Ignition System - Hei-Est Chevrolet Camaro III рестайлинг

DESCRIPTION

The Delco-Remy High Energy Ignition system with Electronic Spark Timing (HEI/EST) is a self contained unit. The distributor consists of housing, rotor, cap, magnetic pick-up, pole piece and pick-up coil. On some models, ignition coils are contained within the distributor cap and other models have an externally mounted coil. (Scheme 2)and (Scheme 3). A capacitor is installed for radio noise suppression.

All spark timing changes are controlled by the Electronic Control Module (ECM). No vacuum or centrifugal advance mechanisms are used. Some models use an additional ignition retard circuit in the event of engine detonation (knock). Distributors with externally mounted ignition coils are equipped with sealed module connectors. (Scheme 3)

Typical HEI/EST Distributor Integral coil system shown. Scheme 2

When the external teeth on the timing core approach, align with and pass the internal teeth on pole piece, an alternating current is induced in the pick-up coil windings. This alternating current signals switching transistors in the HEI module to make or break the ignition coil primary ground circuit. When the primary ground circuit is removed, the magnetic field created by the flow of current in the primary windings collapses across the primary and secondary windings of the coil. This induces a high-voltage surge in the secondary windings of the coil. Secondary voltage is then discharged to the rotor which distributes it to the appropriate spark plug terminal. The distributor module may have 2 different terminal arrangements depending on application.

Distributor with Sealed Module Connectors External coil system shown. Scheme 3

EST SYSTEM

The ECM monitors information concerning crankshaft position, engine RPM, engine load, atmospheric conditions, engine temperature, and transmission gear position. This information is used by the ECM to compute desired spark timing which is relayed to the distributor, enabling appropriate changes to ignition timing. A back-up spark advance system is incorporated to signal ignition module in the event of ECM failure.

The distributor module is connected to ECM by a 4-wire EST connector which performs the following functions

1. Terminal "A" of the 4-wire connector triggers the HEI module. The ECM advances or retards spark on this terminal based on calculations involving the reference signal from terminal "B" and other sensor input signals. (Scheme 4) If base timing is incorrectly set, entire advance curve will be incorrect.
2. Terminal "B" of the 4-wire connector supplies RPM data and crankshaft position reference to the distributor. If wire is open or grounded on fuel injected models, engine will not run.
3. Terminal "C" of the 4-wire connector is the by-pass circuit. At approximately 400 RPM, ECM applies 5 volts to this circuit which switches spark timing control from HEI module to ECM. On some models, this by-pass wire contains a connector located between the 4-wire connector and the ECM. This is disconnected when adjusting base timing. On all models, an open or grounded by-pass circuit will set a Code 42 in ECM memory. The engine will run at base timing plus a small amount of advance built into the HEI module.
4. Terminal "D" of the 4-wire connector is the reference ground. It is grounded to distributor and ensures there is no voltage drop which could affect performance.

Typical HEI/EST Distributor Circuitry. Scheme 4

SENSORS

The coolant temperature sensor signals ECM to advance timing on a cold engine and return timing to programmed advance curve as engine reaches normal operating temperature. If engine overheats, spark is retarded to prevent detonation. During light throttle operation, throttle position sensor input to ECM allows for additional advance.

Spark advance is also governed by input from engine RPM and Manifold Absolute Pressure (MAP) sensor. When MAP output voltage is low (high vacuum), ECM gives less spark advance. More spark advance is given when MAP output voltage is high (low vacuum).

On engines with port fuel injection, ECM will calculate spark advance using information from Mass Airflow (MAF) sensor, coolant temperature sensor and engine RPM. When engine is under minimum load, based on low RPM and low mass airflow signals, less spark advance is given. When engine is under heavy load based on high RPM and high mass airflow signals, increased spark advance is given.

