TRUCK SERVICE MANUAL
3. Drain sediment from air inlet trap daily or weekly
6. Maintain air cylinder oiler at 1/2 to 1/3 full of
as required depending upon amount of
injector test oil at all times to insure proper
A yellow indicator will appear in upper bulb when
7. All fittings, filter oiler and bubble-checker bowls
sintered filter becomes clogged with foreign
(upper and lower) must be kept tight and free
matter. The filter must then be removed and
from air leaks.
cleaned with solvent.
8. Any oil that collects in bowl of separator mounted
4. Do not obstruct flow meter vent in any way. Oil
by dry type filter must be drained regularly. This
and oil mist must never be allowed to enter
separator also contains a sintered filter which
either the drain of inlet of flow meter as this will
must be cleaned in solvent at least twice yearly
cause float to stick to the sides of tube.
according to all available data.
5. Do not readjust or move injector plate supports
9. All available data indicates that dry type filter
element should be changed twice yearly under
These have been adjusted at the factory for proper
normal conditions if sediment bowl adjacent is
alignment and must not be disturbed.
Cup Spray Pattern Check
Injector Spray Pattern - ST-668
Two models of ST668 are being used to check cup spray
patterns, the first was released in 1960 and contains
black-oxide plated seat and seat spacers; the current
tool contains "bright" cadium plated seat and seat
spacers. The latter unit can be used with all Cummins
injectors, while the earlier model cannot be used with 2
degree spray angle injector cups. To check L series
Fig. 6-1-36, F60207. PT (type D) Injector in ST668
injector cups with the latest tool, use ST849 cup seat or
black seat from original ST668 tool.
1. Locate ST668 on or near ST790 Injector Test
If you have ST668 with black oxide finish seat and
Stand, (or other source of 22 psi [152 kPa]
spacer, it may be brought up to date by purchasing
constant fuel pressure) so injector inlet
ST668, Details 36, 2, 1, 17, 18, 19, 20, 22, 23, 24, 25, 4,
connection of test stand will reach Injector to be
37 and 3 from your nearest Cummins Distributor.
spray checked. Use injector test oil or fuel oil to
The following instructions are written with the
understanding that all ST668 Spray Test Fixtures have
2. Attach drain hose to ST668 base and place
been brought uptodate.
loose end in ST790 drain pan.
3. Assemble applicable cup seat spacer (see Table
6114) to seat bracket bore.
4. Place "H2" seat . in seat spacer and bracket
bore (seat bracket bore only, if 2 deg. cups are
to be checked) or if L Series cups are to be
checked use ST849 (black) seat.
Check cup markings as shown in Fig. 6-1-40.
indicates 7 holes, 0.007 inch [.178 mm] diameter
and 17 deg. spray angle).
5. Check cup markings for number of spray holes
and place applicable target ring in base of
ST668. Target rings are marked on the "handle"
(6 and 9 holes or 5, 7 and 8 holes).
Fig. 6-1-65, F60119. ST668 spray test fixture