DETROIT DIESEL 53
Fuel Injector 2.1.1
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 permissible.
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 needle
valve lift , use tool J 9462-01 (Fig. 15) as follows:
Zero the indicator by placing the bottom surface of the plunger assembly on a flat surface and zero the indicator
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.
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.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.
If the needle valve lift is within the limits, install a new needle valve spring and recheck the valve opening
pressure and valve action. Low valve opening pressure or poor atomization with a new spring and seat indicates the
spray tip and needle valve assembly must be replaced.
Fig. 19 - Fuel Output Check Chart
Fig 20. Position of Calibrator Fuel
Reassemble the injector as outlined under Assemble Injector and check it in the comparator or the calibrator.
FUEL OUTPUT TEST
The injector fuel output test can be performed in either the comparator J 7041 or the calibrator J 22410.
When injectors are removed from an engine for fuel output testing and, if satisfactory, reinstalled without disassembly,
extreme care should be taken to avoid reversing the fuel flow. When the fuel flow is reversed, dirt trapped by the filter is
back-flushed into the injector components.
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 adapter. The position of the fuel pipes on the comparator (Fig. 16)
depends on the adapter 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 adapter being used and the direction a
fuel flow through the injector.
NOTE: The fuel passages in adapters J 7041-61, J-7041-72 and J 7041-88 are drilled
straight through the adapters. The fuel passages in adapter J-7041-130 are cross drilled.