ELECTRONIC SPARK CONTROL (ESC) SYSTEM

The basic components of Electronic Spark Control (ESC) system are detonation (knock) sensor, HEI/EST distributor, controller (on some models) and ECM. On some fuel injected models, the function of the ESC controller is built into the Memory Calibration (MEM-CAL) unit of the ECM.

On controller-equipped systems, when detonation (knock) occurs, sensor sends an electrical signal to controller. Controller will then remove the signal voltage from the ECM-monitored knock signal wire. When the ECM senses a voltage drop (to less than one volt) on the knock sensor signal line, spark timing will be retarded. The ECM will retard spark timing until signals from detonation sensor cease.

On vehicles using ECMs containing MEM-CAL units, the ECM supplies and monitors a 5-volt reference signal on the knock sensor signal line. Internal circuitry of the knock sensor will pull this voltage down to about 2.5 volts. When knock occurs, the knock sensor produces an AC voltage signal which rides on the 2.5-volt DC signal. The voltage and frequency of this signal depend upon knock signals received by the sensor. The ECM will retard spark timing until signals from detonation sensor cease.

Typical Electronic Spark Control (ESC) Circuitry. Scheme 5

ADJUSTMENTS

The only adjustments that can be made to HEI/EST ignition system are basic ignition timing and spark plug gap.

DIAGNOSIS

If reference or EST signals are interrupted due to an open circuit or a faulty ECM, HEI/EST module will provide a timing signal based on engine RPM. Engine may continue to run, although less efficiently. If by-pass signal is lost, by-pass switch will direct RPM information directly to coil rather than to ECM.

Normally, 5-15 seconds after starting a warm engine, by-pass signal from ECM will operate a by-pass switch in HEI/EST module. The HEI/EST module's RPM-controlled timing signal will switch over and RPM signal will flow directly to the ECM for processing.

Loss of EST signal from ECM when 5-volt by-pass signal is present will cause engine to stop because HEI/EST module is no longer sending signals directly to ignition coil. Any loss of EST signal will stop all flow to coil. If vehicle is restarted, engine will run for a few seconds and stop when by-pass signal comes back on.

External Ignition Coil (Sealed Module Connector Distributor)

Remove coil connectors and secondary coil wire. In test "A", use high ohmmeter scale. (Scheme 6) If continuity is present, replace coil. In test "B", use low ohmmeter scale. Reading should be very low or near zero volts. If not, replace coil. In test "C", use high ohmmeter scale. If there is no continuity, replace coil.

Testing Ignition Coil Resistance External coil system is shown. Scheme 6

Integrally Mounted Ignition Coil

1. Turn ignition off. Remove the distributor cap and coil assembly. Turn upside down. (Scheme 7) Set ohmmeter to low scale. Connect leads to coil "BAT" and "TACH" terminals. If resistance exceeds one ohm, replace ignition coil.
2. Set ohmmeter on high scale. Connect one lead to coil secondary terminal and the other lead first to "TACH" terminal and then to ground terminal. If resistance reading in BOTH instances is infinity, replace ignition coil.

Testing Ignition Coil Resistance Integral coil system is shown. Scheme 7

DISTRIBUTOR PICK-UP COIL SHORT & RESISTANCE CHECKS

1. Disconnect pick-up coil leads from HEI/EST module terminals "N" and "P". Set ohmmeter to middle scale and connect one lead to either pick-up coil lead and the other lead to distributor housing. Flex pick-up coil leads by hand to check for intermittent shorts to ground. Reading should be infinity at all times. If not, replace pick-up coil.
2. Connect ohmmeter between both pick-up coil leads. Check for intermittent opens by flexing wires and connectors. Resistance should be 500-1500 ohms. If not, replace pick-up coil.

Checking Distributor Pick-Up Coil Integral coil system is shown.External coil testing is similar. Scheme 8

IGNITION SYSTEM CHECK

Note. Before testing, obtain Spark Tester (ST-125). If tachometer is connected to ignition coil "TACH" terminal, disconnect it before performing tests. When performing tests, use digital voltmeter with at least 10-megohm input impedance.

