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On
Board Air
by Dan Dohrn
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n2jeepn.com's official
project Jeep 
gets On Board Air
Airing down your tires is often a requirement of many off-road adventures. Airing down is the easy part, it’s getting the air back in that becomes the challenge. There are a few options out there, such as 12v compressors, a Power Tank, or a York air conditioning compressor run by your engine. A Power Tank holds a limited amount of air and takes up a large amount of space. A 12v compressor is small, but does simply does not live up to the task of providing enough air. That leaves the York. If set up with an auxiliary air tank, the York will provide a very impressive amount of air. Enough to air up your tires in a matter of minutes and run air tools.
After locating the proper
York Compressor to use for my system, I removed the
pulley and decided to clean up the compressor and give it a coat of black paint. The cleaning turned out to be a lot of work since there was a thick layer of greasy dirt and lots of little crevasses for it to get down into. The paint didn’t turn out perfect, but since the York is aluminum, there is no chance of rust, so I didn’t worry about it much.
The next step was to decide how I was going to mount the compressor to my engine. I was originally going to go with one of Brad Kilby’s kits from
www.onboardair.com. They appear to be very nicely
 made kits, but I wanted to save some money
and have the enjoyment of putting together the whole OBA system myself. So off to the junkyard I go. I spent a couple hours wandering around only to find a gazillion mounting brackets for V-8’s. I finally found an Eagle station wagon
with a 258 that had some of the brackets and idler pulleys, but not the bracket to mount the York compressor. I figured I was going to have to have a bracket made or spend a lot from a specialty Jeep shop. Finally, I tried a tiny local junkyard that only has Jeep parts(I had tried there before, but they were closed). Sitting in a cardboard
box were all the brackets I needed. You
need the brackets in the drawing to the left and an additional
bracket to relocate the alternator as seen in the picture to
the right.
The brackets all mounted to the engine without any trouble. The alternator
bracket did take a little time to figure out exactly how it went on. Below are pictures of what the brackets look like mounted to
the 258 engine:
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| New alternator mount |
York bracket |
Idler pulley &
bracket |
The next step after mounting the brackets and
idler pulley is to mount the York compressor. This was
slightly challenging due to the limited amount of space
between the York mounting bracket and the alternator. You will
need to move the alternator out of the way in order to have
access to a couple of the York mounting holes. The next thing
to do is measure for the v-belts. I first adjusted the idler
pulley bracket and the alternator (the two moveable items to
adjust the belts tension) to slightly less than half way to
give plenty of room for belt adjustment. I then grabbed a
section of rope and wrapped it around the path of the pulleys
and measured the rope for belt length. You may need to add an
inch or two onto your rope measurements since the rope will
sit farther down in the V-belt pulleys than the belt
will. The belts I ended up with were a 17300 (30 inches)
for the York to alternator belt, and a 17560 (56 inches) for
the belt that went from the York to the idler pulley and then
down to the main crankshaft pulley. The belt to the power
steering pump and fan can be used same as the stock
setup. Below are pictures of the mounted York and a
diagram of the V-belt setup for my 258 after the York
install.
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York mounted to 258 |
Pulley diagram |
Another view of York |
After the York is mounted to the
engine, then you need to plan out and hookup the air lines. I chose to
mount my 2.5 gallon tank from www.onboardair.com
in front of the gas tank under the tub of my Jeep. There is plenty of room for
it there and it is out of the way and protected from most things hitting it. For
the manifold, I used a 1/4 NPT female pipe cross. I minimized what was
under my hood by putting the relief valve and both the front and rear air lines on
the tank. That left me with only a pressure gauge, the pressure switch (Square D
part# 9013FHG12J52M1) and an
oil/water filter under the hood. For the fittings on the York, I decided to
purchase the Rotolock fittings from onboardair.com. I used a PCV breather filter
from an import car for my intake filter. It looks like a mini K&N
filter.
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| Rotolock fittings |
Under hood plumbing |
OBA manifold |
2.5 gallon tank |
I ran the air lines along the frame rail to keep
them protected from getting snagged on anything or getting any damage from
excessive rubbing. I put a quick disconnect on the front under the
driver side fender. For the rear quick disconnect fitting, I got a little more
creative. Since H8PVMNT has a YJ tub, there is an unused hole on the driver's
side rear of the tub where the fuel filler for the YJ was originally located. I
used that hole for mounting my rear quick disconnect and it is protected by the
flip down license plate. To protect the front quick connect from accumulating
dirt and mud, I bought some 7/8" furniture feet that you would use on
a card table or chairs. They are a snug fit and will keep the connections free
of dirt, and best of all they are cheap.
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| Air line routing |
Front quick connect |
Rear quick connect |
Rear hidden by plate |
Here is a "schematic" of
the parts I used for the airline plumbing. It is not to scale, just a
representation of the parts I needed for my system. Click for a larger view:
The electrical connections are really quite
simple for this. I mounted a lighted switch under my dash and
ran one wire to an ignition switched source on the fuse box,
one to ground, and the third to the pressure switch. Then you
simply wire the pressure switch tot he clutch wire of the York
and you are set. The switch is wired to a 12 volt source on the fuse box that is
only hot when the key is on, that way the York clutch will not
get power while the engine is not running and drain your
battery. The pressure switch is pre-set to come on at 95psi
and turn off at 125psi. When the engine is running and the
dash switch is in the on position, the compressor will
automatically turn on and off based on the pressure in the
tank. With the switch in the off position, the compressor
pulley freely spins and does not pump any air, regardless of
the pressure in the system.
I haven't added up the expense of the OBA
system yet, but as with all projects it turned out to be more
than expected due to a gazillion trips to the hardware store
for little bits and pieces I forgot to buy. It was a very
rewarding project however and it will see much use in the
future.
If you need help identifying the correct York
compressor, go here: Selecting the Correct
York
If you have any questions, email me: n2jeepn@cableone.net
n2jeepn.com
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