Stuck Jakes??

Nick Badame Refrig/ACC · April 13, 2010, 03:50:52 AM

Hi Guy's,

On our way home last week from VA Beach, I noticed a huge lack of power during a lane change.

I looked in my mirror and saw black smoke when I pushed the throttle and the power wasn't there

at all. I also noticed my coolant temp almost at overheat... I pulled over and left the engine at idol

in hope to cool the DD down. It did cool pretty fast and idoled normally. ??

I then proceeded to take off again to see what happens. It did it again... The engine sputtered with

black smoke.

Then it hit me, "JAKES R ON" I reached to my jake switch and turned them off. WALA.. all normal now...

OK, what should I point to first? Buffer switch? I guess they fail... It's 2 years old??

Thanks
Nick-

bevans6 · April 13, 2010, 05:05:14 AM

When your Jake switch is on, everything is basically under the control of the buffer switch so that's where I would look first. The test procedure in my manual is jake switch on, power to the buffer switch, no power to the solenoid side of the switch. Idle the engine, same thing, power to the switch and no power to the solenoid side. Snap the speed lever to full throttle, engine rev's up, snap throttle off, power to the solenoids and hear the exhaust rattle as the engine speed returns to idle. Engine may stall.

Brian

JackConrad · April 13, 2010, 05:27:03 AM

Nick,
Might be as simple as the buffer switch is out of adjustment (maybe locknut loosened?). I agree, that would be the first place I would check. Jack

white-eagle · April 13, 2010, 06:02:13 AM

as you all know, i'm no expert at this stuff, but when my buffer switch needed replaced last summer, i experimented with the adjustment. if i screwed it in too far, the engine would bog down at idle. loosen it up and no jakes. i suspect something came loose and just needs an adjustment on yours. that would be the best bet and certainly the least expensive.

i also was doing this just becuase my original buffer switch had failed and was superseded by a better model. if yours was the original, then you may also need to look at getting the upgraded, newer switch.

i can probably find the invoice if you find you need a part number. i think it was about $120.

luvrbus · April 13, 2010, 06:31:11 AM

Nick, do you have a fast idle buffer switch, with all Jake buffer switches take care when trying to adjust if you screw the switch in just a little to much it won't stop the engine it will run away fwiw

good luck

Merlin · April 13, 2010, 02:17:11 PM

I wish to show my total ignorance on this subject. Where is the "buffer switch" located? I may need to find it since I think my Jake is inop. Worked super until last week ... then zip ... it does nothing now.

JackConrad · April 13, 2010, 04:18:15 PM

On an non DDEC engine, it is located on the governor screwed into the side of the governor with a couple wires connected to it. It they are not operating at all, start by checking for power through the dash switch to the buffer switch. Jack

PP · April 13, 2010, 06:49:00 PM

This is like too wierd! The same thing happened to me going north on 101 about 2 weeks ago. I was coming down a grade and when I accelerated at the bottom I had no power. I didn't notice an smoke however till I switched off the jake and then just one big cloud and a surge of power. (TG) I haven't had time to look into it since, so I've just been using the jake switch as needed. The fuel guage also went from 3/4 to empty on the same trip, go figure LOL. I've since filled her to the brim and she still shows empty. At least it wasn't dumping fuel on the highway. I can live without a working guage since I always go by miles on the odometer between fills anyway. Will

NewbeeMC9 · April 13, 2010, 07:04:23 PM

Quote from: PP on April 13, 2010, 06:49:00 PM
This is like too wierd! The same thing happened to me going north on 101 about 2 weeks ago. I was coming down a grade and when I accelerated at the bottom I had no power. I didn't notice an smoke however till I switched off the jake and then just one big cloud and a surge of power. (TG) I haven't had time to look into it since, so I've just been using the jake switch as needed. The fuel guage also went from 3/4 to empty on the same trip, go figure LOL. I've since filled her to the brim and she still shows empty. At least it wasn't dumping fuel on the highway. I can live without a working guage since I always go by miles on the odometer between fills anyway. Will

Mercury is in retrograde

Nick Badame Refrig/ACC · April 13, 2010, 07:54:50 PM

Hi Guy's,

Whenever I plan time for myself, "to work on my bus" something always seems to come up!!!

So, I didn't get to work on it at all today. Maybe tomorrow..

My buffer switch is two years old and it came new from my detroit dealer. Almost $600 bucks...

It is also my fast idol and I have a non ddec engine.

Nick-

bobofthenorth · April 15, 2010, 10:48:49 AM

I guess I've been lucky that my buffer switch has lasted for several years. I don't have the combined high idle/buffer switch arrangement that is so expensive. I like mine set so that the engine occasionally stumbles when it's idling with the jakes on but as others have warned, be really careful about setting the buffer because the difference between strong jakes and a runaway can be less than one adjusting turn.

The last time I set mine I had trouble getting the switch to consistently turn on without having it screwed in so tight that it scared me (you can hear the RPM's start to come up when you get into the danger zone). I finally ended up carefully pruning one coil off the spring on the buffer switch with a very small set of side cutters. That reduced the necessary pressure to activate the buffer switch enough to let me set it a little looser while still getting the activation I was looking for. YMMV.