1. Remove any spark plug wire and attach Spark Tester (ST-125). Check for spark while cranking engine. If there is no spark, check at other wires in same manner. If there is still no spark, proceed to step 2). If spark occurs, ignition system is not at fault. Check fuel system, spark plugs and engine mechanical condition for cause of a no-start condition.
2. Disconnect 4-wire EST connector between distributor and ECM. Check for spark at tester. If spark is present, replace pick-up coil.
3. If no spark occurred with 4-wire plug disconnected, check voltage at distributor "BAT" terminal while cranking engine.
4. If "BAT" terminal reading was less than 7 volts, repair primary circuit back to ignition switch. If reading was 7 volts or more, leave negative lead grounded and check voltage at "TACH" terminal.
5. If "TACH" terminal reading was less than one volt, ignition coil or ignition coil connector is defective. Repair or replace as necessary. If reading is 10 volts or more, proceed to step 7).
6. If "TACH" terminal voltage was 1-10 volts, replace distributor HEI/EST module and check for spark with spark tester connected as described in step 7). If a spark occurs, ignition system is functioning. If there is no spark, replace ignition coil.
7. If "TACH" terminal voltage in step 5) was 10 volts or more, attach Spark Tester (ST-125) to coil output terminal inside distributor cap using a modified spark plug boot. Using a jumper wire, ground the spark tester. (Scheme 9) Crank engine and check for spark. If no spark occurs, proceed to step 9). NOTE: Leave Spark Tester (ST-125) connected in this manner during remainder of tests.
8. If spark occurs, check color match of pick-up coil connector and ignition coil lead. Inspect cap for water, cracks or other damage. If no damage is noted, replace rotor. NOTE: Ignition coils with Red "BAT" lead and White "TACH" lead should be matched with pick-up coils having either a Clear, Black or Blue connector. Ignition coils with Red "BAT" lead and Yellow "TACH" lead must be matched with pick-up coils with Yellow connector.
9. Remove pick-up coil leads from module. Connect positive lead of voltmeter to coil "TACH" terminal and negative lead to ground. Turn ignition switch to "ON" position. Connect lead of test light to battery positive terminal. Touch test light probe (maximum of 5 seconds) to HEI/EST module terminal "P". Watch voltmeter as test light touches terminal.
10. If voltage drops, proceed to step 11). If voltage does not drop, check module ground. Also check for open circuits in wires from distributor coil to HEI/EST module. If okay, replace HEI/EST module.
11. Using spark tester still connected as in step 7), check for spark when test light is removed from module terminal. If spark occurs, the pick-up coil or its connections are defective. Perform «DISTRIBUTOR PICK-UP COIL SHORT & RESISTANCE CHECKS»(/chevrolet/camaro/iii-1985-1992/remont/ignition-system/#ignition-system-hei-est__distributor-pick-up-coil-short-resistance) in this article.
12. Ensure ignition coil is properly grounded. Use Distributor Module Tester (J-26792) to check HEI/EST module. Replace module if defective. If module tests okay, test coil wire and replace if necessary. If coil wire tests okay, replace ignition coil.
13. If no module tester is available, replace ignition coil with a known good unit and return to step 11). If spark occurs, problem was faulty ignition coil. If no spark occurs, original ignition coil is okay. Reinstall original ignition coil and replace HEI/EST module.

