ENGINE START SWITCH - ADJUSTMENT/TEST
EFFECTIVITY
Airplanes with four position rotary start switch
1. General
A. The purpose of this test is to verify the function of all switches, solenoid, cams, springs, etc., within the four position engine start switch. This test also checks the circuitry between the start switch and the interface with the engine.
B. This test is applicable to either engine.
2. Equipment and Materials
A. Ohmmeter or continuity tester
B. Jumper wires
3. Prepare to Test Engine Start Switch
A. Open the ENGINE START IGNITION circuit breaker (28 vdc) and the ENGINE LOW ENERGY IGNITION breakers (115 vdc) on the P6-2 panel for the engine switch to be tested.
B. Open the ENGINE START VALVES breaker (28 vdc) on the P6-2 panel.
4. Test Engine Start Switch (Fig. 501)
A. Disconnect plug D420 on the ignition exciter unit for the engine switch to be tested and jumper across pins A to B and C to D. Disconnect plug D424 from the pneumatic starter valve and plug D422 from the starter cutout switch on the engine of the switch being tested.
(1) Attach an ohmmeter or continuity indicator between the load side of each of the above circuit breakers, except the ENGINE START VALVES circuit breaker, and ground in turn. Continuity shall exist in the ENGINE START IGNITION (dc) circuit when the start switch located on the pilot’s overhead panel, is in the GRD (Ground) or the FLT (Flight) position and the start lever, on the pedestal, is in the IDLE position. Remove jumper from pins A and B of plug D420. Continuity shall not exist. Continuity in the ENGINE LOW ENERGY IGNITION (ac) circuit shall exist when the start switch is in the LOW IGN position and the start lever is in the IDLE position. Remove jumper from pins C and D of plug D420. Continuity shall not exist.
Sep 20/82 74-31-12 Page 501
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
Engine Ignition Switch Test 500
74-31-12 Figure 1 Jan 20/83
Page 502
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
B. Check engine starter control circuits as follows:
(1)
With the start switch in GRD position (must be held), attach an ohmmeter or continuity indicator between the load side of the ENGINE START VALVES circuit breaker and ground. No continuity shall exist. Jumper pin A to D on plug D422. Continuity shall exist (the resistance shall not exceed 3,000 ohms). Remove jumper. Jumper pin 1 to 2 on plug D424. Continuity shall exist. Remove jumper.
(2)
Place start lever in CUTOFF position. Jumper across pins A to D on plug D422. Close the ENGINE START VALVES circuit breaker. Place the start switch in GND position. The start switch shall remain in GND position, hands off. Remove jumper from plug D422 pins A and D and the start switch shall return to OFF position automatically.
C. Remove jumpers and replace plugs and circuit breakers.
500
Sep 20/82 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 74-31-12 Page 503
ENGINE START SWITCH - ADJUSTMENT/TEST
EFFECTIVITY
Airplanes with five position rotary start switch
1. General
A. The purpose of this test is to verify the function of all switches, solenoid, cams, springs, etc., within the five position engine start switch. This test also checks the circuitry between the start switch and the interface with the engine.
B. This test is applicable to either engine.
2. Equipment and Materials
A. Ohmmeter or continuity tester
B. Jumper wires
3. Prepare to Test Engine Start Switch
A. Open the ENGINE RIGHT and LEFT IGNITION circuit breakers (115 vdc) on the P6-2 panel for the engine switch to be tested. Open ENGINE START VALVES circuit breaker (28 vdc) on the P6-2 panel.
4. Test Engine Start Switch (Fig. 501)
A. Disconnect exciter plugs D420 and D1214, disconnect plug D424 from the pneumatic starter valve and plug D422 from the starter cutout switch for the engine switch to be tested.
(1)
Jumper pin A to B on plug D420. Place start lever into CUTOFF position and the start switch to GRD position (must be held). There shall be no continuity from the load side of the ENGINE RIGHT IGNITION circuit breaker to ground.
(2)
Place the start lever into the IDLE position. There shall be continuity in the ENGINE RIGHT IGNITION circuit with start switch in GRD, R IGN or FLT positions. Remove jumper from plug D420. Continuity shall not exist.
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