| Author |
Message |
philip potter
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, March 26, 2005 - 8:39 pm: | |
OK, we are close to the end of a long project, at least for me...installing a 6V92 and 748 Allison in my MC8.
We started her up and she doesn't want to run below 1,800 rpm's. The stop lever works fine.
It has a mechanical governor. When we take to top cover off the governor, we can control the speed/idle fine. There is no binding of the fuel rods, everything moves freely. The weights move freely as well and everything seems to be in order. We put the governor top plate back on and she won't idle down. The top plate was from the old 8V71 that came out of the bus (to match the thottle rod) so we changed and put the origional back on. It does the same thing. The cover is on properly and the pins are lined up(inside and out). The speed control lever can't be moved far enough for it to idle down.
I know there is an idle adjustment, but I can't help but think we are missing something. Certainly this engine didn't idle at 1,800 rpm's when it came out of it's donnor. What happened? Is there something I am overlooking? |
Brian (Bigbusguy)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, March 26, 2005 - 8:43 pm: | |
Fast idle air hooked up wrong? |
philip potter
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, March 26, 2005 - 9:12 pm: | |
Ok, here is where I am confused. I believe the governor on the 8v71 only had air hooked up for the shut off. Educate me where I'm wrong please. SO I don't have any air hooked up to this 6v92. The origional top plate to the 6v92 had an extra plate on top of it that had air components on it. I don't understand these. This must be where my ploblem is. Can you please explain how this works and what the function of the air components are? My Detroit service manual doesn't do a good job of helping me here.
I thought, if I could understand this statement (the only thing that I have found talking about air in connection to the governor)from the manual, I might solve my problem...."The removal of air pressure from behind the piston permits the governor high-speed spring to force the piston against the low maximum speed adjusting screw that retains enough tension in the governor high-speed spring to operate the engine at the desired lower speed" ...but I don't have any air presure on it to remove at this point.
please help. |
John that newguy
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, March 26, 2005 - 9:37 pm: | |
Yikes!
You solved your own problem!
To wit:
"removal of air pressure from behind the piston permits the
governor high-speed spring to force the piston against the low
maximum speed adjusting screw that retains enough tension in the
governor high-speed spring to operate the engine at the desired
lower speed" ...but I don't have any air pressure on it to remove "
(No air = no air)
Sounds like you're missing a few components to the assembly, eh?
Re:
"The top plate was from the old 8V71 that came out of the bus (to
match the throttle rod) "
I don't know much, but I wouldn't try to "mix and match" that assembly.
Isn't there a truck garage with some spare, used parts for you? |
philip potter
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, March 26, 2005 - 9:56 pm: | |
I think it is more the issue of using the origional govenor cover with it's air components connecting to the speed control and figureing out what they are and what they do. I have a mechanical throttle rod on my bus. I, at first thought, this air stuff might have been to some type of air throttle control instead of a mechanical throttle rod and was hoping on changing it over.. oh well.
so, can anyone help about this air stuff connecting to the governor? |
philip potter
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, March 26, 2005 - 10:25 pm: | |
The quest goes on... the comment from the manual about "removal of air pressure", etc refers to a Dual Range Governor. It looks like I have a Standard Double-Weight Governor. I still don't know what an air piston type of assembly hooked to the speed control lever has to do with this thing. It does not show up in my 92 series service manual. |
jimmci9 #@
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, March 26, 2005 - 10:41 pm: | |
governor covers are the same, regardless of what type of governor you have... in place of the buffer screw, there MAY be another cylinder that is the air-operated high idle...this cylinder has a moveable tip (like the buffer screw) and may be causing your high rpm's.... normal hi idle is in the 1000-1200 rpm range.... |
John that newguy
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, March 27, 2005 - 7:40 am: | |
On my 6v92, I have an air throttle. On the top of the plate
there are three air selenoids.. The acellerator, the shutdown
and the high idle. A (big) picture is here:
http://www.dialup4less.com/~aabn/throttle.jpg
See if yours is the same?
(where are the experts when you need 'em?) |
philip potter
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, March 27, 2005 - 12:15 pm: | |
I think it may be simalar. The air components were fastened to a separate plate that was attached to the top plate of the governor. It had an air cylinder attached to the speed control lever. I'll have to take another look at it, but I think it had another one to the shut off lever just like my old 8v71 set up.
The only air was set up to speed control and stop levers. No air control in place of the buffer scew. |
philip potter
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, March 27, 2005 - 12:18 pm: | |
by the way, how do you do the posting a web address with a picture thing? that would be handy at times. thanks for taking the time to do it. |
John that newguy
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, March 27, 2005 - 1:39 pm: | |
I couldn't find adjustment details for the air control model on mine,
but I'm still looking. When I first got the bus, the air solenoid on
the bottom left (in that picture) was loose. So without a manual
to guide, I tightened the control into the base as far as it'd go
and tightened the locknut. When I fired up the engine, it went
full bore, wide open... YEAOOOOW. Man, it wouldn't shut
down and my intake doesn't have an emergency shutdown
flapper... I had to reach in between the belts with the engine
going full tilt, and loosen that air solenoid, slowing down the
engine and permitting me to shut it off.... whew. Don't do that!
On the pictures? Your ISP should provide a "home page" that
you can upload pictures, etc to. Just past the URL into the
form here when you post and I@n's system will add the html
code to produce a working link.... Use the full URL, as in:
http://www.dialup4less.com/~aabn/MC9_docs/
One of these days I'll update that page. I had wanted to add
usable data for MC9s on a weekly basis...
ya'll know how that goes.. |
Jtng
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, March 27, 2005 - 1:42 pm: | |
Oh.... for the picture (or any file) just add include the file's
name in the url.... blah.com/filename.gif |
Brian (Bigbusguy)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, March 27, 2005 - 3:59 pm: | |
Http://www.blah.com |
John that newguy
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, March 27, 2005 - 8:23 pm: | |
Har!!