Integral Coil Spark Tester (ST-125) Hook-Up. Scheme 9

Sealed Module Connector Distributor w/External Ignition Coil

1. Disconnect a spark plug wire at plug end and connect Spark Tester (ST-125). Check for spark while cranking engine. If no spark occurs, check for spark at other wires. Intermittent sparks are considered no spark. If no spark occurs, proceed to step 2). If spark occurs, ignition system is not at fault. Check fuel system, spark plugs and engine mechanical condition for cause of a no-start condition.
2. Unplug 4-wire EST connector. Check for spark at tester. If spark occurs, replace pick-up coil. If no spark occurs, check for spark with spark tester connected at coil tower while cranking engine. (Scheme 10) NOTE: Leave Spark Tester (ST-125) connected in this manner during remainder of tests.
3. If spark is present while cranking, inspect cap for cracks or other defects. If okay, replace rotor. If no spark occurs while cranking, disconnect distributor 2-wire "C/+" (coil) connector. Turn ignition on and check voltage at "+" and "C" terminals of harness connector.
4. If there is less than 10 volts at terminal "C", check for open or short to ground in circuit from terminal "C" to ignition coil. If circuit is okay, fault is ignition coil or coil connection. If both terminals read less than 10 volts, proceed to step 5). If both terminals read 10 volts or more, proceed to step 6).
5. Repair wire from module "+" terminal to "B" terminal of Black ignition coil connector or primary circuit to ignition switch.
6. Reconnect distributor 2-wire connector. Check voltage from "TACH" lead to ground with ignition on. "TACH" lead may be taped back to harness.
7. If voltage is less than one volt in step 6), repair open tachometer lead or connector and repeat step 6). If voltage reading is 1-10 volts in step 6), replace module and check for spark as described in step 11). If spark is present, system is good. If no spark occurs, replace ignition coil.
8. If voltage is more than 10 volts in step 6), connect test light from "TACH" lead to ground. Crank engine and observe light. If light blinks, replace ignition coil and recheck for spark with spark tester. If no spark, reinstall original coil and replace ignition module.
9. If light remains steady in step 8), unplug distributor 4-wire connector. Remove distributor cap and pick-up coil connector at module. Turn ignition on.
10. Connect voltmeter between "TACH" terminal and ground. Insulate test light probe to within 1/4" of tip. Note voltage as test light is momentarily connected between module terminal "P" and a 1.5-8 volt source. To ensure against module damage, DO NOT allow test light to be connected for more than a moment.
11. If there is no voltage drop, ensure module is properly grounded. If good ground is noted, replace module. If voltage drops, check for spark at coil tower with spark tester when test light is removed from module terminal "P".
12. If spark is present in step 11), ensure rotating pole piece is magnetized, replace if necessary. If pole piece is magnetized, check pick-up coil resistance or connections, (resistance should be 500-1500 ohms). If no spark occurs in step 11), check module with Module Tester (J-24642). Replace module if defective. Check coil wire. If wire is okay, replace coil.
13. If module tester was not available, replace ignition coil with a known good unit and repeat step 10). If spark is present, system is okay. If no spark is present, original ignition coil was okay. Reinstall original coil and check coil wire. If coil wire is okay, replace ignition module.

External Coil Spark Tester (ST-125) Hook-Up. Scheme 10

INTERMITTENT OPERATION CHECK

1. Check fuel system, spark plug wires, distributor cap, and spark plugs. Most intermittent problems are caused by faulty electrical connections. Visually inspect wiring for a fault. Drive vehicle with a voltmeter connected to a suspected circuit.
2. Using a "Scan" tester, monitor input signals. See SCAN TESTER USAGE and SCAN DATA tables in appropriate CEC TESTS W/CODES article in the ENGINE PERFORMANCE section. Refer to the following list. Check for electrical system interference caused by a defective relay, ECM driven solenoid or switch causing a sharp electrical surge. Problem should occur when faulty component is operated. If problem ceases when component is disconnected, component is at fault.
3. Check for improper installation of electrical options such as lights, radios, etc. Check for open diode(s) across A/C compressor clutch and other possible defective diodes. For 2.8L, see: «2.8L VIN [W] PFI CEC TESTS W/CODES»(ref-94880) For 5.0L Carbureted, see: «5.0L/5.7L CARBURETOR CEC TESTS»(ref-94886) For 5.0L TBI, see: «5.0L VIN [E] TBI CEC TESTS W/CODES»(/chevrolet/camaro/iii-1985-1992/remont/testing-diagnostics/#50l-vin-e-tbi-tests-wcodes) For 5.0L PFI, see: «5.0L/5.7L VINS [F,8] PFI CEC TESTS W/CODES»(/chevrolet/camaro/iii-1985-1992/remont/testing-diagnostics/#50l57l-vins-f8-pfi-cec-tests-wcodes) For 5.7L Carbureted, see: «5.0L/5.7L CARBURETOR CEC TESTS»(ref-94886) For 5.7L PFI, see: «5.0L/5.7L VINS [F,8] PFI CEC TESTS W/CODES»(/chevrolet/camaro/iii-1985-1992/remont/testing-diagnostics/#50l57l-vins-f8-pfi-cec-tests-wcodes) For Cadillac Brougham, see: «CCC 5.0L CARBURETOR TESTS W/CODES»(ref-50249) For All other Cadillac with DFI, see: «DFI ECM TESTS W/CODES»(ref-94889)

