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Air Tank Acquisition and Installation.  My next task was to acquire and install an air tank.  This is another area where I could have saved money, but chose not to.  I realize that I could have used a variety of tanks (e.g., truck air-brake tank, welding gas tank, air compressor tank, etc.), but I just didn't feel like trying to find one of the correct size, especially since Sun Performance Products already had exactly what I wanted at a fairly reasonably price.  So I purchased their 2.5-gallon air tank, which measures 6 inches by 24 inches and is rated at 150 PSI, for $72.99 (plus s&h).  It includes mounting brackets and five ¼-inch NPT openings.  

I considered two mounting locations for the air tank: underneath the Jeep, on the driver's side, next to the rear drive shaft, opposite the muffler.  And in the engine compartment, right in front of the firewall.  After crawling under the Jeep and seeing several dents and scratches in my muffler, I quickly decided that I really didn't want the tank down there.  Besides the better protection it would afford by locating the tank in the engine compartment, it would be much easier to install, I wouldn't need as much plumbing, and I'd be able to make better use of all those NPT openings.  

The tank already had two mounting brackets on one "side", with welded-on nuts.  Using a few pieces of 3/16" steel strap and 2" channel, I created a mounting bracket which bolts to the firewall.  The tank, of course, bolts to the 4 holes showing in the "U" channel.  It fits pretty tight under the hood, but there's lots of clearance above the top of the engine.  I have no problem getting to the engine oil fill cap or the dipstick (as you can perhaps see in the picture in the paragraph above).  Changing the spark plugs, on the other hand, is another story.  It's much easier to unbolt the tank and lift it up some to get the the last two plugs.

Plumbing (Fittings, Hoses, Regulator, Gauges, etc.).  The last major step in the process was to purchase and connect all the plumbing parts.  I tried to draw the entire system on paper, piece by piece, to make sure that I knew what all pieces I would need (It didn't work--I still ended up making about three trips to the parts store).  

The picture on the left is a good shot of the compressor-to-air tank set-up.  The tiny little cone shaped piece on the end of the suction manifold is actually a filter.   On the discharge side, a ½-inch stainless steel braided air hose connects the discharge manifold to four key components on the compressor-to-tank set-up.  The first "filter" is an oil separator; the second is a moisture separator.  The large rectangular part attached to the air hose is a check valve (or one-way valve).  It allows the air to flow freely into the tank, but not back to the compressor.  After the check valve, hanging from the "T" fitting, tucked down between the battery and the engine oil dipstick, is an adjustable pressure switch.  I have it set to turn on the compressor when the pressure in the system drops below approximately 90 PSI, and turn off the compressor when the pressure reaches 120 PSI.  

 The pressure switch is controlled by a master switch, which is mounted inside the Jeep, on my Tuffy center console, immediately behind the gear shift lever.  The master switch is powered by an "ignition-switched" circuit, so the compressor can't receive power with the key in the off position.  The master switch activates a heavy-duty 12-volt relay (which happened to fit very nicely inside the pressure switch housing under the hood), connected directly to the battery via a 20-amp in-line fuse.   With this set-up, the electrical load of the compressor is borne by the battery, and not the Jeep's electrical circuitry.  (Note: a few months after I completed this project, I installed  Painless Wiring Weatherproof Circuit Isolator.  As a result, I decided to remove the relay.  The compressor is now powered by a dedicated 20-amp circuit, still via the master switch).  Back inside the cab, opposite the master switch, I installed a small green light and wired it to the master switch (which illuminates whenever the ignition key and the master switch are both in the "on" position).  Finally, between the switch and the light, I installed a 1½-inch 0-160 PSI pressure gauge so that I could monitor the system's status from inside the Jeep.  This gauge is connected, via high-pressure tubing, to the "cross" fitting on the front of the tank that also houses the under-hood pressure gauge and the safety valve.

The picture to the right is the "business" end of the tank, which contains four ¼-inch NPT openings.  The opening that faces the firewall is sealed off with a plug (there wasn't enough room back there to attach anything anyway).  The opening on the bottom of the tank contains a drain cock (not visible in this photo), which I will periodically open to drain any moisture that may have accumulated in the tank. Within the left opening (facing the front of the Jeep) is a 4-way ¼-inch female fitting.  The three openings in the fitting (the fourth is used to secure it to the tank) contain a fitting and tubing that "powers" the in-cab pressure gauge, a 50-200 PSI adjustable pop safety valve (also not visible in this photo),  and a 2-inch 0-160 PSI pressure gauge on the top.  As you can see from the gauge, the tank is full.  Since the tank is rated at 150 PSI, I have the safety valve set to "pop" at approximately 140 PSI.  I set and checked the operation of the safety valve by overriding the pressure switch and letting the compressor run until the safety valve "popped" and released the excess pressure.  The opening on the end of the tank contains my pressure regulator (the thing with the black knob on top and the 1½-inch gauge on the front) and a female quick connect (for connecting my air hose), which attach to the tank with an elbow and a 2½-inch nipple.  Plugged into the quick connect is a capped male nipple, for the sole purpose of keeping dirt out of the quick connect.  On the other end of the "T" fitting that houses this quick connect is an air hose that runs underneath the Jeep, all the way to the back, and attaches to another quick connect, which I installed directly under the passenger side tail light for convenience.

And that's about it!  Here's a picture of the finished product.  I think it turned out to be a very "clean", professional looking installation.  So far, everything seems to work perfectly and I have not been able to detect any leaks in the system.  And here's a cool story about how I first used my new system.  About two days after I finished it, my son (Stephen) and I were coming out of Wal-Mart and, upon arriving to the Jeep, we saw a lady pumping some Fix-A-Flat into one of her tires.  After expelling the entire contents of the can, her tire was still dangerously low on air.  So, of course, I jumped in and said, "Ma'am, I can pump up that tire for you in a jiffy!"  Okay, I didn't really say the jiffy part, but you know what I mean.  Boy, was she surprised when I pulled the air hose from underneath my hood and proceeded to air up her tire in about 10 seconds!   I must have been her hero that day!  Made me feel real good, too!!  :-)

Click here to view schematic diagram of entire system