Section 7

DIAGNOSTIC TESTS

TEST 33 - CHECK SPARK PLUGS

DISCUSSION:

During Test 32, if spark jumped the tester gap, the ignition system must be functioning properly. However, if the engine misses the spark plug itself may be fouled.

PROCEDURE:

Remove spark plugs. Clean with a commercial sol- vent. DO NOT BLAST CLEAN SPARK PLUGS. Replace spark plugs if badly fouled, if ceramic is cracked, or if badly worn or damaged. Set gap to 0.030 inch (0.76mm). Use a Champion RC12YC (or equivalent) replacement spark plug.

Figure 7-35 – Setting Spark Plug Gap

RESULTS:

1.Clean and regap or replace sparks plug as necessary.

2.If spark plugs are good for gasoline models, go to Test 36. For LPG models, go to Test 35.

TEST 34 - CHECK AND ADJUST IGNITION

MAGNETOS

DISCUSSION:

The ignition system used on GTV-760 engines is a solid-state (breakerless) type. The system utilizes a magnet on the engine flywheel to induce a relatively low voltage into an ignition magneto assembly. Ignition magneto internal components increase the voltage and deliver the resulting high voltage across the spark plug gap.

The ignition magneto houses a solid state-circuit board that controls ignition timing. Timing is fixed and spark advance is automatic.

Major components of the ignition system include (a) two ignition magneto assemblies, (b) the spark plugs,

(c)the engine control board and (d) the engine fly- wheel.

Solid-state components encapsulated in the ignition magneto are not accessible and cannot be serviced.

If the magneto is defective, the entire assembly must be replaced. The air gap between the magneto and the flywheel magnet is between 0.012” to 0.015”.

The ignition magneto assembly (Figure 7-36) consists of (a) ignition magneto, (b) spark plug high tension lead and (c) spark plug boot.

Figure 7-36. – Ignition Magneto Assembly

In Test 32, 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. If no sparking occurs, the ground harness may be at fault.

PROCEDURE:

1.Disconnect the J1 connector from the Engine Control Board. Carefully remove Wire 18A from Pin Location J1-4. Connect the J1 connector back to the engine control board. Repeat Test 32 “Check Ignition Spark”. If the unit now produces spark go to Step 2. If the unit does not produce spark or has weak spark go to Step 4.

2.Do the following:

a.Set a VOM to measure resistance. Connect the positive (+) meter test lead to Wire No.18A (Wire 18A still removed from the J1 connector) Connect the negative (-) meter test lead to a clean frame ground. “Infinity” should be measured, or 0.5 to 1M ohms, depending upon the type of VOM used. If “Continuity” is measured proceed to Step12.

b.Set a VOM to the diode test range. Attach the negative (-) meter test lead to Pin Location J1-4 on the Engine Control Board. (Wire 18A still removed from the J1 connec- tor) Attach the positive (+) meter test lead to frame ground. Set the Start-Stop Switch to START. “Infinity” should be measure dur- ing cranking and running. If the VOM does not have a diode test range, set VOM to measure resistance again. “Infinity” should be measured.

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Generac Power Systems 75, 55, 65 manual Test 33 Check Spark Plugs, Test 34 Check and Adjust Ignition Magnetos
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65, 75, 55 specifications

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