Carbureted Engines

1. With transmission in Park of Neutral, run engine at fast idle. Note timing change as ALDL "Test" terminal is grounded. (Scheme 11) If timing changes, system is operating properly. CAUTION: Prior to placing automatic transmission in Drive in following step, ensure emergency brake is FIRMLY applied and DRIVE wheels are securely blocked.
2. If timing does not change on vehicles with manual transmissions, go to step 3). If timing does not change on vehicles with automatic transmissions, let engine return to idle. Place transmission in Drive and note timing change as "Test" terminal is grounded. If timing changes, system is operating properly.
3. If no change in timing occurs, check voltage at output of MAP sensor or vacuum sensor as vacuum hose is removed and reinstalled. If no change occurs, problem is in the vacuum or MAP sensor circuit. If voltage output changes, proceed to step 4).
4. On vehicles with automatic transmission, disconnect Park/Neutral switch and recheck for timing change. If timing changes, problem is either an improperly adjusted or faulty Park/Neutral switch. If timing does not change, check for grounded Park/Neutral signal wire between ECM and Park/Neutral switch. If wire is not grounded, replace ECM. Prior to replacement of ECM, see ECM REPLACEMENT in the appropriate CEC TESTS W/CODES article in the ENGINE PERFORMANCE section. Refer to the following list. For 2.8L, see: «2.8L VIN [W] PFI CEC TESTS W/CODES»(ref-94880) For 5.0L Carbureted, see: «5.0L/5.7L CARBURETOR CEC TESTS»(ref-94886) For 5.0L TBI, see: «5.0L VIN [E] TBI CEC TESTS W/CODES»(/chevrolet/camaro/iii-1985-1992/remont/testing-diagnostics/#50l-vin-e-tbi-tests-wcodes) For 5.0L PFI, see: «5.0L/5.7L VINS [F,8] PFI CEC TESTS W/CODES»(/chevrolet/camaro/iii-1985-1992/remont/testing-diagnostics/#50l57l-vins-f8-pfi-cec-tests-wcodes) For 5.7L Carbureted, see: «5.0L/5.7L CARBURETOR CEC TESTS»(ref-94886) For 5.7L PFI, see: «5.0L/5.7L VINS [F,8] PFI CEC TESTS W/CODES»(/chevrolet/camaro/iii-1985-1992/remont/testing-diagnostics/#50l57l-vins-f8-pfi-cec-tests-wcodes) For Cadillac Brougham, see: «CCC 5.0L CARBURETOR TESTS W/CODES»(ref-50249) For All other Cadillac with DFI, see: «DFI ECM TESTS W/CODES»(ref-94889)

Fuel Injected Engines

The ECM will set timing at a specified value when the ALDL "Test" terminal is grounded. (Scheme 11) Note timing when terminal is not grounded. Ground "Test" terminal and check for timing change at 2000 RPM. If timing changes, the EST is operating properly.

