Jacobs engine brake/ high idle

[George Lowry]

HI Ernie,

Not sure which engine you have. If it is the Cat, I don't know
diddley, but if it is a Detroit.... IF they used the standard Jacobs
unit, it does three functions. The primary function is as a buffer
screw which is designed to take the loping out of the engine at idle.
Adjustment is critical. Book says to turn it in until there is an
increase in rpm not to exceed 15 rpm. best done with an electronic
digital tach.
Second function is to activate the micro switch that activates the
Jake brake. Purpose of this micro switch is to assure that the engine
is in the idle position before activating the Jake. Again a critical
setting. Last function is the high idle where a pneumatic cylinder
pushes a rod inward to increase the governor setting giving you the
high idle. All three of these functions are performed by the same
push rod and, if not set correctly, one or more will not work. If you
don't have the Jacobs manual for the Jake Brake, best get a copy of
one for the proper method of setting it. I gave mine away with the
coach so can't help other than memory, and you know how b ad that can get.

Another way is to jumper the micro switch which will allow the Jake to
operate without that protection. To be safe, you will have to turn it
on and off manually from the driver's station. Not only an
inconvenience, but it can be forgotten. You could do that as a test to
see if the problem is at the micro switch.

Hope this is of some help.

George Lowry
'06 Alpine Apex - Formerly '95 WBDA 4203
Spearfish, SD traveling to SOCAL.



Ernest Ekberg wrote:
> I have an inoperative engine brake and high idle. Steve Gureasko and I
> took the push rod assembly apart and removed the 2 o-rings and
> reassembled it and put it back on the coach. No high idle.Has anyone
> troubleshot this system? Before I head back to Montana, the Jake brake
> is a must have. Thanks, Ernie Ekberg, 83pt40 in louisiana
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