I may be buying a Jake from a mechanic that has one on one of his old trucks with an 8v71. He would do the installation for me. He says it will be about a ten hour job not including the electrical. Does that sound right? I was thinking of just having one wire to dash switch to activate it. Since he told me that pressing the accelerator while the Jake is on could be catastrophic, I thought of also having that same switch activate the limiter solenoid that comes on with fast idle. Would something like this be necessary?
If the Jake is installed correctly it should not be possible for it to stay on when the accelerator is pressed. There should be a buffer switch installed that would not allow that to happen. Wiring them to your dash is simple. Have him install and test the Jakes, then do the front stuff yourself, and save some coin.
I was wondering about the ten hours to install...is that right?
Jack
I was wondering about the ten hours to install...is that right?
Jack
Thats going to be about right
Is the buffer switch installed on or around the accelerator pedal or is it on the engine?
Lin, it goes on the engine at the governor housing
Quote from: Lin on February 14, 2008, 10:11:35 AM
Is the buffer switch installed on or around the accelerator pedal or is it on the engine?
The buffer switch is on the governor assembly. You will require three wires from the engine compartment to the drivers area. One wire from the buffer switch to the OFF-HI-LOW switch on the dash and two wires from this switch to the Jakes. These wires go thru the valve cover to the Jake solenoids. You will also require one wire, from a DC source that is hot when the ignition switch is turned on, to the other terminal on the buffer switch.
Richard
10 working hours is right for an experienced mechanic, without wiring to the front.
I ran the wires to the front myself and rebuilt the jake before the mechanic installed them. I would not recommend installing the jakes yourself unless you have experience setting the rack.
Ed Roelle
The deal evaporated. The mechanic had thought that he had a Detroit Jake on one of his old trucks, but when checking them out, it was no longer there. Oh well, it is still something I will be looking into. One question though, he pointed out what I consider to be the fast idle cylinder. It is screwed into the governor housing and has a pin in it that I had thought pushes that idle up when activated. He said that that is where the buffer switch went. Any info on this confusion?
Lin,
The Jake Brake switch replaces the fast idle switch. For about 350-400, Jake will sell you a buffer switch with a fst idle built in. Jack
Hi Lin,
Check out this thread from last summer on my jake install
http://www.busconversions.com/bbs/index.php?topic=5045.msg46610;topicseen#msg46610
Nick-
Thanks for info.
Jack, If the Jake buffer replaces the fast idle, does that mean that you could use the fast idle wiring for the Jake or do other fast idle functions, like the fast idle limiter, still have to work?
I don't have my manual close by, but I think there is only 1 wire from the front to the back to control the fast idle. This wire controls the fast idle solenoid mounted on the bulkhead near the engine stop solenoid. The fast idle control circuit also goes through a couple other switches to insure fast idle only comes on when transmission is in neutral and parking brake is set. Jack
It seems to me that if a person installed a Jake brake without using the buffer switch/fast idle combo, thereby eliminating fast idle, that it would be bad for the engine. I say this becuase the manuals and everything I have read are adamant that any time you must idle for more than 5 minutes, you must use fast idle to avoid wet stacking, fouling the rings and ports and to maintain proper lubrication.
We went with a different way of controlling our Jake Brake. We have an air throttle on our bus. I temporarily installed a pressure gauge on the air throttle actuator and found that it took 5 PSI for the throttle to start opening. I installed a 3 PSI NC pressure switch. This switch opens (disabling the Jake Brake) before the rack opens. We also added a 45 PSI NO pressure switch in the torque converter lockup test port. Lockup pressure is within 15 PSI of main line pressure (175 PSI). The 2 switches are connected in series and control a relay which controls the Jake Brakes. For the Jakes to apply, the throttle must be at idle position and the transmission must be in lockup mode.
NOTE: This is our own design and not approved by Jacobs Brake Co., YMMV, but works for us. Jack