I fired up the old IBM and added pics today.

Had a friend (who owns a '00 Tracker) tell me his front wheel drive had stopped working last fall.  He told me a mechanic had told him his PCM needed replaced and the repair estimate was $800. That was what the CEL code reflected, anyway.  My friend didn't have the $800 for the repair.  I wouldn't have had $800 laying around for this repair either.

Long story short, I went to an area pick-n-pull and pulled an actuator pump off of a wrecked Tracker last Friday. The actuary pump is located (standing in front of the truck) on the left center behind the front bumper.  Literally, it's mounted to the bumper inside.  Took it home and hooked up the wires to a battery charger.  It took right off.  So I started his truck, engaged 4WD and checked his pump.... not running.  So I shut off the truck, unplugged his pump and plugged the new "used" pump into his wiring, started the truck, engaged 4WD and whalla!!:  he now has his 4WD restored... for $25.  I checked the internet and the cheapest I could find a NEW pump was about $173.00 the highest was well over $200.

So I got to wondering about his old pump and why it had stopped working so I took it apart.  

Two bolts (12mm) hold the bracket to the inside of the front bumper. Two rubber hoses are attached to the nozzles on the pump.  One runs to the front diff to pressurize the actuator and the other appears to be a vent that exits on the top left side of the radiator next to the diff breather.  Then there is one electrical connector which has a detent you press with your thumb and they slide apart (sometimes with more than a little effort).  You can remove this pump in less than five minutes without needing jacks or ramps.

Frankly, I don't know why the hell they mounted this thing inside the front bumper right in harms way.  Appears it would be "more" better to mount this pump inside the fender well on the battery side.

The pump:

Three phillips screws (with isolator bushings) hold the pump (which has a plastic housing) to the metal mounting bracket.  

There are three wires running into the pump harness:  red one (power), black (ground), and a pink one (runs from/to the PCM)

Once the pump is separated from the metal housing... there are four phillips screws that hold the electric motor to the pump housing.  Remove them but DON'T attempt to separate the motor yet.

There is a square metal top crimped over the circuit board of the pump.  I took a screw driver and pried the lips up on two sides and it popped the metal cover off. Inside the metal lid the plastic housing has a nice rubber gasket to prevent excessive moisture from entering.

With the cover removed you will see two small phillips screws holding the circuit board in place.  Once these two screws are removed you can pull the circuit board out while pushing/feeding the three wires into the housing (thru a small three hole grommet) in order to to provide the slack for the circuit board to move upwards.  There is a micro switch mounted directly under the circuit board and a black plastic housing clipped over the micro switch which has a plunger in it.  Next to the circuit board is another coil.  This coil and the circuit board are held together by a metal housing with crimped tabs that hold these parts firmly together.

Once the circuit board is out, look inside the housing you will see the end of the electric motor shaft is secured by a "c" clip to a small plastic piston rod that drives the diaphragm to generate air pressure. The motor has a cam secured to the shaft so the piston rod oscillates when the motor runs and drives the diaphragm.  Remove the "c" clip and the motor will then separate from the housing.  

In the case of this actuator pump, the red (power) wire had corroded and broken off the circuit board.  I soldered it back on.  A solder had also broken on the circuit board right over the micro switch.  I soldered it.  I put power to it and the pump sprung to life again.

Assembly is the reverse of the disassembly.  I coated the rubber seals with a light coat of grease and re-crimped the metal cover.  

The point to this thread is that:

a. bad actuary pumps can sometimes be repaired (I found one with a bad diaphragm and I couldn't repair it)  
b. although these SOTF diffs set ups are a pain in the butt, there are really just three areas which normally fail that causes us to lose our front wheel drive:  The actuator pump, a vacuum leak in a hose, or the actuary in the front diff leaks and won't hold pressure.  

For $20-$30 bucks you can go to your local pick-n-pull, grab one, test it for function, then keep it in your spare parts when you're wheeling so IF you need it when you are out on the trail or snowy road, you got it.  The only wreck I came across that didn't still have the actuary pump on it was wrecks that were missing the entire front bumper.  I actually pulled one from a front end wreck that had severely bent the housing holding the actuary pump... but the pump still worked.  These pumps are also inter-changeable within many years of 2nd gen Trackers/GVs.  So you don't have to find your EXACT model year in the yard to find a pump that will work for you.

And finally, there are a few people who will say a used pump will fail eventually.  I totally agree, but I can also swap out eight or nine used pumps before I would have the $170 plus dollars invested for the cost of a new pump (and a new pump can fail as well).  I'm good with that.  

That's a great write-up.  Maybe it should be a sticky, or in a how-to section, so it doesn't get lost in the general pool.

Thank you much, IanL.  What makes this idea is even more financially attractive is I bought THREE actuary pumps for $38 total.  Of the three pumps I bought, one had the defective diaphragm (that I mentioned above) but the other two worked like champs.  So I averaged my estimate (above) for the cost of a pump.  It is quite doable to mate a good motor from one pump to another pump with a defective motor and gain one working unit from two.  No doubt prices (and the deals) vary depending where you are located, but the repair or replace with a used pump remains a cost effective option for an inexpensive repair.

We need more of these "how to"s on the board...most definatly at some point someone will ask about it .......
by the way I did the samething but for the egr valve....bought it from a junkyard for 40$cdn  new egr valves are expensive (specially in a recession) did the work myself thanks to a haynes repair manual and this board.........