Si. mucho gracious |
Geoff (Geoff)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, March 27, 2005 - 9:12 pm: | |
The high rpms are probably from misadjusted governor control levers. The way to test this is to loosen or simply remove the speed lever from the governor top and run the engine with a pair of vice grips on the large lever shaft. If the engine idles down then simply adjust the throttle and stop levers so you get full travel at the governor levers. It doesn't take much to run the engine up if they are adjusted wrong. And if this isn't the problem, then you probably have a problem with the rack adjustment or it is binding inside somewhere.
--Geoff
'82 RTS CA |
John that newguy
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, March 27, 2005 - 9:58 pm: | |
Hey Phil-
Did I understand you right? You're trying to use an air throttle
assembly with a mechanical accelerator?
If so, why not get the rest of the air throttle stuff and do it total air?
I wouldn't go tearing into the rack... hell, you did say it starts
right up and it's running good... |
philip potter
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, March 28, 2005 - 8:30 am: | |
The bus it's going into is a mechanical throttle, so I'm just taking of the top plate of the governor and replacing it with the top plate from my old engine to match up to the mechanical throtle.
either way, the bus runs the same with either plate on. Today, I'll be looking for something that causes it to bind when the top plate of the governor is placed on. |
R. Steve Nichol (N4rsn)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, March 28, 2005 - 9:28 pm: | |
See if your buffer screw is tightened down to far. It can be holding the throttle down a small amount.
Check for binding in the linkages.
Any time I work on a governor, or anything concerning the racks, I remove a valve cover, and clip a pair of vice grips on the rack, so if things get out of hand, I have complete manual controll of the throttle.
Just a thought
Steve |
philip potter
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, March 28, 2005 - 11:50 pm: | |
If the buffer scew was the problem, wouldn't it still have the same problem when we take the governor cover off?
new items to add to this problem:
1. I noticed that the weights have a little bit of slop before they hit the spring, 1/8 - 3/16".
the old 8v71 still sitting in the shop is tight. How would this affect things?
2. we run her up to about half throttle and the governor doesn't hold her there. She still wants to run up a few more 100 rpm's while we are holding the throttle still. The weights don't seem to be pushing back to maintain rpm's |
Geoff (Geoff)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, March 29, 2005 - 7:05 am: | |
The buffer screw could very well be your problem if you moved it when you did the installation. Taking the gov top off does not affect the buffer, you need to back it off. Annyway, doing all these adjustments is very risky-- you may end up with a runaway engine. I worry about novices messing with the rack and governor adjustments for this reason.
--Geoff |
John that newguy
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, March 29, 2005 - 7:50 am: | |
Phil-
It's tough trying to fix anything without a manual.
There appears to be big differences between the manual setup
and the air one. The adjustments are different also, since
one doesn't rely on an air solenoid to push the fast idle back.
I almost scanned the pages out of the DD manual for you,
but man..... After looking at it all, I'd have to do 1/2 the book!
I think you'd be best using the entire assembly and not try
to put a manual control cover on an air assembly.
In any event, make sure your emergency stop works. You may
blow a few seals, but it'd be better than picking DD parts
out of the neighbor's walls.. |
R. Steve Nichol (N4rsn)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, March 29, 2005 - 3:22 pm: | |
Well I see the last post was at 7:50 this morning, and it is a few hours after that now, so HOW, did it go, after the buffer screw was backed,(about 1/2") out???
Don't worry about the weights, and the space in the weights. The buffer screw will take the slack out of them. The buffer screw has a small spring in the end, and all it is suppose to do in take the (Roll,as it is called) out of the engine.(the roll is when you suddenly accelerate, and drop back to an idle, the buffer will not allow the engine to idle fast, than slow, than fast than slow, ect.
If you back the buffer out, it should come to an idle. If it don't.!!! PLEASE" get a mechanic, that knows about 2 cycle DD's, as the governor is the brain of the engine, and 1 mistake, and it can be serious.!!!! I can't stress this enough!
If the engine comes to an idle, screw the buffer back in< "Slowwwly" untill the engine starts to come off idle. Than back it back about 1/2 turn. now accelerate the engine, and let it drop immediately back to an idle. If you get a "roll" in the engine, screw it in about 1/4 of a turn. It should be out, and ready to go, as soon as you tighten the locknut to hold it in place. |
R. Steve Nichol (N4rsn)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, March 29, 2005 - 9:12 pm: | |
I guess he is still picking up parts, or he got it fixed, and is out riding. I hope he is riding
steve |
philip potter
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, March 29, 2005 - 11:04 pm: | |
Thanks, but it isn't the buffer screw.
The mechanic has the full set of manuals on 6v92's. He just got done rebuilding one last fall.
Tinkering with the governor is his last resort. If it works, leave it alone. He found,however, what appears to be a bad bearing in the governor. We have one ordered, coming in two days. I'll be gone over spring break. Hopefully he'll have her running right when I get back on the 9th. I'll let you know what happens.
thanks for the input of all |
Geoff (Geoff)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, March 30, 2005 - 7:31 am: | |
He has a set a manuals and rebuilt one engine? If the governor worked in the other bus and now it idles fast then you need someone who really knows Detroits to take a look at the rack and governor adjustments. I hope he doesn't think the riser bearing is bad-- it is a 3-piece bearing and supposed to be loose. Can't you find a real Detroit mechanic to look at your bus?
Where are you located? |
guy 4905
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, March 30, 2005 - 7:14 pm: | |
The actuating distance on the different cover is most likely not the same as the one that was on your motor. You will most likely have to readjust your fuel rod settings to restablish the correct lever distance,
Guy 4905 |