOGS (Twodogs)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, April 29, 2005 - 8:40 pm: | |
a seal on the govenor ?? |
John that newguy
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, April 29, 2005 - 9:04 pm: | |
Hmm...
An air throttle? It doesn't do that after it's "warmed up", or
after it's fully aired up? Trying to move the bus before it's
fully aired can result in all sorts of peculiar happenings, especially
when an air throttle's involved. |
jj-mc9
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, April 29, 2005 - 9:20 pm: | |
I'll try to find a mechanic familiar with 2 cycle detroits. In the Omaha area, there should be some. I'll also ask an area charter company for referrals.
Nope...not an air throttle. Didn't have this "sticking" problem until this week. A plate near the driver sez to let the air gauge reach 100 or more before trying to move, which I do. Looking forward to when I have more camping time than shop time. |
John that newguy
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, April 29, 2005 - 9:31 pm: | |
Hey, out of curiosity, are you turning off the fast idle before moving
it, or leaving the switch on, and letting the interlocks disengage it?
(Don't mean to assume anything on your part, but I've always had
a habit of looking for the simple things first) |
Buswarrior (Buswarrior)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, April 29, 2005 - 9:46 pm: | |
Hello jj-MC9
If your engine is running eratically, this may indicate a VERY serious problem which you cannot treat lightly or ignore.
Your engine is not running under proper control. Consequences of your engine losing complete control is that it will speed up to higher RPM until something breaks, sometimes involving flying parts.
If you have mechanical injectors, do you have an engine emergency stop device, does it work, and do you know how to use it, if the engine begins to race uncontrolably?
I would suggest that you not run the engine again until you are sure you know how to stop it if it runs away. Find a busnut or DD mechanic near you to help out. Lots better to be embarressed than to risk blowing up your engine.
There are no shortcuts to the maintenance of the engine governor and all of the fuel delivery rack. You MUST identify what is binding, sticking,hanging up, and replace what's worn, broken or bent. Freeing it up isn't good enough, whatever led to the problem will re-occur.
Anyone who tries to save money by stretching the useful life of fuel rack parts is courting an expensive disaster.
The costs associated with the premature loss of an engine is usually the end of the busnut dream.
Please do not be embarressed to ask us some more questions, better than the $$$ involved in learning the hard way!!!!
Lots of good folks here to offer sound advice.
happy coaching!
buswarrior |
Luke Bonagura (Lukeatuscoach)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, April 29, 2005 - 9:53 pm: | |
Hi JJ:
Good info. & sugestions from our fellow bus-nuts, but I have a question.
How long was the coach in the shed???
If stored for an extended period of time, it could be that you have rust built up on the pin that your accelerator pedal pivots on.
Best way to check is to start it up again "COLD" and if the engine races, pull the back of the pedal up with you tow or your hand.
If it stops racing, you found the cause of your problem, without the need for a mechanic.
We store coaches on our property for numerous large commercial ventures, and we find this is a common problem after they sit for a while.
A couple of squirts of WD-40 and the pedal frees up and off the coach goes. And by the way, for others, it also occurs with the Brake Pedal.
These Coaches were built to operate, not to sit for extended periods of time, and the longer they sit, the more problems an owner may expect!!!!
I Hope this HELPS!!!
Happy & SAFE Bussin' to ALL.
LUKE at US COACH |
Buswarrior (Buswarrior)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, April 29, 2005 - 10:04 pm: | |
All bow LOW, on your knees!!!!!
before Luke, the bus guru.
He knows all the tricks, and then some!
happy coaching!
buswarrior |
jj-mc9
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, April 29, 2005 - 11:16 pm: | |
Replying to Luke, I try to take the bus out for some miles every seven to 10 days. It's loads of fun just to drive, so the camping part will be icing on the cake. Taking out a loan just to buy fuel is a downer, though.
10-4 on turning off fast idle before releasing the brake, john. Will also try the WD on the two pedals when I'm working on the bus on Saturday.
Appreciate all the help, guys. |
RandySteere
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, April 30, 2005 - 11:29 am: | |
JJ,
If you are using the fast idle to warm the bus up make sure the plunger on the solenoid is releasing all the way when you turn it of. They will often get gummed up and stick partially in the on postion. This will not allow the engine to idle down. |
Peter E (Sdibaja)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, April 30, 2005 - 12:55 pm: | |
Luke is 100% on the money, happens with air throttle too. Yes, it is scary! |
Jim (Jim_in_california)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, April 30, 2005 - 3:45 pm: | |
If the engine is racing, doesn't it need the rest of the vehicle to have any chance at winning? |
jj-mc9
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, April 30, 2005 - 8:01 pm: | |
Naw Jim...when the engine is racing, the rest of us are just small potatoes, or speck tators. |