Unit Injector Harness Terminal Replacement

M-371-001
(August 2009)
Valid for

All Mack trucks US04 and USO7 MP7, MP8, MP10 engines.

Case description

Poor contact between the unit injector male terminals and the harness connector female terminals can result in unit
injector faults (SID 1-6, FMI 3 or FMI 5) on MACK MP7 (US04 or USO7), MP8 and MP10 engines. To correct this issue,
high-force female terminal sockets are available through the MACK Parts System.

Unit Injector Harness Connector

Note: These high-force terminals are expected to implemented into production in May, 2009.

Parts
Part numbers required are as follows:
Qty. Part number Description
24 20734499 Seal
24 21336484 High-force terminal pins, female
* 20429371 Connector body
* 983472 Tie wraps, high-temperature

* Quantity as required.
Repair

The unit injector harness terminals should be replaced if the following conditions are encountered:

e Recurrent SID 1-6, FMI 3 or FMI 5 faults
¢ Fault tracing produces no apparent solution
e Resistance checks at the affected cylinder(s) does not reveal any problems with the unit injector or wiring harness

Note: Replacement of the unit injectors is not necessary. Replacing the harness female sockets will correct the condition.

Note: To perform a proper crimp, the crimping tool shown in the illustration below must be used. DO NOT use any
crimping tool other than the one shown below.

Unit Injector Terminal Pin Replacement Tools

1. Jaws (Tool No. 88890004) 2. Crimping Tool (Tool No. 88890003)
3. Terminal Release Tool (Tool No. 9808646)

Terminal Replacement Procedures

Note: Perform the following procedures on one harness wire at a time for the connectors at all six cylinders.

It is necessary to be very precise when crimping the terminals on the harness wires. There is very little room for error, as
there is only enough wire for 1-2 replacement crimps. Splicing the unit injector harness wires is NOT permitted.

It is recommended that a few practice crimps be made on a spare piece of wire to get the “feel” of a proper crimp.

1. Disconnect the unit injector harness connectors from the unit injectors.

1. Unit Injector 2. Harness Connector

2. Cut the tie wraps that secure the unit injector harness to the cylinder head. On USO4 MP7 engines, the harness
wires are secured to the cylinder head by metal retaining clips. On these engines, slide the harness from
underneath the clips.

3. Check the wires at the entry of each connector body to ensure they are not twisted. If twisted, untwist them so they
lay flat.

Untwist Harness and Inspect Wires

4. Disengage the red secondary lock on the connector body by using a small screwdriver to slide the lock forward
until it is flush with the end of the connector.

Unlock Secondary Lock

1. Locked 2. Unlocked

5. Insert the terminal release tool (tool No. 9808646) into the terminal cavity from the front side of the connector body
and push rearward. At the same time, gently pull the wire from the back of the connector.

Insert Terminal Release Tool

6. Cut the existing terminal from the wire directly behind the crimp, and then slide the existing wire seal off the wire.
Thoroughly clean the oil from the wire with a shop rag.

Cut Terminal and Remove Seal

1. Cut Wire Directly Behind Terminal 2. Slide Seal Off End of Wire

7. Slide a new wire seal (part number 20734499) onto the end of the wire.

Install Wire Seal

1. Wire Seal (part number 20734499)

8. Strip 5 mm (3/16") of insulation from the end of the wire. If using a multihole stripping tool, use the hole which is
closest to 1 mm (3/64").

Strip Insulation from End of Wire

5 MM (3/16")

9. Slide the new wire seal to the edge of the insulation.

Note: The wire seal is there to dampen vibration only, not to prevent oil from entering the connector body.

Seal Positioned at End of Insulation

———

10. Insert a new terminal (part number 21336484) into the “B” die (middle die) of the crimping tool, making sure the
crimp wings of the terminal are fully within the crimping dies. Close the crimping tool enough to prevent the terminal
from falling out.

Proper Positioning of Terminal in Crimping Tool

11. Insert the wire and seal into the terminal until the seal is flush with the jaws of the crimp tool. Squeeze the tool
handles fully to crimp the terminal.

Insert Wire into Terminal

12. Inspect the crimp. A proper crimp should look like the crimp shown in the following illustration.

Inspect for Proper Crimp

13. Insert the terminal and wire into the connector body, pushing the terminal forward until it locks in place. Gently pull
the wire rearward to ensure it is locked in place. Use a suitable paint marker to mark the wire once it has been
inserted into the connector body to indicate the wire has been repaired.

14. Repeat the above procedures for the remaining wires in the connector, one at a time. After the four terminals have
been replaced, slide the red secondary lock back to the locked position and then continue with the remaining
connectors on the harness.

Note: DO NOT twist the harness wires when connecting the harness to the unit injector. There must be as much
slack in the wires as possible, and the wires must not rub against adjacent components.
Note: It may be noticed that more force is required to connect the harness connector to the unit injector. This is
typical for the high force terminal pins.

15. Properly route and secure the harness to the cylinder head. Use high temperature tie wraps (part number 983472)
as required.

16. After completing the repair, start the engine, check for proper operation and test for faults.

17. To signify that the unit injector harness terminals have been replaced, use a paint stick to mark a white or yellow
dot on the upper EECU connector as shown in the following illustration.

Paint Mark Upper EECU Connector

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Warranty information

Reimbursement

This Repair may be eligible for reimbursement if a product failure was experienced within the time and
mileage limits of the applicable warranty coverage. Reimbursement is obtained via normal claim handling
process.

Claim Type (used only when uploading from the Dealer Bus. Sys.) 01

Labor Code

Primary Labor Code 2228B-01-56 3.0 hr.,
Causal Part 20375186

Issued by

Technical Service

Mack Trucks, Inc. engages in a continuous program of testing and evaluating to provide the best possible product. Mack
Trucks, Inc., however, is not committed to, or liable for updating existing chassis.