throttle stuck temporarily
 

throttle stuck temporarily

Started by napamikey, August 20, 2014, 02:11:35 PM

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napamikey

Hey guys. Heading up 80 to Reno and I had it floored going up steep hill, let go of throttle and it remained engaged. Stepped on gas a few times and loosened up. It only happen once. Temp fine, oil fine. Jake brake also worked. Could this be a stuck throttle cable or something worse? Does the cable just need to be lubed?
Scary!
Thanks for help, radiators and coolant are fine!
1967 MCI 5a 8v71
San Francisco, CA

gumpy

Could be as simple as the hinge points on the foot pedal. Spray that first. If that doesn't free it, start following the linkages, lubricating everything that moves (or is supposed to move).
Craig Shepard
Located in Minnesquito

http://bus.gumpydog.com - "Some Assembly Required"

pabusnut

Mine stuck too, but not that bad.  It wouldn't quite return to idle, and that along with a couple other items, my inspection shop wouldn't put a sticker on it.

I pulled the whole 40+ ft cable,  and cleaned it with a wire wheel on the grinder.  I then pumped some "sneaky pete" through the tube to the front(yea, I know the stuff has been outlawed for years), and let it sit for a couple of days. Then I blew that out(what a huge mess) and put the cable back in, after I lubed it up good with water resistant lithium grease.  It was almost as tough getting it back in as it was pulling it out w/ vise grips.  Based on the resistance I felt, I thought there is no way it even feels bettter, but after I got the springs hooked up both at the front and back, it works really smooth with little foot pressure.  I also pulled the pedal at the floor, and gave it a little more clearance on both sides between the pedal and the base right at the pin, and lubed that up good too.  Well worth the work.

Steve Toomey
PAbusnut
Steve Toomey
PAbusnut

TomC

This is where the nice light pedal pressure of an air throttle comes in. Good Luck, TomC
Tom & Donna Christman. 1985 Kenworth 40ft Super C with garage. '77 AMGeneral 10240B; 8V-71TATAIC V730.

chessie4905

   The "sneaky pete" I remember was a rear main seal remover. (rope style)
GMC h8h 649#028 (4905)
Pennsylvania-central

pabusnut

"Sneaky Pete" was a penetrating oil, back before the days of msds's for safety and environmental compliance.  My Grandpa had a case or two still left in his garage when he passed away 11 years ago, and I think I still have a few cans in my garage. 

Steve Toomey
PAbusnut
Steve Toomey
PAbusnut

bevans6

My MCI has a teflon lined Belden type cable, not like the GM's where it's a cable inside a tube.  It is fed through a few dozen small holes in bulkheads all down the center of the bus.  If you pull it out, pull a cord through after it or you will never get it back in.  Check the ends of the cable where the steel core comes out of the sheath, mine was very frayed and worn.  Since it's a teflon lined cable it can't really be lubed, if it is sticking you have to replace it.  I got a new one made up by a place that services aircraft, and the ends were too big to fit through the holes (.515" diameter, and one of the holes was .505" - 10 thou too big is still too big...) and I ended up cutting off one of the ends, pulling it through, and putting the end on again.  Have fun with it, I did...   ::)

Brian
1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
Allison MT-647
Tatamagouche, Nova Scotia

brmax

Guys the hinge point on different pedals was a nightmare with salt and calcium from boots, that's what it takes and a lot of it to clear or provide a path on the highways. As mentioned cables can fray, my luck with them were small or sharp turns in the cable but mostly the hinge corrosion. lots of towels and penetrating oil
Good day
1992 MC9
6V92
Allison

napamikey

Thanks for all of your replies, I finished the journey with no additional throttle problems but it was scary.  After some thought I think this was caused by something stuck in the engine at full throttle and not the peddle.  The reason I think this is due to the Jake still engaging even though it was at full throttle.  It disengaged when I pressed the peddle down and after a couple of floor pushes it all seemed to be fine.  I did not floor it for the rest of the journey.  I do think it is a good idea to check out the cables though.
1967 MCI 5a 8v71
San Francisco, CA

gumpy

Did you check your return springs on your throttle linkage on the engine?
Craig Shepard
Located in Minnesquito

http://bus.gumpydog.com - "Some Assembly Required"

luvrbus

More than likely you have the old micro type Jake switch and and the pin stuck,the buffer or one or both of the 2 springs on the linkage inside the governor came off and wedged the linkage that is about all that would cause it I see it all the time the springs missing and the old DD hunting for a spot does your surge now when it 1st starts ?

 
Life is short drink the good wine first

Dave5Cs

Mikey did you get any damage from the earthquake?
"Perfect Frequency"1979 MCI MC5Cs 6V-71,644MT Allison.
2001 Jeep Cherokee Sport 60th Anniversary edition.
1998 Jeep TJ ,(Gone)
Somewhere in the USA fulltiming.

napamikey

I had no damage from the quake, but I hear a lot of wine went down the drain. Damage was mainly limited to the bouncing clearing out the cupboards and bookshelves.  It's amazing how much things can move in such short time!

I checked the back and everything seemed ok.  When the bus does start it does hunt at idle until it "warms up" and then idles fine. Sometimes 30-45 seconds. I usually just press the gas to give it a "fast idle".  I think something stuck when I had the pedal to the metal going up a hill. I will check out all of your suggestions.

Thanks again!
1967 MCI 5a 8v71
San Francisco, CA

lvmci

Hi Mikey, I cant push my accelerator pedal down during hi idle, Clifford, is that the way it is supposed to be? Hi idle wont engage til 40 to 60 pounds of air pressure, on my 66 5A, Tom lvmci...
MCI 102C3 8V92, Allison HT740
Formally MCI5A 8V71 Allison MT643
Brandon has really got it going!

Dave5Cs

Tom Yep,

Napamikey, Sometime if you are pushing to the floor up hill back off a little, It isn't like a gas engine. It won't go fast at a point it will only burn more fuel or actually past it through because it can't burn anymore.

MY sister got about the same she live of Jefferson toward Trancus end. She had a lot of old china and cabinets in the kitchen all came down. Stuff everywhere and a big crack in the plaster out front that wasn't there before the quake. She won't sleep upstairs. Shes affraid now of getting trapped because their back door was jambed and they couldn't get out.
"Perfect Frequency"1979 MCI MC5Cs 6V-71,644MT Allison.
2001 Jeep Cherokee Sport 60th Anniversary edition.
1998 Jeep TJ ,(Gone)
Somewhere in the USA fulltiming.