Ignition System No Start Test

Fig. 1 Coil negative terminal jumper wire:

Fig. 2 Spark control computer 10-way connector:

Fig. 3 Distributor 3-wire harness connector:

Fig. 4 Rotor shutter blades. 4-135 engine:

Before performing this test, perform the ``Ignition System Starting Test.'' Failure to do so may lead to unnecessary diagnostic time and incorrect test results.
1. With a voltmeter, measure and note battery voltage. Battery specific gravity must be at least 1.220, temperature corrected, to deliver the necessary voltage to operate the cranking and ignition systems properly.
2. Remove coil wire from distributor cap.
3. Place ignition switch in ``On'' position, then using special jumper wire, Fig. 1, momentarily ground the ignition coil negative terminal while holding the coil wire 1/4 inch from a good engine ground. A spark should be obtained.
4. If spark was obtained, proceed to step 7. If not, turn ignition Off, then disconnect 10-way, electrical connector at Spark Control Computer, Fig. 2. Do not remove grease from harness connector or connector cavity since grease is used to prevent moisture from corroding the terminals. There must be at least 1/8 inch of grease on bottom of computer connector cavity. If not, apply a liberal amount of Mopar Multi-purpose grease, part number 2932524 or equivalent over end of connector plug before installation.
5. Turn ignition On, hold wire 1/4 inch from ground and momentarily ground coil negative terminal using jumper wire, Fig. 1. If spark is present, replace Spark Control Computer. If spark is not present, measure voltage at coil positive terminal using suitable voltmeter. Voltage reading should be within one volt of battery voltage.
6. If no voltage was obtained at coil positive terminal, check for open circuit between battery and coil and repair as necessary. If voltage was obtained, measure voltage at coil negative terminal. Reading should be within one volt of battery voltage. If no voltage is present or voltage is present but spark is not, replace coil.
7. If spark was obtained in step 2, but engine will not start, hold open carburetor switch with thin piece of paper and measure voltage at carburetor switch. Reading should be at least 5 volts on 1983 models, or within one volt of battery voltage on 1984-87 models. If voltage reading is satisfactory, proceed to step 11. If no voltage is present, turn ignition Off, then disconnect 10-way connector from Spark Control Computer.
8. Turn ignition On and measure voltage between connector cavity 2 and ground, Fig. 2. Reading should be within one volt of battery voltage. If not, check for continuity between battery and cavity 2 using ohmmeter. If continuity is not present, check for open circuit between battery and cavity 2 and repair as necessary.
9. If battery voltage is present in step 8, turn ignition Off and check continuity between carburetor switch and cavity 7 on 10-way connector. If continuity is not present, check for open circuit between cavity 7 and carburetor switch and repair as necessary.
10. If continuity is present in step 9, check continuity between cavity 10 and ground. If continuity is present, replace Spark Control Computer. If continuity is not present between cavity 10 and ground, check for damaged wiring or an open circuit and repair as necessary. If wiring is satisfactory, but engine will not start, proceed to step 11.
11. Reconnect 10-way connector into Spark Control Computer, turn ignition On and hold coil wire 1/4 inch from ground. Disconnect distributor electrical connector and momentarily connect jumper wire between terminals 2 and 3 of connector, Fig. 3. Spark should be observed at coil wire.
12. If spark is present at coil wire, but engine will not start, replace pickup assembly and perform rotor test as described in step 18. On 4-135 engines, when replacing Hall effect pickup assembly, check to ensure rotor shutter blades are grounded, Fig. 4. Connect one lead of suitable ohmmeter to shutter blade and other lead to ground. If continuity is not present, press downward on rotor shaft and recheck continuity. If continuity is still not present, replace rotor. Check to ensure that new rotor is marked ESA on top. Do not start engine until continuity has been obtained.
13. If no spark is present at coil wire check voltage between cavity 1 of distributor connector and ground, Fig. 3. Reading obtained should be within one volt of battery voltage. If battery voltage is not present, proceed to step 15. If battery voltage is present, turn ignition off and disconnect 10-way connector from Spark Advance Computer. Check for continuity between cavity 2 of distributor connector, Fig. 3, and cavity 9 of 10-way connector, Fig. 2. Repeat procedure between cavity 3 of distributor connector and cavity 5 of 10-way connector.
14. If continuity is not present, open circuit exists in harness wiring. Repair as necessary. If continuity is present, replace Spark Advance Computer.
15. If no battery voltage is present at cavity A of distributor connector, turn ignition Off, then disconnect 10-way connector from Spark Control Computer.
16. Check for continuity between cavity 1 of distributor connector and cavity 3 of 10-way connector. If continuity is not present, repair open circuit in wire between cavities as necessary.
17. If continuity is present turn ignition On and check for voltage between cavity 2 and 10 of 10-way connector. If battery voltage is present, replace Spark Control Computer. If battery voltage is not present, check for proper computer ground circuit connection and repair as necessary.
18. To perform rotor test, check to ensure that rotor is stamped ESA on top. Turn ignition Off, then using suitable ohmmeter, check for good rotor ground contact at distributor shaft. If continuity is indicated, rotor is satisfactory. If continuity is not indicated, check to ensure that rotor is properly seated on shaft.