TM 9-2320-280-20-1
Description:
COMPRESSION UNBALANCE TEST #14 (6.2L ONLY)
This procedure compares the compression
between the highest and lowest cylinders and
displays the unbalance in percent. Test requires
DCA hookup only.
Typical Applications:
Check compression unbalance of engine with
VTM powered from battery of vehicle being
tested.
Test Procedure:
1. Set up engine to prevent Starting by disconnec-
ting wire 54A. Stop Engine. Shut off fuel before
cranking. Crank engine without fuel for 5 seconds
to dear fuel from cylinders.
2. Set TEST SELECT switches to 14.
3. Press and release TEST button.
4. Wait until GO appears on display before
proceeding.
5. When GO appears, crank engine. Display will
change to while engine is turning.
6. When OFF or E013 appears, stop cranking.
7. If OFF appears, wait for message to appear.
(A) The number displayed will be the percent
unbalance between the highest and lowest cylin-
ders. A number above 25 is a failure.
(B) If GO appears, repeat from step 2.
(C) A FAIL message usually means compression
is too far unbalanced to measure with STE/ICE.
Pre-Test Procedures:
Run Confidence Test. Warmup
engine to operating temperature.
Run first-peak series teats 72,73,74,
75.
Possible Error Messages:
E006 VTM doesn’t detect battery
Voltage.
E013 VTM cannot use date
received.
E027 Error in entry of compression
Unbalance constants.
E032 Vehicle’s cranking speed is
varying too much for a
compression unbalance
measurement.
NOTE
If E013 appears, test data cannot be
analyzed because of weak batteries,
or interrupted cranking during test.
Correct problem and repeat from
Step 2.
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