Guardian Technologies 4389, 4456, 4390, 4760, 4759, 4758 manual Test 58 Check Shutdown Wire

DC CONTROL

PART 4

SECTION 4.4

DIAGNOSTIC TESTS

1.Remove both spark plugs.

2.Insert a compression gauge into either cylinder.

3.Crank the engine until there is no further increase in pressure.

4.Record the highest reading obtained.

5.Repeat the procedure for the remaining cylinder and record the highest reading.

RESULTS:

The difference in pressure between the two cylinders should not exceed 25 percent. If the difference is greater than 25 percent, loss of compression in the lowest reading cylinder is indicated.

Example 1: If the pressure reading of cylinder #1 is 65 psi and of cylinder #2, 60 psi, the difference is 5 psi. Divide "5" by the highest reading (65) to obtain the percentage of 7.6 percent.

Example 2: No. 1 cylinder reads 75 psi; No. 2 cylinder reads 55 psi. The difference is 20 psi. Divide "20" by "75" to obtain "26.7" percent. Loss of compression in No. 2 cylinder is indicated.

If compression is poor, look for one or more of the following:

Loose cylinder head bolts.

Failed cylinder head gasket.

Burned valves or valve seats.

Insufficient valve clearance.

Warped cylinder head.

Warped valve stem.

Worn or broken piston ring(s).

Worn or damaged cylinder bore.

Broken connecting rod.

Worn valve seats or valves.

TEST 58 - CHECK SHUTDOWN WIRE

DISCUSSION:

Circuit board action during shutdown will ground Wire

18.Wire 18 is connected to the Ignition Magneto(s). The grounded magneto will not be able to produce spark.

PROCEDURE:

1.On v-twin generators, remove Wire 18 from the stud located above the oil cooler. On single cylinder generators, disconnect Wire 18 at the bullet connector.

2.Perform Test 55.

3.If spark now occurs with Wire 18 removed, check for a short to ground. Set the AUTO-OFF-MANUAL switch to OFF. Remove the 17 pin connector J1 from the circuit board.

4.Set a VOM to measure resistance. Connect one test lead to Wire 18 from the control panel. Connect the other test lead to a clean frame ground. INFINITY should be measured.

5.Reconnect the J1 connector to the circuit board.

6.Set a VOM to measure resistance. Connect one test lead to Wire 18 from the control panel. Connect the other test lead to a clean frame ground. Set the AUTO- OFF-MANUAL switch to MANUAL. During cranking the meter should read INFINITY.

RESULTS:

1.If INFINITY was NOT measured in Step 4, repair or replace shorted ground Wire 18 between the J1 connector from the circuit board to the stud or bullet connector.

2.If INFINITY was NOT measured in Step 6 during cranking, replace the circuit board and retest for spark.

3.If ignition spark still has not occurred, proceed to Test 59.

TEST 59 - CHECK AND ADJUST IGNITION

MAGNETOS

DISCUSSION:

In Test 55, a spark tester was used to check for engine ignition. If sparking or weak spark occurred, one possible cause might be the ignition magneto(s). This test consists of adjusting the air gap between the ignition magneto(s) and the flywheel. The flywheel and flywheel key will also be checked during this test.

PROCEDURE:

Note: The air gap between the ignition magneto and the flywheel on single cylinder engines is non- adjustable. Proceed directly to Steps 15,16 and 17 for single cylinder engines. For V-twin engines, proceed as follows.

1.See Figure 23. Rotate the flywheel until the magnet is under the module (armature) laminations.

2.Place a 0.008-0.012 inch (0.20-0.30mm) thickness gauge between the flywheel magnet and the module laminations.

3.Loosen the mounting screws and let the magnet pull the magneto down against the thickness gauge.

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