1996 Jaguar XJ6 will not start, bad switch, relay or module

TESTING
ON-VEHICLE TESTING
NOTE:All tests should be performed in sequence and data recorded for later reference.

Voltage Drop Tests
NOTE:Perform all tests in sequence and record data for later reference. Before performing voltage drop tests, ensure battery and battery connections are satisfactory. When performing voltage drop tests, a moving coil voltmeter (0-20 volt range) should be used. To avoid engine from starting during voltmeter checks, ensure low-voltage circuit of ignition coil is disconnected between coil and distributor.

Battery Terminal Under Load Test
To check battery terminal voltage under load, connect voltmeter across battery terminals and operate starter. See Fig. 1. If voltmeter reads about 10 volts, go to next test. A voltage reading of less than 10 volts indicates excessive current flow in circuit. Remove starter for bench testing. See BENCH TESTING.
Fig. 1: Testing Battery Terminal Voltage Under Load
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Switching Circuit Resistance Test
To check switching circuit for high resistance, connect voltmeter between solenoid operating winding terminal and ground. See Fig. 2.
NOTE:If solenoid operates intermittently during test or engine cranks at low or irregular speed, insufficient voltage at solenoid operating winding terminal exists or solenoid is faulty.

When switch contacts are closed, voltage reading should be slightly less than reading recorded in BATTERY TERMINAL UNDER LOAD TEST. A satisfactory reading indicates a negligible voltage drop in circuit, and fault is in the solenoid.
If voltage reading is considerably lower than voltage reading in BATTERY TERMINAL UNDER LOAD TEST, check switching circuit for high resistance or faulty connections.
Fig. 2: Testing Switching Circuit Resistance
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Starter Terminal Voltage Under Load Test
Having determined battery voltage under load, check voltage across starter with voltmeter connected between starter input terminal and ground. See Fig. 3.
With starter switch closed, voltage reading should not be more than.5 volt below reading recorded in BATTERY TERMINAL UNDER LOAD TEST. If reading is within this limit, starter circuit is satisfactory.
If low reading across starter exists, but voltage at battery is satisfactory, high resistance in cable or at solenoid contacts exists.
Fig. 3: Testing Starter Terminal Voltage
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Voltage Drop On Insulated Line Test
Connect voltmeter between starter input terminal and battery (insulated) terminal. See Fig. 4. When ignition is turned on, voltmeter should indicate battery voltage.
When ignition is turned off, voltmeter reading should be close to zero volts. A high voltmeter reading indicates a high resistance in starter circuit. Check all insulated connections at battery and starter.
Fig. 4: Testing Voltage Drop On Insulated Line
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Voltage Drop Across Solenoid Contacts Test
Connect voltmeter across 2 main solenoid terminals, and crank engine. A zero or fractional reading on voltmeter indicates high resistance recorded in VOLTAGE DROP ON INSULATED LINE TEST must be due either to high resistance starter cables or soldered connections (cold joint). A high reading indicates a faulty solenoid or solenoid connections.
Voltage Drop On Ground Line
Connect voltmeter between battery ground terminal and starter commutator end bracket. Voltmeter should indicate practically zero volts when starter is operated.
NOTE:The total voltage drop in starter circuit (insulated line plus ground line) must not exceed.5 volt. If meter reading is high, clean and tighten all ground connections and check ground strap. Ground strap must make good electrical contact with chassis and engine block. If strap is frayed, it will have a serious effect on performance of the starter. It can even immobilize vehicle.