Guardian Technologies 4759, 4456, 4390 TEST 60- CHECK OIL PRESSURE SWITCH AND WIRE, Section, Part

DC CONTROL

PART 4

SECTION 4.4

DIAGNOSTIC TESTS

12.Now repeat Step 11 with the negative meter test lead connected to Connector “C” (Figure 26).

13.Now check the flywheel magnet by holding a screwdriver at the extreme end of its handle and with its point down. When the tip of the screwdriver is moved to within 3/4 inch (19mm) of the magnet, the blade should be pulled in against the magnet.

14.Now check the flywheel key. The flywheel’s taper is locked on the crankshaft taper by the torque of the flywheel nut. A keyway is provided for alignment only and theoretically carries no load.

Note: If the flywheel key becomes sheared or even partially sheared, ignition timing can change. Incorrect timing can result in hard starting or failure to start.

15.As stated earlier, the armature air gap is fixed for single cylinder engine models and is not adjustable. Visually inspect the armature air gap and hold down bolts.

16.Disconnect the shutdown ground wire from the armature and retest for spark, Test 55.

17.Perform Steps 13 and 14.

RESULTS:

If sparking still does not occur after adjusting the armature air gap, testing the ground wires and performing the basic flywheel test, replace the ignition magneto(s).

TEST 60- CHECK OIL PRESSURE SWITCH

AND WIRE 86

DISCUSSION:

If the oil pressure switch contacts have failed in their closed position, the engine will probably crank and start. However, shutdown will then occur within about 5 (five) seconds. If the engine cranks and starts, then shuts down almost immediately with a LOP fault light, the cause may be one or more of the following:

❏Low engine oil level.

❏Low oil pressure.

❏A defective oil pressure switch.

If the oil pressure switch contacts have failed open or Wire 86 does not have continuity to ground at starting, the engine will not crank. If the engine does not crank, the cause may be one of the following:

❏A defective oil pressure switch stuck open.

❏An open Wire 86 to Circuit Board.

Figure 27. Oil Pressure Switch

PROCEDURE:

Note: For Problem 9 Flow Chart, perform Steps 3a, 4 and 5 only. For Problem 12 Flow Chart perform all steps.

1.Check engine crankcase oil level.

a.Check engine oil level.

b.If necessary, add the recommended oil to the dipstick FULL mark. DO NOT OVERFILL ABOVE THE FULL MARK.

2.With oil level correct, try starting the engine.

a.If engine still cranks and starts, but then shuts down, go to Step 3.

b.If engine does not crank go to Step 6.

c.If engine cranks and starts normally, discontinue tests.

3.Do the following:

a.Disconnect Wire 86 and Wire 0 from the oil pressure switch terminals. Remove the switch and install an oil pressure gauge in its place.

b.Connect Wire 86 to Wire 0 for starting purposes only. After engine starts, remove Wire 86 from Wire 0.

c.Start the engine while observing the oil pressure reading on gauge.

d.Note the oil pressure.

(1)Normal oil pressure is approximately 35-40 psi with engine running. If normal oil pressure is indicated, go to Step 4 of this test.

(2)If oil pressure is below about 4.5 psi, shut engine down immediately. A problem exists in the engine lubrication system.

Note: The oil pressure switch is rated at 10 psi for v- twin engines, and 8 psi for single cylinder engines.

4.Remove the oil pressure gauge and reinstall the oil pressure switch. Do NOT connect Wire 86 or Wire 0 to

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