Fast Idle switch Engine Brake

[Nicholas Soldevere]

Ok guys , I have another one for the Beaver Wizards here, all your help is much appreciated btw. 

My "Fast Idle" switch on the side panel does nothing. In probing it, I can only see 3.6vdc, in my mind it should be 12vdc. Is it supposed to be 3.6?   I can find no wire print related to this system. Does anyone have a wire print to it. BTW, I can go to fast idle using cruise control switch which I suppose is an alternate method.

As an aside, I was working on Engine Brake system yesterday. It has been a very INTERMITTANT system since I owned the rig. As we all know that's not good. I found where the previous owner had wired the eng brake to receive power from the brake light relay using a nice wire salvaged from an old computer power wire. Anyways, after removing the po's mess, and on test drive I found the engine now activates when removing my foot from the accelerator. I suspect this is the reason they wired it like that.

I know there are 2 stages to this engine brake, can anyone explain the differences from the switch forward position and the switch back position?

[David T. Richelderfer]

Please put your coach's year and model, and your engine in your display info.  That would allow owners with similar equipment to help.

Is your engine brake a PAC Brake or a Jake Brake?  If it's a PAC Brake, then it may need servicing - like greasing, I think is what they do.  It runs in the exhaust stream, so it requires regular maintenance.

Our coach has a two-position Jake Brake.  The rocker toggle for it has three positions; the down position to the rear is the little Jake, the center position is Jake off, and the down position to the front is the big Jake.  I believe the little Jake position uses three cylinders versus the big Jake uses six cylinders.

Our coach does not have an engine-idle-increase switch to my knowledge.  I use the cruise control and accel buttons.

[Fred Brooks]

    Nick,
 We cannot help you without some information about your coach! Please update your profile so we can assist you. CAUTION: probing the fast idle switch! that wire could go to the ECM (electronic control module). It is a computor that controls all engine decisions. 3.6 volts is computer voltage! If you start probing and decide to send 12volts down the wires to experiment it WILL damage the ECM. Please Advise and thanks for your inquiry. We are here to help you, Blessings Fred

[Nicholas Soldevere]

Signature added, sorry folks, I guess I thought everyone knew what I have. My fault.

Im wondering how I would be able to know the difference between a PAC Brake and Jacobs?

[Nicholas Soldevere]

    Nick,
 We cannot help you without some information about your coach! Please update your profile so we can assist you. CAUTION: probing the fast idle switch! that wire could go to the ECM (electronic control module). It is a computor that controls all engine decisions. 3.6 volts is computer voltage! If you start probing and decide to send 12volts down the wires to experiment it WILL damage the ECM. Please Advise and thanks for your inquiry. We are here to help you, Blessings Fred

I dont know why, but I was thinking ECM volts is usually 5v, but if its 3.6 and the signal is there then, something down line.
I would love to find a wire diagram on it.

[Fred Brooks]

   Nick,
  To answer your question, A pac brake closes off your exhaust from escaping at the manifold output thus creating a back-pressure in the engine to slow you down. It also causes the transmission to down shift to assist in slowing the coach down. A Jake brake works differently, It turns the engine into a Compressor momentarily to slow you down. If you push the switch forward it is max engine braking and it automatically shifts the engine from 6th to 4th gear to assist in braking. Pushing the switch towards the rear is less engine braking. Caution: Driving at 70 mph and engaging the Jake brake may OVER REV the engine and cause damage. Do you have a Smart Steering wheel?. If so, it may be the issue if you have one. The cruise control and fast Idle are controlled by it. Incidentally, if your cruise control and your jake brake are both engaged at the same time there is a conflict. It is common issue for the contact plate under the steering wheel to get dirty from the carbon brushes contacting it for 23 years. It sends misinformation to the VIP control module that executes the commands you are asking for. I just re-read your original post, if your fast- idle switch is on the side consol, then you do not have a smart wheel by VIP. Hope this helps, Fred

[David T. Richelderfer]

I must comment on the auto-downshift when the engine brake is actuated.  If you like that feature, then okay.  But I did not like it and had our coach's transmission reprogrammed to remove the auto-downshift feature.  The first day I drove the coach from Eugene, OR over the hill to Sisters, OR, that auto-downshift feature scared me to death!  I thought the engine would go flying out the backend!

It wasn't long before I had it reprogrammed to NOT auto-downshift.  This was done at the Kenworth truck shop in Pasco, WA. 

