More diagnosing

[Blacksheep]

Checking out my Jakes which have never worked we found some PO wiring that was a lot to be desired so after downloading the schematic and fixing it the correct way, we still can't get them to activate. Voltage at the relay and using the switch on the dash changes to zero voltage. My question is, would the Jakes work if the parking brake is NOT released? I was thinking that maybe the mechanic didn't release the parking brake and that's why they won't work.
Thanks...
Ace

[JackConrad]

Ace,
   I don't think the Jakes will work unless the bus is moving and the throttle is at idle position. This was 2 requiremnts for every Jake equipped bus I have driven. I don't think this can happen with parking brake on. 

[Blacksheep]

Jack being electronic we can check it via the pro-link without the bus actually moving. My question was to mean would they work with the parking brake applied? I say probably not since the brakes are already applied! We will try releasing the parking brake and try activating the jakes again. Hopefully that is all we missed on Friday at closing!
Ace

[JackConrad]

OOPs, I keep forgettin' my engine is a dinosaur LOL.  I have driven 2 series 60 equiped buses with Jakes, but both were being driven, when Jakes were activated.  I did not know thy could be checked with the ProLink.  Jack

[VanTare]

On a DDEC  the Jake's works through a module check your grounds the green and the yellow wires they should have a separate ground from any other grounds and if you do not have abs brakes the orange wire should be insulated from other wires.check all the wiring harness and where it plugs into the ECM. electronic controls are fun   


David

[Blacksheep]

David, already checked connections and grounds. Only thing was we tried to activate them but forgot about parking brake was still on! Our mistake! That was why I asked if the parking brake HAD to be released which in my thinking, it does!

Ace

[VanTare]

Ace if your fast idle is tied into the parking brake you are right they will not activate.Can you down load 1.1.23 of the Jakes book if not maybe I can email it to you  hope I got it right this time 

David

[RJ]

Ace -

Not sure on the electronic engines, but IIRC on the MUIs, the jake is also interconnected to the fast idle - it won't work if the fast idle is on.  And, as you probably know, the fast idle is interconnected to the parking brakes - the fast idle will not work if the parking brake is released.

Based on all that, if the parking brake is on, and the fast idle is on, the jakes will not work.

OTOH, if the parking brake is on and the fast idle is off, the jakes should work.

DDEC's may be similar, but not sure.

FWIW & HTH. . .

[rv_safetyman]

Ace, I don't have my DDEC book with me, but I can almost guarantee that the DDEC ECU will not activate the Jakes under various conditions.  In my case, I learned the hard way that it will not let the Jakes activate if it thinks the clutch is depressed.  It will also not activate the Jakes if the parking brake or high idle are on.  Just makes sense, you don't need/want them on under these conditions. 

All of the functions I mentioned above are interconnected within the ECU software.  For example, you can not put the engine on high idle unless the parking brake is on.

Jim

[buswarrior]

Let's also remember the interaction with the automatic transmission.

In gear, torque converter locked up, typically are the requirements I am aware of.

I've never heard an auto equipped vehicle be able to bark the jakes sitting still, YMMV.

happy coaching!
buswarrior

[Don4107]

Why not just take it for a spin?

[JackConrad]

    On our 8V71 the Jake's are controlled by 3 switches installed in series (all switches must be on for Jake operation). The first switch is the on/off switch to the left of the driver. The next switch is on the Governor and will only be on when the rack is at idle position. The third switch is a pressure switch on the transmission lock-up test port and is only on when the transmission is in lock-up mode. So, in our case, the jakes can only be on when Jake switch at drivers is on, the governor is at idle position, and the bus in rolling, in gear, faster than about 12-15 MPH (speed at which lock-up disengages).  Jack

[Blacksheep]

Don at this time the bus can't be driven. The drive wheels were off and the air bag was installed today but now I see the wheels are back on. Been sitting a while he tells me and its still aired up pretty good so it looks like one major air leak has been fixed.
Jack he tells me what you say is true but not on a ddec engine, just mechanical!
As long as its in the shop, were still looking and searching!
The muffler came today and I brought it down. Hopefully the pipes will be here tomorrow and the exhaust can get finished up!
Ahh gee, what else?

Ace

[RTS/Daytona]

Ace

This may help---> jake Brake / ddec-II trouble shooting guide

http://www.jakebrake.com/service/pdf2/021772.pdf

Pete RTS/Daytona

[Sammy]

Ace, the Jake brake is controlled by DDEC 2 in your Prevost.
You have a Jake switch for low and hi activation.
Your Jake engine brake system is 12 volts.
There is no Jake module.
CB 14 provides 12 volts to Jake switch thru R 56 when DDEC will allow it (providing a ground to term 87 of relay) then switch sends 12 volts to jake solenoids to have Jake action.
DDEC 2 needs to "see" certain conditions  to allow it to provide a ground to R56 for everything to happen.Some of these conditions could be: throttle input, vehicle speed input and possibly more.
Pete (RTSDaytona), if you have any specific input and outputs for DDEC 2 please jump in. I don't have anything here at home for DDEC 2. Thanks.