Isoton pick up tubing (6605236, I am getting these part numbers from the B/C
web site) may be blocked (perhaps not all the diluent was washed out of the
lines before storage and there is a salt blockage in a tube fitting) or
pinched.  On larger instruments, a common problem is that there is a hole
(or a tubing is off the a fitting) in the tubing somewhere around the
primary diluent pump.  Does this intrument have "pinch valves"?  If so that
is an important point to role out.  Assuming that the primary diluent ( i.e.
isoton) pumps are like those in larger instruments and are made of clear
plastic,...can you see the the pumps move up and down?  Can you remove
tubing from somewhere above the pumps, attach a tubing to a large syringe to
see if you can pull isoton through from the reagent pack or source of
diluent?  You could also try poping off a line and filling the pumps or
chambers from a large syringe...just to try to get  the instrument past the
"self check" point.  This last has a low probability of doing anything, but
if you have got this far, what the hell.
Although I have never heard of this instrument, I did a search at Beckman /
Coulter and found one can still get a service manual (4237161).
http://www.beckmancoulter.com/customersupport/partnumbers/default.asp

I also note that B/C has an unline troubleshooting page
(http://www.beckmancoulter.com/customersupport/troubleshooting/default.asp)
.  Even if you don't have a contract, or that this instrument is no longer
supported, it might be worth a try to get some free advance from them.

Well.  What happen?