TM-9-2320-280-20 HMMWV Technical Manual Unit Maintenance Volume 1 Download
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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. 2-737