Always keep old parts that you can POSSIBLY rebuild and use again......kept my egr valve.......3 years later......50-60ks egr valve went again just replaced with original (rebuilt and cleaned) and i still have a spare

my chevy tracker is gonna hit 200 000km soon and its been all across canada without a single MAJOR problem

I agree and confer with SnOvv regarding the issue of more "how to's" and "DIY" stuff. I also have similar issues regarding the front actuator pump. Upon engaging to 4WD, the indicator light blinks every so often and based on the forum write-ups, the blinking is due to an air leak.

How does one contain/prevent this air leak? For convenience of maintenance/damage due to off-roading, have you tried relocating the actuator pump inside the engine compartment? Suzuki may have a reason for mounting it behind the bumper stiffener (away from engine heat,maybe). The only problem I see is how to lengthen the red, black and pink wirings and prevent loose contact in the process (soldering and using shrink wraps maybe in order), lengthening of the 2 hoses and fabricating a heat shield (made from aluminum or hard plastic) to protect the pump from the engine heat.

I would like your views on this particular project.

You may well be right.  Heat may have been the driving factor on placement of the pump and unless you are fording a stream 3 feet deep it is in a fairly dry area as well.  From looking at the pump they appear to be sealed up failrly well but if I were to ever break down and actually buy a new pump I would place some additional sealer around the 3 wire grommet where the wires pass into the circuit board enclosure and also where the two wires go into the motor case and even some dabs on the wire junctions which are shrink wrapped.  There was corrosion iniside the shrink wrap on the one I disassembled as well.  But again, this was a ten year old truck.  Beyond those areas, the wire couplers (on the ones I picked up) were all in good shape with little to no corrosion at all.

As far as the wiring harness for the pump, it is held to the frame body a few inches from the pump with a clip which can be removed (on the trucks I tinkered with).  The additional slack should allow the pump to be repositioned somewhere inside the lower passenger front wheel well.

The other factor that probably comes into play may be simply this little pump only knocks out between 5-8 pounds of pressure.  The pump would probably lose some of this "incredible" pressure puffing air through longer spands of tubing.

Beyond the above speculation, I do not know.

Thank you for the additional inputs Nprecon regarding the relocation of the actuator pump. From your experience, what could have been the source of the air leak causing the 4WD indicator light to keep on blinking?

Hey, thank you for showing me that, both my Zuks are 9 and 10 years old and I have been thinking about those pumps, I am really glad you showed this, thank you for posting the pics and taking the time!!!  Dave

You guys are very much welcome.  Eyb, I am far from a master mechanic and I certainly don't have an ounce of the experience many of the guys here on the net who are, but my GUESS as to why you have/had a blinking 4WD light when engaged is probably one of the following:

1.  you have a kink OR leak in an air hose to/from the actuator pump and the actuator in your front diff
    1.a. a slight twist to number 1 above is it is conceivable that some foam from the front diff may have backed up into the
          air line and constricted the hose/metal lines from the actuator.  I mention this possibility because a few of the
          pumps I removed DID have some oil foam build up in the lines in them and I pondered how much restriction in the
          airline from this foam it would take to denegrate the already anemic pressure generated from these pumps. You
          could blow out the lines to check BUT never use high pressure air in the lines when they are connected to
          EITHER the front diff or the pump. You will blow diaphragms for sure that may have been alright.  
          Remember these diaphragms sip air pressure at only 5-8PSI max. 90-100PSI air pressure will toast them.

2.  your actuator pump might be weak and not kicking out the 5.4-8.25 psi the actuator in the diff requires to engage
          the 4WD. Bear in mind JUST because the pump "makes noise" and puffs air does NOT mean it is generating the
          required PSI. If the diaphragm in the pump has a hole in it the pressure will be sub standard (maybe 3
          -4PSI?) and eventually be zero pressure as it completely fails/ruptures.  You have to actually check the air pressure
          output with an accurate pressure guage.
     2.a. conceivably, if your diff oil has not been changed reguarly (or at all) a heavy varnish coating inside the gear
          housing could have developed causing additional drag denegrating the actuator air pressure effectiveness, not highly
          likely as few times as the front axle is used as compared to the rear diff.
 
3.  the actual actuator within your diff has a slight leak/not holding the air pressure, and so is jumping into and out of 4WD

(My apologies for the lines being jacked up on this post.)

One last thought on this actuator pump, a method of checking your pump (mentioned by Yankee Tim and others before) is to:

- lift and support your vehicle off the ground (clear the tires)
- with the actuator pump off (2WD), turn one wheel, the other wheel should remain stationary as the other is turned
- with the pump on (4WD), turn one wheel, the other front wheel should turn in the opposite direction
- you should have 10-14 volts running through the actuator pump
- you should have 5.40-8.25 psi from the pump (as measured with an actuator pressure guage)

Also, I used a male end cut from a wrecked vehicle to test the pumps by hooking up a battery charger to the male lead.  Makes it a bit quicker to connect and disconnect to the various pumps quckly.

Thanks again nprecom for the invaluable inputs. I will keep it for reference

   1.a. a slight twist to number 1 above is it is conceivable that some foam from the front diff may have backed up into the
          air line and constricted the hose/metal lines from the actuator.  I mention this possibility because a few of the
          pumps I removed DID have some oil foam build up in the lines in them and I pondered how much restriction in the
          airline from this foam it would take to denegrate the already anemic pressure generated from these pumps. You
          could blow out the lines to check BUT never use high pressure air in the lines when they are connected to
          EITHER the front diff or the pump. You will blow diaphragms for sure that may have been alright.  
          Remember these diaphragms sip air pressure at only 5-8PSI max. 90-100PSI air pressure will toast them.

I could be wrong - but for oil foam to get into the lines, I think that would indicate a failed (ruptured) actuator.

That would make sense.

Holy crap, is that what that thing is?  Lol, I thought it was an airbag sensor or something...