Typical ALDL Connector Location. Scheme 11

Note. For more information on specific ALDL connector locations, see the appropriate CEC TESTS W/CODES article in the ENGINE PERFORMANCE section. Refer to the following list.

1. For 2.8L, see: «2.8L VIN [W] PFI CEC TESTS W/CODES»(ref-94880)
2. For 5.0L Carbureted, see: «5.0L/5.7L CARBURETOR CEC TESTS»(ref-94886)
3. For 5.0L TBI, see: «5.0L VIN [E] TBI CEC TESTS W/CODES»(/chevrolet/camaro/iii-1985-1992/remont/testing-diagnostics/#50l-vin-e-tbi-tests-wcodes)
4. For 5.0L PFI, see: «5.0L/5.7L VINS [F,8] PFI CEC TESTS W/CODES»(/chevrolet/camaro/iii-1985-1992/remont/testing-diagnostics/#50l57l-vins-f8-pfi-cec-tests-wcodes)
5. For 5.7L Carbureted, see: «5.0L/5.7L CARBURETOR CEC TESTS»(ref-94886)
6. For 5.7L PFI, see: «5.0L/5.7L VINS [F,8] PFI CEC TESTS W/CODES»(/chevrolet/camaro/iii-1985-1992/remont/testing-diagnostics/#50l57l-vins-f8-pfi-cec-tests-wcodes)
7. For Cadillac Brougham, see: «CCC 5.0L CARBURETOR TESTS W/CODES»(ref-50249)
8. For All other Cadillac with DFI, see: «DFI ECM TESTS W/CODES»(ref-94889)

ESC PERFORMANCE CHECK

Note. Perform these tests for complaints of poor performance/fuel economy or detonation (knock). Perform checks only after checking ignition timing, MAP and EGR operation or if engine overheats. If Code 43 is set in ECM memory, perform appropriate DIAGNOSTIC CIRCUIT CHECK in the appropriate CEC TESTS W/CODES article in the ENGINE PERFORMANCE section. Refer to the following list.

1. For 2.8L, see: «2.8L VIN [W] PFI CEC TESTS W/CODES»(ref-94880)
2. For 5.0L Carbureted, see: «5.0L/5.7L CARBURETOR CEC TESTS»(ref-94886)
3. For 5.0L TBI, see: «5.0L VIN [E] TBI CEC TESTS W/CODES»(/chevrolet/camaro/iii-1985-1992/remont/testing-diagnostics/#50l-vin-e-tbi-tests-wcodes)
4. For 5.0L PFI, see: «5.0L/5.7L VINS [F,8] PFI CEC TESTS W/CODES»(/chevrolet/camaro/iii-1985-1992/remont/testing-diagnostics/#50l57l-vins-f8-pfi-cec-tests-wcodes)
5. For 5.7L Carbureted, see: «5.0L/5.7L CARBURETOR CEC TESTS»(ref-94886)
6. For 5.7L PFI, see: «5.0L/5.7L VINS [F,8] PFI CEC TESTS W/CODES»(/chevrolet/camaro/iii-1985-1992/remont/testing-diagnostics/#50l57l-vins-f8-pfi-cec-tests-wcodes)
7. For Cadillac Brougham, see: «CCC 5.0L CARBURETOR TESTS W/CODES»(ref-50249)
8. For All other Cadillac with DFI, see: «DFI ECM TESTS W/CODES»(ref-94889)

