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Author Topic: Jake question  (Read 1080 times)
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Will & Wife
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« on: December 13, 2008, 03:04:56 PM »

In my owner's manual it states that the Jake can be left on for most driving conditions, especially in commuter and in-town type driving scenarios with lots of stopping and going. However, it strongly advises against shutting down the diesel with the Jake switched on. Any opinions on this and if I do (oops)  Embarrassed shut it down with the Jake left in the 'ON' position, what happens? Can I just flip the switch off before starting next time? Any advice or opinions would be greatly appreciated. Thanks in advance, Will
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NCbob
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« Reply #1 on: December 13, 2008, 03:43:52 PM »

Will, stop and think about this. I get the impression that you don't understand how the Jake's work and it is not my intention to demean you for that. Most of us have to learn and this is the greatest place  for that.

Jake Brakes use a series of electric solenoids to insure that two of the four exhaust valves on each cylinder of half of your engine (4) build compression instead of breathing freely. When you remove your foot from the fuel pedal this drag on the engine is what slows you down slightly when descending a steep grade or you need an assist in city traffic.

The operation of the system is controlled by switches energized by oil pressure.

So to get to your question:  If the Jake electric switch is on at start up as soon as you have oil pressure you will inadvertently be closing four exhaust valves you need to get your engine started and breathing properly at a time when it is cold and needs all the air in can get to warm up to operating temperature.

There is a switch which engages the Jake's when the engine is at idle if left 'On' will defeat your normal start and warm up.

Hope this helps,

NCbob
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Will & Wife
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« Reply #2 on: December 13, 2008, 04:01:06 PM »

NCBob,
I don't find your help demeaning at all. Your answer explained my question in very easy to understand terms. Thank you. I won't forget to flip that switch in the future. Grin It's been a while since, but when I bought the bus most of the dash wiring was screwed up from an RV sales lot's 'mechanic' trying to replace the back-up camera and some other things. It's a 2-stage jake and I think it was permanently in the on mode until I tracked the wires and installed a proper 3-position switch. I drove the bus home in the rain at night without benefit of dash lights etc. But that's another story. Thanks again, Will
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« Reply #3 on: December 13, 2008, 04:25:00 PM »

Will, never a problem.  We drive some pretty complex machines and anytime we can learn how to understand the, like our wives (hehe) we're so much better off.

best,

NCbob
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« Reply #4 on: December 13, 2008, 11:38:54 PM »

Most Jakes will not operate under about 15 psi, and your 8V-92TA probably does not put out much more than 10psi at idle-so the Jakes will just naturally not operate.  No big deal to keep them on all the time-will not hurt a thing.
When I was driving truck, my truck had a 3406B Caterpillar that put out around 40psi at idle.  My on/off solenoid burned out on the engine, so I stopped it by revving it up a bit then hitting the Jake brake, and it would kill the engine.  I did that for 6 weeks without any problems.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
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