[Fred Brooks]

    I agree with David, I had mine reprogrammed to go to 5th instead of 4th and then manually choose the gear I want to stay in going down a 7% grade at the speed I feel comfortable with. Fred

[Nicholas Soldevere]

   Nick,
  To answer your question, A pac brake closes off your exhaust from escaping at the manifold output thus creating a back-pressure in the engine to slow you down. It also causes the transmission to down shift to assist in slowing the coach down. A Jake brake works differently, It turns the engine into a Compressor momentarily to slow you down. If you push the switch forward it is max engine braking and it automatically shifts the engine from 6th to 4th gear to assist in braking. Pushing the switch towards the rear is less engine braking. Caution: Driving at 70 mph and engaging the Jake brake may OVER REV the engine and cause damage. Do you have a Smart Steering wheel?. If so, it may be the issue if you have one. The cruise control and fast Idle are controlled by it. Incidentally, if your cruise control and your jake brake are both engaged at the same time there is a conflict. It is common issue for the contact plate under the steering wheel to get dirty from the carbon brushes contacting it for 23 years. It sends misinformation to the VIP control module that executes the commands you are asking for. I just re-read your original post, if your fast- idle switch is on the side console, then you do not have a smart wheel by VIP. Hope this helps, Fred

Thanks Fred, I do believe I have a smart wheel, it has buttons for lights and cruise, I don't know why there is also a Fast Idle switch as well on the side panel.  I have found on the one test drive I did yesterday which wasn't out on the highway as I was just checking the eng brake. The cruise didn't engage with eng brake switch on. Now, I'm thinking and have known for awhile that I need to get into that wheel and clean those contacts on the clock spring as the cruise control functions from the wheel aren't all there, all I have is On/Off and Resume, so I cannot change the speed, 68.5 mph is where is stuck at, which also seems to be the sweet spot for the rig anyway, so. The cruise is problematic, another issue I discovered last trip out is , it doesn't automatically disengage when stepping on the brake.

[Nicholas Soldevere]

I must comment on the auto-downshift when the engine brake is actuated.  If you like that feature, then okay.  But I did not like it and had our coach's transmission reprogrammed to remove the auto-downshift feature.  The first day I drove the coach from Eugene, OR over the hill to Sisters, OR, that auto-downshift feature scared me to death!  I thought the engine would go flying out the backend!

It wasn't long before I had it reprogrammed to NOT auto-downshift.  This was done at the Kenworth truck shop in Pasco, WA.

Good advice and info, thankyou! I'll be getting out on the road with it in a couple weeks and will see this feature 1rst hand and decide if I like it our not. I'll run with your advice and get it programed out if I don't. Since the Eng brake has been "rigged" since I owned it and has been intermittent I have never really experienced the oem design features, so, I'm excited to get it out and run it.

[Joel Ashley]

A so-called “Jake brake” is commonly, as others here have described, built into the engine itself on the larger on-highway engines.  It’s often referred to as an “engine brake” or “compression brake”.  Yours, Nicholas, being a 400 implies to me that you have the “exhaust brake” type known commonly as a “Pacbrake” externally mounted to the exhaust manifold of smaller engines.  If like on my CAT 400, that unit, though generically a “PAC”, is actually made by Jacobs Vehicle Systems, not necessarily by the original manufacturing company (* see link) making for some confusion.  I believe Jacob’s Vehicle Systems was bought not long ago by Cummins.  It’s best to discern external exhaust brake, like Pacbrake by either that mfr or JVS, from internal engine compression brake, like Jake brake.

The butterfly type valve that comprises a Pacbrake can corrode with non-use and freeze up, so the mechanism won’t close it upon switch activation.  Owners often are unaware that regular lubrication is necessary to prevent that.  A lubricant designed for that application is available at many outlets;  follow directions and check for online videos for proper use:

https://pacbrake.com/superlube-exhaust-brake-lubricant.html?srsltid=AfmBOoqUSxfm7GhjIW8FzRVxXg6G_fVir9eJiqn_bGMV8s6gd_XpBOIk

* https://79cd0798.flowpaper.com/brakescatalogueweb/#page=1

Joel

[Nicholas Soldevere]

A so-called “Jake brake” is commonly, as others here have described, built into the engine itself on the larger on-highway engines.  It’s often referred to as an “engine brake” or “compression brake”.  Yours, Nicholas, being a 400 implies to me that you have the “exhaust brake” type known commonly as a “Pacbrake” externally mounted to the exhaust manifold of smaller engines.  If like on my CAT 400, that unit, though generically a “PAC”, is actually made by Jacobs Vehicle Systems, not necessarily by the original manufacturing company (* see link) making for some confusion.  I believe Jacob’s Vehicle Systems was bought not long ago by Cummins.  It’s best to discern external exhaust brake, like Pacbrake by either that mfr or JVS, from internal engine compression brake, like Jake brake.

