Fast Idle Buffer switch position?

[Timkar]

Always had trouble with my fast idle and now that I have drained coolant and moved rad (rear rad) I can access the area. I found that the diode was no longer operational. Got new diode and installing switch back in position. The switch mounts on a set of "tracks" and can be tightened in a position where the switch is open or closed. This is a normally open switch and when it is activated the contacts close. When the bus is sitting with nothing on or running what position should this switch be in? (I am guessing open) Just want to be sure because when I refit rad and fill with coolant I can longer access this area. The fan at the rear is great for cooling but a PITA for maintenance.
Should have mentioned 8V71T...
TIA....Tim

 

[luvrbus]

It installs in the open position you want me to send you 10ft of GX wire to replace the white stuff

[Timkar]

Thanks Clifford....Do you have a link to the specs for the GX wire? I may have some here...

[bevans6]

My understanding of the buffer switch operation, and I just walked out back to check on my engine, is that the buffer switch will be closed when the governor is in no-fuel, and open any other time.  On my engine it goes to no-fuel when the engine is running and it's on over-run, which is what you would expect, and it also goes to no-fuel when the no-fuel lever is operated.  On my bus that lever is closed normally but opens when the engine is shut down with the skinner valve, and it stays open with the engine off as long as there is air pressure available to it.  So I would say that you need to double check the position of the engine stop lever to know if the buffer switch would be open or closed with the engine off.

Brian

[luvrbus]

I always get closed and open mix up that is the reason I never give electrical advice it has to be closed in the no fuel for the Jakes to be activated.

Find one of Geoff's old post here or at the BNO he is the best at adjusting those for rpm and smooth operation I ever seen on the combo switch   

[Timkar]

Now I'm getting a bit (more) confused.
I have just aired the bus up and the activating "lever" stays in the same position with or without air and the key on or off.
I cannot start bus as I have no coolant in it at present.
Brian...when yours is sitting with no air, etc what position is the switch in? closed?

[luvrbus]

The only time you have complete no fuel is with the shut down,I am getting confused also the switch has to be closed at idle and open under throttle the best I can explain it 
What problems are you having the diode is not going fix anything pull a valve cover off and see if somebody installed condensers on each solenoid if they did remove them and toss those in the trash


good luck 

[bevans6]

When my bus has no air the engine stop system is inoperative, the air cylinder push rod is retracted, the no-fuel lever on the governor is open and the buffer switch is open electrically.  When my bus has air and the front master switch is off, the air cylinder push rod is extended and the governor is in no-fuel.  When my bus has air and the front master switch is on, the air cylinder push rod is retracted and the governor is not in no-fuel.  If I then operate the rear control switch engine run/off to off, the push rod extends and the governor goes to no fuel.

The simple way to understand this is to understand how the buffer switch works in the first place.  It has a rod that extends into the governor and is operated by the idle control of the engine.  That idle control pushes on the switch rod in only one condition - when the engine is in no fuel.  The engine can be placed into no-fuel manually using the lever on top of the governor, or it can place itself into no fuel whenever the engine is in over-run - no throttle applied and the engine is decelerating.  That no-fuel condition is the only thing that can press on that switch rod and close the switch.  Closing the switch allows electricity to flow to the jake solenoids and apply the jakes, if the engine is running.  If the engine is idling, it just stops so the jakes never have time to apply, even if they had sufficient oil pressure to work.

I can test my buffer switch by simply moving the lever to no-fuel, and the switch closes just as the lever gets all the way to it's stop.  When I was first tuning my engine after I installed it my jakes didn't work.  I had to re-adjust the buffer farther in so that it had more control of the idle, and then the buffer switch started to work.

So the simple thing for you to do is to install your switch and turn the no-fuel lever all the way.  Just at the end of it's movement you should see the buffer switch close (actually I can hear mine click if the engine isn't running, I can't see it operate unless I have a test light on it).  Now - have you moved the buffer control at all (the 3/8" threaded rod that sticks out of the side of the governor that the buffer switch mounts on to)?  If you have, you need to fully adjust the buffer control after you start the engine and before you start to worry about the buffer switch working or not.  It's adjustment is first and foremost critical to the idle control of the engine, and it can make the engine run away if it's adjusted too far wrong, and is only secondarily critical to the operation of the jake buffer switch.

If not clear, ask more questions!  I am trying to avoid going outside and chipping up a bunch of branches I cut down.

Brian

[bevans6]

Clifford, the switch has to be open while running, open at idle and only closed on over-run if the engine is running.  Over-run is when the engine is at speed, the throttle lever is fully closed and the engine is decelerating, is the best way I can describe it.  If the jake switch was closed at idle the engine would stall.

Brian

[luvrbus]

I can't explain this stuff if it was here I could fix it in 5 minutes

[Timkar]

Took of some exhaust pipe and was able to access air cylinders.
The plungers were all covered in years of grime. Cleaned these up and now
I have a difference between key on/key off. When the key is off the switch would be
closed and when the key is on the switch is open. Sounds as though this is what I should
have. Please correct me if I am wrong.
The system is aired externally. The "lever" moves approx 1/8-1/4" between key on/key off  

[bevans6]

That is the buffer switch push-rod that I was talking about.  That is hung off the side of governor.  On the top face of the governor there are two levers, one is the throttle lever and the other one is the engine stop lever, what I have been calling the no-fuel lever.  If you have the engine off and no air pressure you should be able to move the engine stop lever about a 1/8th turn with your hand, easy.  It moves clockwise.  Your other lever, the one in the picture, should move a bit right at the end of the travel of when you rotate the engine stop lever, showing that your buffer switch will close right as the governor gets put into no-fuel.

What bus is that engine in?

Brian

[Timkar]

Engine is an 8V71T  The way I have set it now is that as it sits with nothing on, no air, the switch is closed.
The switch opens as soon as I air and put power on. When I rotate "stop lever" clockwise the switch closes again

[bevans6]

Looks right and proper to me!  Closed when it's in no-fuel (top picture, air cylinder extended) and open when it's in engine on, ready to run mode - bottom picture. 

Brian

[Timkar]

Thanks guys...Now I can put the rad back in and get it running
PS   the electrical fan in pic is for when gen set is running....