nozzle, used with the DB2 fuel injection pump, is opened outward by high fuel pressure and
closed by spring tension (fig. 5-22).
It has a unique feature in that it is screwed directly into the cylinder head An outward
opening valve creates a narrow spray that is evenly distributed into the precombustion
chamber. Both engine compression and combustion pressure forces assist the nozzle spring
in closing an outward opening valve. These factors allow the opening pressure settings of
the nozzle to be lower than those of conventional injectors.
injection, a degree of swirl is imparted to the fuel before it actually emerges around the
head of the nozzle. This forms a closely controlled annular orifice with the nozzle valve
seat, which produces a high-velocity atomized fuel spray, forming a narrow cone suitable
for efficient burning of the fuel in the precombustion chamber.
The nozzle has
been designed as basically a throwaway item. After a period of service, the functional
performance may not meet test specifications. Nozzle testing is comprised of the following
Each test is
done independently of the others (for example, when checking the opening pressure, do not
check for leakage). If all the tests are satisfied, the nozzle can be reused. If any one
of the tests is not satisfied, replace the nozzle. For testing procedures, consult the
manufacturers service manual.
When testing nozzles, do not place your
hand or arms near the top of the nozzle. The high-pressure atomized fuel spray from the
nozzle has sufficient penetrating power to puncture flesh and destroy tissue and may
result in blood poisoning. The nozzle tip should always be enclosed in a receptacle,
preferably transparent, to contain the spray.