The butterfly type valve that comprises a Pacbrake can corrode with non-use and freeze up, so the mechanism won’t close it upon switch activation.  Owners often are unaware that regular lubrication is necessary to prevent that.  A lubricant designed for that application is available at many outlets;  follow directions and check for online videos for proper use:

https://pacbrake.com/superlube-exhaust-brake-lubricant.html?srsltid=AfmBOoqUSxfm7GhjIW8FzRVxXg6G_fVir9eJiqn_bGMV8s6gd_XpBOIk

* https://79cd0798.flowpaper.com/brakescatalogueweb/#page=1

Joel

Thankyou Joel, so if I peer down into the engine bay from the bedroom access hatch, I should find the Pacbrake mounted to the exhaust manifold, or would it be better access from underneath?

Ok, I did some research after asking the question and found this video for the ISL

Heres a link to a video, shows it on top.
https://www.youtube.com/watch?v=EJIZ7AjqU8s

[Joel Ashley]

I can’t be absolutely certain since you have a different engine than ours;  but with the bedroom/wardrobe floor hatches open and me facing the rear of the coach, the Jacob’s brand exhaust brake is in the manifold, to my right on top of our CAT C9 engine.  It’s relatively easy to access.  There are several points that one should use the lube bottle on:

https://pacbrake.com/mm5/pdfs/L6111.pdf

There’s also a video on YouTube -      https://www.youtube.com/watch?v=E_wX98sHBpU

Admittedly, having been sidelined long and with poor memory I’m only postulating here, but you can have, engine running, a helper activate the dash switch while through the hatch you observe the unit’s action to see if it’s working as it should (watch where you put your fingers).  An engine speed beyond idle may be necessary.  There should be a solenoid nearby that routes air to the unit;  to test air and mechanicals you may be able to apply an external 12v to it as an alternative to a helper in the drivers seat.  I’m not sure what your reference to a two stage brake is regarding, as our switch is simply either on or off.  Others here with more recent experience may provide enlightenment.

As for your complaint of “intermittent“ operation, keep in mind that cruise control disengages if the exhaust brake activates, like it does if you depress the brake pedal.  The exhaust brake quits if the fuel pedal is depressed or if engine speed is too low.  A complete checkup would see that both the electrical and air sides of the pacbrake system are functional, as well as the mechanical lubrication side.

Joel

[Nicholas Soldevere]

I can’t be absolutely certain since you have a different engine than ours;  but with the bedroom/wardrobe floor hatches open and me facing the rear of the coach, the Jacob’s brand exhaust brake is in the manifold, to my right on top of our CAT C9 engine.  It’s relatively easy to access.  There are several points that one should use the lube bottle on:

https://pacbrake.com/mm5/pdfs/L6111.pdf

There’s also a video on YouTube -      https://www.youtube.com/watch?v=E_wX98sHBpU

Admittedly, having been sidelined long and with poor memory I’m only postulating here, but you can have, engine running, a helper activate the dash switch while through the hatch you observe the unit’s action to see if it’s working as it should (watch where you put your fingers).  An engine speed beyond idle may be necessary.  There should be a solenoid nearby that routes air to the unit;  to test air and mechanicals you may be able to apply an external 12v to it as an alternative to a helper in the drivers seat.  I’m not sure what your reference to a two stage brake is regarding, as our switch is simply either on or off.  Others here with more recent experience may provide enlightenment.

As for your complaint of “intermittent“ operation, keep in mind that cruise control disengages if the exhaust brake activates, like it does if you depress the brake pedal.  The exhaust brake quits if the fuel pedal is depressed or if engine speed is too low.  A complete checkup would see that both the electrical and air sides of the pacbrake system are functional, as well as the mechanical lubrication side.

Joel

Hi Joel and thanks, I'm right there with you on the memory thing. The rigors of an older brain apparently. Mine has the Cummins ISL 400. My switch on the side console is a 3 position switch, center- off, fwd and back. As far as intermittency goes, the po had it wired to the brake light relay in the fwd electrical bay with a computer power cord with the ends cut off. It kind of worked sometimes. I just find it amazing the work around folks will go through to disable a perfectly good system, and do it with parts taken from a garbage can.

Im making a plan to follow yours and others advice and get in there to lube it and put it on a regular maintence schedule if I can remember.