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Home › Ford › 1990 › LTD Crown Victoria S, 5.8 G › Repair and Diagnosis › Engine Performance › System › Engine Controls - System/Component Tests - 5.8L › Timing Control Systems › Spark Timing Advance

Spark Timing Advance

  1. Disconnect and plug distributor vacuum hose(s). Connect timing light and tachometer to engine. If ignition module with base part No. (-12A244-) is installed on vehicle, disconnect 2-pin connector with Yellow and Black wires. Install jumper between Yellow and Black pins of ignition module connector and go to next step. For all others, go to next step.
  2. Start engine and bring to normal operating temperature. Ensure engine speed is at or below timing RPM. Refer to Vehicle Emission Control Information Decal for specification. If engine speed is not within specifications, reset RPM to below timing RPM specification.
  3. Check and record initial ignition timing. If vehicle has factory installed Positive-Buy label attached to Vehicle Emission Control Information Decal, timing should be F 4 degrees of specification. If not, reset timing, remove or deface Positive-Buy label and go to next step. If vehicle does not have Positive-Buy label, timing should be F 2 degrees of specifications. If not, reset timing and go to next step.
  4. For vehicles that do not have ignition module with base part No. (-12A244-), go to step 6). For vehicles with ignition module base part No. (-12A244-), remove jumper installed in step 1) and reconnect connector. Recheck initial timing at timing RPM. If timing is the same as recorded in step 3), disconnect ignition module 2-pin connector (Yellow and Black wires) and go to next step. If engine dies (due to excessive spark retard) when ignition module 2-pin connector is disconnected, spark retard operation is okay. Reconnect ignition module 2-pin connector and go to step 6). If timing is not the same as recorded in step 3), diagnose MCU system then return to step 1).
  5. Recheck initial ignition timing at timing RPM. If timing is retarded from step 4), retard operation is okay. Go to step 6). If timing is not retarded from step 4), substitute new ignition module. Install jumper between Yellow and Black pins of ignition module connector and recheck initial ignition timing. If timing is the same as in step 3), return to step 4). If substitute ignition module appears to correct problem, reconnect original module to verify repair. If timing is not the same as in step 3), repeat this step.
  6. Increase engine speed to 2500 RPM and check timing. See the IGNITION TIMING ADVANCE SPECIFICATIONS table in the C - V8 SPECIFICATIONS article. If timing is not within specification, replace distributor and recheck advance operation. If timing is within specification, recheck timing at initial timing RPM. If timing is not the same as in step 3), replace distributor. If timing is the same as in step 3), mechanical advance is okay. Go to next step.
  7. Install distributor vacuum advance hose without spark delay valve (if equipped). Increase engine speed to 2500 RPM and hold for 60 seconds. Check ignition timing and return engine speed to idle. Refer to IGNITION TIMING ADVANCE SPECIFICATIONS table in the C - V8 SPECIFICATIONS article in this section. If timing is not within specification, go to next step. If timing is within specifications, vacuum advance mechanism is okay. Go to step 10).
  8. Install "T" fitting into vacuum advance hose and connect vacuum gauge to "T" fitting. Increase engine speed to 2500 RPM and hold for 60 seconds. Check vacuum gauge for presence of vacuum and return engine speed to idle. If vacuum is greater than 15 in. Hg, check diaphragm for vacuum leaks and stator assembly for binding or sticking. Repair as necessary and return to step 7). If vacuum is less than 15 in. Hg, check for vacuum solenoids or lockout devises. If vacuum solenoids or lockout devises are present, go to next step.
  9. Disconnect and plug vacuum advance hose. Attach test vacuum hose between distributor vacuum advance diaphragm connection and manifold vacuum source. Increase engine speed to 2500 RPM and hold for 60 seconds. Check timing and return engine speed to idle. Refer to IGNITION TIMING ADVANCE SPECIFICATIONS table in the C - V8 SPECIFICATIONS article in this section. If timing is within specifications, repair original vacuum source. Remove test vacuum hose and return to step 7). If timing is not within specifications, check diaphragm for vacuum leaks and stator assembly for binding or sticking. Repair as necessary. Reconnect all components and return to step 7). If distributor has dual diaphragm, go to next step. If not, spark timing advance testing complete.
  10. Disconnect and plug vacuum hose to vacuum advance. Connect vacuum hose to retard diaphragm connection. Check timing at idle RPM. If timing is retarded from step 3), spark timing advance testing complete. If timing is not retarded from step 3), reconnect vacuum hose to vacuum advance connection. Install vacuum gauge in vacuum retard hose. With engine idling, check for presence of vacuum. If a minimum vacuum of 15 in. Hg is present, replace diaphragm assembly and rerun this step. If a minimum vacuum of 15 in. Hg is not present, repair vacuum source. Rerun this step.
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