ESC Controller Equipped Models

1. Connect tachometer to engine. Block DRIVE wheels. FIRMLY apply parking brake. Place transmission in Park or Neutral. Run engine at fast idle (about 1500 RPM). With engine at normal operating temperature, tap engine block in area of detonation sensor. If RPM drops, system is operating properly.
2. If RPM does not drop, disconnect harness from ESC controller (located in engine compartment) and check for RPM change. If there is no change in RPM, proceed to step 5). If RPM drops, run engine at 2000 RPM. Connect a digital voltmeter between disconnected ESC harness connector terminals "E" and "D". Voltage should not exceed .08 volt on the AC scale.
3. If voltage reading is correct, problem is a faulty ESC connection or ESC controller. If voltage is not correct, check for an open in wire from ESC controller connector terminal "D" to ground.
4. Repair wire if an open is found. If no open wire is found, check for an open or poor connection between detonation sensor and ESC controller connector terminal "E". If circuit is okay, replace detonation sensor.
5. Inspect "SERVICE ENGINE SOON" light. If light is on, problem is a faulty ESC controller or detonation sensor, proceed to step 7). If light is off, turn ignition switch to "ON" position (engine not running) and check voltage from ground to ESC terminal "C".
6. If voltage is less than 2 volts, replace ECM. If voltage is greater than 2 volts, repair short to voltage in wire from ESC terminal "C" to ECM knock signal terminal.
7. If light was on in step 5), reconnect ESC controller. With engine idling, disconnect knock sensor. Note timing change.
8. If timing increases, check for source of engine knock. If knock is not present, replace knock sensor. If timing did not increase in step 7), disconnect terminal "E" from controller connector and once again note timing change.
9. If timing does not increase in step 8), replace ESC controller. If timing did increase, circuit to knock sensor is picking up induced signals. Move sensor signal wire away from other electrical circuits (i.e. spark plug or alternator wiring). NOTE: If Code 43 is set in ECM memory, see appropriate CODE 43 chart in the appropriate CEC TESTS W/CODES article in the ENGINE PERFORMANCE section. Refer to the following list. For 2.8L, see: «2.8L VIN [W] PFI CEC TESTS W/CODES»(ref-94880) For 5.0L Carbureted, see: «5.0L/5.7L CARBURETOR CEC TESTS»(ref-94886) For 5.0L TBI, see: «5.0L VIN [E] TBI CEC TESTS W/CODES»(/chevrolet/camaro/iii-1985-1992/remont/testing-diagnostics/#50l-vin-e-tbi-tests-wcodes) For 5.0L PFI, see: «5.0L/5.7L VINS [F,8] PFI CEC TESTS W/CODES»(/chevrolet/camaro/iii-1985-1992/remont/testing-diagnostics/#50l57l-vins-f8-pfi-cec-tests-wcodes) For 5.7L Carbureted, see: «5.0L/5.7L CARBURETOR CEC TESTS»(ref-94886) For 5.7L PFI, see: «5.0L/5.7L VINS [F,8] PFI CEC TESTS W/CODES»(/chevrolet/camaro/iii-1985-1992/remont/testing-diagnostics/#50l57l-vins-f8-pfi-cec-tests-wcodes) For Cadillac Brougham, see: «CCC 5.0L CARBURETOR TESTS W/CODES»(ref-50249) For All other Cadillac with DFI, see: «DFI ECM TESTS W/CODES»(ref-94889)

Non-controller Equipped

1. With engine at normal operating temperature, increase engine speed to about 1500 RPM. Tap on engine lift hook bracket while observing engine timing. If timing retards system is operating properly.
2. If timing did not retard in step 1), disconnect knock sensor. Connect voltmeter positive lead to knock sensor and negative lead to ground. Set voltmeter on 2-volt AC scale.
3. Tap on engine block near knock sensor. Voltage should be indicated while tapping on block. If voltage is indicated, check for improper installation of MEM-CAL. If installed properly, replace faulty MEM-CAL or ECM. If voltage is not indicated, replace knock sensor.

REMOVAL & INSTALLATION

Removal and installation information not available.

OVERHAUL

Overhaul information is not available.

See also:
• 5.0L VIN [E] TBI CEC TESTS W/CODES
• 5.0L/5.7L VINS [F,8] PFI CEC TESTS W/CODES
• DISTRIBUTOR PICK-UP COIL SHORT & RESISTANCE CHECKS