DETROIT DIESEL 53
atomization is poor, the cause usually is a worn or
fatigued valve spring. Replace the spring.
If the valve opening pressure is within 2300-3300 psi.
proceed to check for spray tip seat leakage. Actuate
the pump handle several times, then hold the pressure
at 1500 psi for 15 seconds. Inspect the spray tip seat
for leakage. There should be no fuel droplets although
a slight wetting of the end of the valve tip is
If the spray tip seat is satisfactory, proceed to check
the hold time for a pressure drop of from 1500 to 1000
psi. The time should not be less than 5 seconds. If the
valve pressure drops from 1500 to 1000 psi in less than
5 seconds, replace the needle valve and tip assembly.
If the needle valve assembly passes the above test, the
needle valve lift check can be omitted. To check the
n e e d l e valve lift, use tool J 9462-01 (Fig. 15) as
Fig. 20 Position of Calibrator Fuel Flow Pipes
1. Zero the indicator by placing the bottom surface of
the plunger assembly on a flat surface and zero the
Reassemble the injector is outlined under Assemble
Injector and check i t i n t h e c o m p a r a t o r o r t h e
2. Place the spray tip and needle valve assembly tight
against the bottom of the gage with the quill of the
needle valve in the hole in the plunger.
FUEL OUTPUT TEST
3. While holding the spray tip and needle valve
assembly tight against the gage, read the needle valve
lift on the indicator. The lift should be .008 " to
The injector fuel output test can be performed in
.018" if it exceeds .018". the tip assembly must be
replaced. If it is less than .008", inspect for foreign
material between the needle valve and the tip seat.
When injectors are removed from an engine for fuel
4. If the needle valve lift is within the limits, install a
output testing and if satisfactory, reinstalled without
new needle valve spring and recheck the valve opening
disassembly, extreme care should be taken to avoid
pressure and valve action. Low valve opening pressure
reversing the fuel flow. When the fuel flow is reversed,
o r poor atomization with a new spring and seat
dirt trapped by the filter is back-flushed into the
indicates the spray tip and needle valve assembly must
Before removing an injector from the engine, note the
direction of the fuel flow. To avoid reversing the fuel
flow when checking injector fuel output, use the
appropriate adaptor. The position of the fuel pipes on
being used and the direction of fuel flow through the
injector. The position of the braided fuel inlet tube
and the plastic fuel outlet tube on the calibrator
(Fig. 20) depends on the adaptor being used and the
direction of fuel flow through the injector.
NOTE: The fuel passages in adaptors J 7041-61.
J-7041-72 and J 7041-88 are drilled straight
Fig. 19 - Fuel Output Check Chart
through the adaptors. The fuel passages in
adaptor J-7041 - 130 are cross drilled.